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Configuring and managing networking

Red Hat Enterprise Linux

Managing network interfaces, firewalls, and advanced networking features

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Abstract

The networking capabilities of Red Hat Enterprise Linux (RHEL) enable you to configure your host to meet your organization’s network and security requirements. You can configure Bonds, VLANs, bridges, tunnels and other network types to connect the host to the network.

You can build complex and performance-critical firewalls for the local host and the entire network. Packet filtering software, such as the firewalld service, the nftables framework, and Express Data Path (XDP).

RHEL also supports advanced networking features. For example, with policy-based routing, you can set up complex routing scenarios, and MultiPath TCP (MPTCP) enables clients to roam among different networks without interrupting the TCP connection to the application running on your RHEL server.

Making open source more inclusive

Red Hat is committed to replacing problematic language in our code, documentation, and web properties. We are beginning with these four terms: master, slave, blacklist, and whitelist. Because of the enormity of this endeavor, these changes will be implemented gradually over several upcoming releases. For more details, see our CTO Chris Wright’s message.

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Chapter 1. Consistent network interface device naming

The Linux kernel assigns names to network interfaces by combining a fixed prefix and a number that increases as the kernel initializes the network devices. For instance, eth0 represents the first device being probed on start-up. If you add another network interface card to the system, the assignment of the kernel device names is no longer fixed. Consequently, after a reboot, the kernel can name the device differently.

To solve this problem, the udev device manager supports a number of different naming schemes. By default, udev assigns fixed names based on firmware, topology, and location information. This has the following advantages:

Device names are fully predictable.
Device names stay fixed even if you add or remove hardware, because no re-enumeration takes place.
Defective hardware can be seamlessly replaced.

Warning

Red Hat does not support systems with consistent device naming disabled. For further details, see Is it safe to set net.ifnames=0?

1.1. Network interface device naming hierarchy

If consistent device naming is enabled, which is the default in Red Hat Enterprise Linux, the udev device manager generates device names based on the following schemes:

SchemeDescriptionExample

Device names incorporate firmware or BIOS-provided index numbers for onboard devices. If this information is not available or applicable, udev uses scheme 2.

eno1

Device names incorporate firmware or BIOS-provided PCI Express (PCIe) hot plug slot index numbers. If this information is not available or applicable, udev uses scheme 3.

ens1

Device names incorporate the physical location of the connector of the hardware. If this information is not available or applicable, udev uses scheme 5.

enp2s0

Device names incorporate the MAC address. Red Hat Enterprise Linux does not use this scheme by default, but administrators can optionally use it.

enx525400d5e0fb

The traditional unpredictable kernel naming scheme. If udev cannot apply any of the other schemes, the device manager uses this scheme.

eth0

By default, Red Hat Enterprise Linux selects the device name based on the NamePolicy setting in the /usr/lib/systemd/network/99-default.link file. The order of the values in NamePolicy is important. Red Hat Enterprise Linux uses the first device name that is both specified in the file and that udev generated.

If you manually configured udev rules to change the name of kernel devices, those rules take precedence.

1.2. How the network device renaming works

By default, consistent device naming is enabled in Red Hat Enterprise Linux. The udev device manager processes different rules to rename the devices. The udev service processes these rules in the following order:

The /usr/lib/udev/rules.d/60-net.rules file defines that the /lib/udev/rename_device helper utility searches for the HWADDR parameter in /etc/sysconfig/network-scripts/ifcfg-* files. If the value set in the variable matches the MAC address of an interface, the helper utility renames the interface to the name set in the DEVICE parameter of the file.
The /usr/lib/udev/rules.d/71-biosdevname.rules file defines that the biosdevname utility renames the interface according to its naming policy, provided that it was not renamed in the previous step.
The /usr/lib/udev/rules.d/75-net-description.rules file defines that udev examines the network interface device and sets the properties in udev-internal variables that will be processed in the next step. Note that some of these properties might be undefined.
The /usr/lib/udev/rules.d/80-net-setup-link.rules file calls the net_setup_link udev built-in which then applies the policy. The following is the default policy that is stored in the /usr/lib/systemd/network/99-default.link file:
```
[Link]
NamePolicy=kernel database onboard slot path
MACAddressPolicy=persistent
```
With this policy, if the kernel uses a persistent name, udev does not rename the interface. If the kernel does not use a persistent name, udev renames the interface to the name provided by the hardware database of udev. If this database is not available, Red Hat Enterprise Linux falls back to the mechanisms described above.

Alternatively, set the NamePolicy parameter in this file to mac for media access control (MAC) address-based interface names.
The /usr/lib/udev/rules.d/80-net-setup-link.rules file defines that udev renames the interface based on the udev-internal parameters in the following order:
1. ID_NET_NAME_ONBOARD
2. ID_NET_NAME_SLOT
3. ID_NET_NAME_PATH
If one parameter is not set, udev uses the next one. If none of the parameters are set, the interface is not renamed.

Steps 3 and 4 implement the naming schemes 1 to 4 described in Network interface device naming hierarchy.

Additional resources

Customizing the prefix of Ethernet interfaces during the installation
systemd.link(5) man page

1.3. Predictable network interface device names on the x86_64 platform explained

When the consistent network device name feature is enabled, the udev device manager creates the names of devices based on different criteria. The interface name starts with a two-character prefix based on the type of interface:

en for Ethernet
wl for wireless LAN (WLAN)
ww for wireless wide area network (WWAN)

Additionally, one of the following is appended to one of the above-mentioned prefix based on the schema the udev device manager applies:

o <on-board_index_number>
s<hot_plug_slot_index_number>[f<function>][d<device_id>]

Note that all multi-function PCI devices have the [f<function>] number in the device name, including the function 0 device.
x <MAC_address>
[P<domain_number>]p<bus>s<slot>[f<function>][d<device_id>]

The [P<domain_number>] part defines the PCI geographical location. This part is only set if the domain number is not 0.
[P<domain_number>]p<bus>s<slot>[f<function>][u<usb_port>][…][c<config>][i<interface>]

For USB devices, the full chain of port numbers of hubs is composed. If the name is longer than the maximum (15 characters), the name is not exported. If there are multiple USB devices in the chain, udev suppresses the default values for USB configuration descriptors (c1) and USB interface descriptors (i0).

1.4. Predictable network interface device names on the System z platform explained

When the consistent network device name feature is enabled, the udev device manager on the System z platform creates the names of devices based on the bus ID. The bus ID identifies a device in the s390 channel subsystem.

For a channel command word (CCW) device, the bus ID is the device number with a leading 0.n prefix where n is the subchannel set ID.

Ethernet interfaces are named, for example, enccw0.0.1234. Serial Line Internet Protocol (SLIP) channel-to-channel (CTC) network devices are named, for example, slccw0.0.1234.

Use the znetconf -c or the lscss -a commands to display available network devices and their bus IDs.

Red Hat Enterprise Linux also supports predictable and persistent interface names for RDMA over Converged Ethernet (RoCE) Express PCI functions. Two identifiers provide predictable interface names: user identifier (UID) and function identifier (FID). On a system to get UID-based predictable interface names, enforce UID uniqueness, which is the preferred naming scheme. If no unique UIDs are available, then RHEL uses FIDs to set predictable interface names.

1.5. Customizing the prefix of Ethernet interfaces during the installation

You can customize the prefix of Ethernet interface names during the Red Hat Enterprise Linux installation.

Important

Red Hat does not support customizing the prefix using the prefixdevname utility on already deployed systems.

After the RHEL installation, the udev service names Ethernet devices <prefix>.<index>. For example, if you select the prefix net, RHEL names Ethernet interfaces net0, net1, and so on.

Prerequisites

The prefix you want to set meets the following requirements:
- It consists of ASCII characters.
- It is an alpha-numeric string.
- It is shorter than 16 characters.
- It does not conflict with any other well-known prefix used for network interface naming, such as eth, eno, ens, and em.

Procedure

Boot the Red Hat Enterprise Linux installation media.
In the boot manager:
1. Select the Install Red Hat Enterprise Linux <version>
  entry, and press
  
  Tab
  
  to edit the entry.
2. Append net.ifnames.prefix= <prefix>
  to the kernel options.
3. Press
  
  Enter
  
  to start the installer.
Install Red Hat Enterprise Linux.

Verification

After the installation, display the Ethernet interfaces:

ip link show

... 2:

net0

: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 00:53:00:c5:98:1c brd ff:ff:ff:ff:ff:ff 3:

net1

: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 00:53:00:c2:39:9e brd ff:ff:ff:ff:ff:ff ...

1.6. Assigning user-defined network interface names using udev rules

The udev device manager supports a set of rules to customize the interface names.

Procedure

Display all network interfaces and their MAC addresses:

ip link list

enp6s0f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether b4:96:91:14:ae:58 brd ff:ff:ff:ff:ff:ff enp6s0f1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether b4:96:91:14:ae:5a brd ff:ff:ff:ff:ff:ff enp4s0f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 00:90:fa:6a:7d:90 brd ff:ff:ff:ff:ff:ff

Create the file /etc/udev/rules.d/70-custom-ifnames.rules with the following contents:

SUBSYSTEM=="net",ACTION=="add",ATTR{address}=="
b4:96:91:14:ae:58
",ATTR{type}=="1
",NAME="provider0
"
SUBSYSTEM=="net",ACTION=="add",ATTR{address}=="
b4:96:91:14:ae:5a
",ATTR{type}=="1
",NAME="provider1
"
SUBSYSTEM=="net",ACTION=="add",ATTR{address}=="
00:90:fa:6a:7d:90
",ATTR{type}=="1
",NAME="dmz
"

These rules match the MAC address of the network interfaces and rename them to the name given in the NAME property. In these examples, ATTR{type} parameter value 1 defines that the interface is of type Ethernet.

Verification

Reboot the system.
```
# reboot
```

Verify that interface names for each MAC address match the value you set in the NAME parameter of the rule file:

ip link show

provider0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000 link/ether b4:96:91:14:ae:58 brd ff:ff:ff:ff:ff:ff altname enp6s0f0 provider1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000 link/ether b4:96:91:14:ae:5a brd ff:ff:ff:ff:ff:ff altname enp6s0f1 dmz: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000 link/ether 00:90:fa:6a:7d:90 brd ff:ff:ff:ff:ff:ff altname enp4s0f0

Additional resources

udev(7) man page
udevadm(8) man page
/usr/src/kernels/ <kernel_version>
/include/uapi/linux/if_arp.h provided by the kernel-doc package

1.7. Assigning user-defined network interface names using systemd link files

Create a naming scheme by renaming network interfaces to provider0.

Procedure

Display all interfaces names and their MAC addresses:

ip link show

For naming the interface with MAC address b4:96:91:14:ae:58 to provider0, create the /etc/systemd/network/70-custom-ifnames.link file with following contents:
```
[Match]
MACAddress=
b4:96:91:14:ae:58


[Link]
Name=
provider0
```
This link file matches a MAC address and renames the network interface to the name set in the Name parameter.

Verification

Reboot the system:
```
# reboot
```

Verify that the device with the MAC address you specified in the link file has been assigned to provider0:

ip link show

provider0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000 link/ether b4:96:91:14:ae:58 brd ff:ff:ff:ff:ff:ff

Additional resources

systemd.link(5) man page

Chapter 2. Configuring an Ethernet connection

Red Hat Enterprise Linux provides administrators different options to configure Ethernet connections. For example:

Use nmcli to configure connections on the command line.
Use nmtui to configure connections in a text-based user interface.
Use RHEL System Roles to automate the configuration of connections on one or multiple hosts.
Use the GNOME Settings menu or nm-connection-editor application to configure connections in a graphical interface.
Use nmstatectl to configure connections through the Nmstate API.

Note

If you want to manually configure Ethernet connections on hosts running in the Microsoft Azure cloud, disable the cloud-init service or configure it to ignore the network settings retrieved from the cloud environment. Otherwise, cloud-init will override on the next reboot the network settings that you have manually configured.

2.1. Configuring a static Ethernet connection using nmcli

To configure an Ethernet connection on the command line, use the nmcli utility.

For example, the procedure below creates a NetworkManager connection profile for the enp7s0 device with the following settings:

A static IPv4 address – 192.0.2.1 with a /24 subnet mask
A static IPv6 address – 2001:db8:1::1 with a /64 subnet mask
An IPv4 default gateway – 192.0.2.254
An IPv6 default gateway – 2001:db8:1::fffe
An IPv4 DNS server – 192.0.2.200
An IPv6 DNS server – 2001:db8:1::ffbb
A DNS search domain – example.com

Prerequisites

A physical or virtual Ethernet device exists in the server’s configuration.

Procedure

Add a new NetworkManager connection profile for the Ethernet connection:
```
# nmcli connection add con-name 
Example-Connection
 ifname enp7s0
 type ethernet
```
The further steps modify the Example-Connection connection profile you created.

Set the IPv4 address:

nmcli connection modify

Example-Connection

ipv4.addresses
192.0.2.1/24

Set the IPv6 address:

nmcli connection modify

Example-Connection

ipv6.addresses
2001:db8:1::1/64

Set the IPv4 and IPv6 connection method to manual:

nmcli connection modify

Example-Connection

ipv4.method manual

nmcli connection modify

Example-Connection

ipv6.method manual

Set the IPv4 and IPv6 default gateways:

nmcli connection modify

Example-Connection

ipv4.gateway
192.0.2.254

nmcli connection modify

Example-Connection

ipv6.gateway
2001:db8:1::fffe

Set the IPv4 and IPv6 DNS server addresses:

nmcli connection modify

Example-Connection

ipv4.dns "
192.0.2.200
"

nmcli connection modify

Example-Connection

ipv6.dns "
2001:db8:1::ffbb
"

To set multiple DNS servers, specify them space-separated and enclosed in quotes.

Set the DNS search domain for the IPv4 and IPv6 connection:

nmcli connection modify

Example-Connection

ipv4.dns-search
example.com

nmcli connection modify

Example-Connection

ipv6.dns-search
example.com

Activate the connection profile:

nmcli connection up

Example-Connection

Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/

)

Verification steps

Display the status of the devices and connections:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp7s0

ethernet

connected

Example-Connection

Use the ping utility to verify that this host can send packets to other hosts:
```
# ping 
host_name_or_IP_address
```

Troubleshooting

Make sure that the network cable is plugged-in to the host and a switch.
Check whether the link failure exists only on this host or also on other hosts connected to the same switch.
Verify that the network cable and the network interface are working as expected. Perform hardware diagnosis steps and replace defect cables and network interface cards.
If the configuration on the disk does not match the configuration on the device, starting or restarting NetworkManager creates an in-memory connection that reflects the configuration of the device. For further details and how to avoid this problem, see NetworkManager duplicates a connection after restart of NetworkManager service.

Additional resources

nm-settings(5) man page
nmcli(1) man page
Configuring NetworkManager to avoid using a specific profile to provide a default gateway

2.2. Configuring a static Ethernet connection using the nmcli interactive editor

You can configure an Ethernet connection on the command line using the interactive mode of the nmcli utility.

For example, the procedure below creates a NetworkManager connection profile for the enp7s0 device with the following settings:

A static IPv4 address – 192.0.2.1 with a /24 subnet mask
A static IPv6 address – 2001:db8:1::1 with a /64 subnet mask
An IPv4 default gateway – 192.0.2.254
An IPv6 default gateway – 2001:db8:1::fffe
An IPv4 DNS server – 192.0.2.200
An IPv6 DNS server – 2001:db8:1::ffbb
A DNS search domain – example.com

Prerequisites

A physical or virtual Ethernet device exists in the server’s configuration.

Procedure

To add a new NetworkManager connection profile for the Ethernet connection, and starting the interactive mode, enter:
```
# nmcli connection edit type ethernet con-name 
Example-Connection
```

Set the network interface:

nmcli> set connection.interface-name enp7s0

Set the IPv4 address:
```
nmcli> set ipv4.addresses 192.0.2.1/24
```

Set the IPv6 address:

nmcli> set ipv6.addresses 2001:db8:1::1/64

Set the IPv4 and IPv6 connection method to manual:

nmcli> set ipv4.method manual
nmcli> set ipv6.method manual

Set the IPv4 and IPv6 default gateways:

nmcli> set ipv4.gateway 192.0.2.254
nmcli> set ipv6.gateway 2001:db8:1::fffe

Set the IPv4 and IPv6 DNS server addresses:
```
nmcli> set ipv4.dns 192.0.2.200
nmcli> set ipv6.dns 2001:db8:1::ffbb
```
To set multiple DNS servers, specify them space-separated and enclosed in quotation marks.

Set the DNS search domain for the IPv4 and IPv6 connection:

nmcli> set ipv4.dns-search example.com
nmcli> set ipv6.dns-search example.com

Save and activate the connection:

nmcli> save persistent
Saving the connection with 'autoconnect=yes'. That might result in an immediate activation of the connection.
Do you still want to save? (yes/no) [yes] yes

Leave the interactive mode:
```
nmcli> quit
```

Verification steps

Display the status of the devices and connections:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp7s0

ethernet

connected

Example-Connection

Use the ping utility to verify that this host can send packets to other hosts:
```
# ping 
host_name_or_IP_address
```

Troubleshooting

Make sure that the network cable is plugged-in to the host and a switch.
Check whether the link failure exists only on this host or also on other hosts connected to the same switch.
Verify that the network cable and the network interface are working as expected. Perform hardware diagnosis steps and replace defect cables and network interface cards.
If the configuration on the disk does not match the configuration on the device, starting or restarting NetworkManager creates an in-memory connection that reflects the configuration of the device. For further details and how to avoid this problem, see NetworkManager duplicates a connection after restart of NetworkManager service.

Additional resources

nm-settings(5) man page
nmcli(1) man page
Configuring NetworkManager to avoid using a specific profile to provide a default gateway

2.3. Configuring a static Ethernet connection using nmtui

The nmtui application provides a text-based user interface for NetworkManager. You can use nmtui to configure an Ethernet connection with a static IP address on a host without a graphical interface.

Note

In nmtui:

Navigate by using the cursor keys.
Press a button by selecting it and hitting

Enter

.
Select and deselect checkboxes by using

Space

.

Prerequisites

A physical or virtual Ethernet device exists in the server’s configuration.

Procedure

If you do not know the network device name you want to use in the connection, display the available devices:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp7s0

ethernet unavailable -- ...

Start nmtui:
```
# nmtui
```
Select Edit a connection, and press

Enter

.
Press the Add button.
Select Ethernet from the list of network types, and press

Enter

.
Optional: Enter a name for the NetworkManager profile to be created.
Enter the network device name into the Device field.
Configure the IPv4 and IPv6 address settings in the IPv4 configuration and IPv6 configuration areas:
1. Press the Automatic button, and select Manual from the displayed list.
2. Press the Show button next to the protocol you want to configure to display additional fields.
3. Press the Add button next to Addresses, and enter the IP address and the subnet mask in Classless Inter-Domain Routing (CIDR) format.
  
  If you do not specify a subnet mask, NetworkManager sets a /32 subnet mask for IPv4 addresses and /64 for IPv6 addresses.
4. Enter the address of the default gateway.
5. Press the Add button next to DNS servers, and enter the DNS server address.
6. Press the Add button next to Search domains, and enter the DNS search domain.
Figure 2.1. Example of an Ethernet connection with static IP address settings
Press the OK button to create and automatically activate the new connection.
Press the Back button to return to the main menu.
Select Quit, and press

Enter

to close the nmtui application.

Verification

Display the status of the devices and connections:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp7s0

ethernet

connected

Example-Connection

Use the ping utility to verify that this host can send packets to other hosts:
```
# ping 
host_name_or_IP_address
```

Troubleshooting

Make sure that the network cable is plugged-in to the host and a switch.
Check whether the link failure exists only on this host or also on other hosts connected to the same switch.
Verify that the network cable and the network interface are working as expected. Perform hardware diagnosis steps and replace defect cables and network interface cards.
If the configuration on the disk does not match the configuration on the device, starting or restarting NetworkManager creates an in-memory connection that reflects the configuration of the device. For further details and how to avoid this problem, see NetworkManager duplicates a connection after restart of NetworkManager service.

Additional resources

Configuring NetworkManager to avoid using a specific profile to provide a default gateway

2.4. Configuring a static Ethernet connection using nmstatectl

To configure an Ethernet connection using the Nmstate API, use the nmstatectl utility.

For example, the procedure below creates a NetworkManager connection profile for the enp7s0 device with the following settings:

A static IPv4 address – 192.0.2.1 with the /24 subnet mask
A static IPv6 address – 2001:db8:1::1 with the /64 subnet mask
An IPv4 default gateway – 192.0.2.254
An IPv6 default gateway – 2001:db8:1::fffe
An IPv4 DNS server – 192.0.2.200
An IPv6 DNS server – 2001:db8:1::ffbb
A DNS search domain – example.com

The nmstatectl utility ensures that, after setting the configuration, the result matches the configuration file. If anything fails, nmstatectl automatically rolls back the changes to avoid leaving the system in an incorrect state.

The procedure defines the interface configuration in YAML format. Alternatively, you can also specify the configuration in JSON format.

Prerequisites

A physical or virtual Ethernet device exists in the server’s configuration.
The nmstate package is installed.

Procedure

Create a YAML file, for example ~/create-ethernet-profile.yml, with the following contents:

---
interfaces:
- name: enp7s0
  type: ethernet
  state: up
  ipv4:
    enabled: true
    address:
    - ip: 192.0.2.1
      prefix-length: 24
    dhcp: false
  ipv6:
    enabled: true
    address:
    - ip: 2001:db8:1::1
      prefix-length: 64
    autoconf: false
    dhcp: false
routes:
  config:
  - destination: 0.0.0.0/0
    next-hop-address: 192.0.2.254
    next-hop-interface: enp7s0
  - destination: ::/0
    next-hop-address: 2001:db8:1::fffe
    next-hop-interface: enp7s0
dns-resolver:
  config:
    search:
    - example.com
    server:
    - 192.0.2.200
    - 2001:db8:1::ffbb

Apply the settings to the system:

nmstatectl apply ~/create-ethernet-profile.yml

Verification steps

Display the status of the devices and connections:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp7s0

ethernet

connected

enp7s0

Display all settings of the connection profile:

nmcli connection show

enp7s0

connection.id:

enp7s0

connection.uuid:

b6cdfa1c-e4ad-46e5-af8b-a75f06b79f76

connection.stable-id: -- connection.type: 802-3-ethernet connection.interface-name:

enp7s0

...

Display the connection settings in YAML format:
```
# nmstatectl show 
enp7s0
```

Additional resources

nmstatectl(8) man page
/usr/share/doc/nmstate/examples/ directory

2.5. Configuring a static Ethernet connection using RHEL System Roles with the interface name

You can remotely configure an Ethernet connection using the network RHEL System Role.

For example, the procedure below creates a NetworkManager connection profile for the enp7s0 device with the following settings:

A static IPv4 address – 192.0.2.1 with a /24 subnet mask
A static IPv6 address – 2001:db8:1::1 with a /64 subnet mask
An IPv4 default gateway – 192.0.2.254
An IPv6 default gateway – 2001:db8:1::fffe
An IPv4 DNS server – 192.0.2.200
An IPv6 DNS server – 2001:db8:1::ffbb
A DNS search domain – example.com

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on them.
The hosts or host groups on which you to want run this playbook are listed in the Ansible inventory file.

A physical or virtual Ethernet device exists in the server’s configuration.
The managed nodes use NetworkManager to configure the network.

Procedure

Create a playbook file, for example ~/ethernet-static-IP.yml, with the following content:

---
- name: Configure the network
  hosts: managed-node-01.example.com
  tasks:
  - name: Configure an Ethernet connection with static IP
    include_role:
      name: rhel-system-roles.network

    vars:
      network_connections:
        - name: enp7s0
          interface_name: enp7s0
          type: ethernet
          autoconnect: yes
          ip:
            address:
              - 192.0.2.1/24
              - 2001:db8:1::1/64
            gateway4: 192.0.2.254
            gateway6: 2001:db8:1::fffe
            dns:
              - 192.0.2.200
              - 2001:db8:1::ffbb
            dns_search:
              - example.com
          state: up

Run the playbook:

ansible-playbook

~/ethernet-static-IP.yml

Additional resources

/usr/share/ansible/roles/rhel-system-roles.network/README.md file

2.6. Configuring a static Ethernet connection using RHEL System Roles with a device path

You can remotely configure an Ethernet connection using the network RHEL System Role.

You can identify the device path with the following command:

# udevadm info /sys/class/net/
<device_name>
 | grep ID_PATH=

For example, the procedure below creates a NetworkManager connection profile with the following settings for the device that matches the PCI ID 0000:00:0[1-3].0 expression, but not 0000:00:02.0:

A static IPv4 address – 192.0.2.1 with a /24 subnet mask
A static IPv6 address – 2001:db8:1::1 with a /64 subnet mask
An IPv4 default gateway – 192.0.2.254
An IPv6 default gateway – 2001:db8:1::fffe
An IPv4 DNS server – 192.0.2.200
An IPv6 DNS server – 2001:db8:1::ffbb
A DNS search domain – example.com

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on them.
The hosts or host groups on which you want to run this playbook are listed in the Ansible inventory file.

A physical or virtual Ethernet device exists in the server’s configuration.
The managed nodes use NetworkManager to configure the network.

Procedure

Create a playbook file, for example ~/ethernet-static-IP.yml, with the following content:

--- - name: Configure the network hosts:

managed-node-01.example.com

tasks: - name: Configure an Ethernet connection with dynamic IP include_role: name: rhel-system-roles.network vars: network_connections: - name:

example

match: path: -

pci-0000:00:0[1-3].0

&!pci-0000:00:02.0

type: ethernet autoconnect:

yes

ip: address: -

192.0.2.1/24

2001:db8:1::1/64

gateway4:

192.0.2.254

gateway6:

2001:db8:1::fffe

dns: -

192.0.2.200

2001:db8:1::ffbb

dns_search: -

example.com

state:

The match parameter in this example defines that Ansible applies the play to devices that match PCI ID 0000:00:0[1-3].0, but not 0000:00:02.0. For further details about special modifiers and wild cards you can use, see the match parameter description in the /usr/share/ansible/roles/rhel-system-roles.network/README.md file.

Run the playbook:

ansible-playbook

~/ethernet-static-IP.yml

Additional resources

/usr/share/ansible/roles/rhel-system-roles.network/README.md file

2.7. Configuring a dynamic Ethernet connection using nmcli

To configure an Ethernet connection on the command line, use the nmcli utility. For connections with dynamic IP address settings, NetworkManager requests the IP settings for the connection from a DHCP server.

Prerequisites

A physical or virtual Ethernet device exists in the server’s configuration.
A DHCP server is available in the network.

Procedure

Add a new NetworkManager connection profile for the Ethernet connection:

nmcli connection add con-name

Example-Connection

ifname
enp7s0
type ethernet

Optionally, change the host name NetworkManager sends to the DHCP server when using the Example-Connection profile:
```
# nmcli connection modify 
Example-Connection
 ipv4.dhcp-hostname Example
 ipv6.dhcp-hostname Example
```
Optionally, change the client ID NetworkManager sends to an IPv4 DHCP server when using the Example-Connection profile:
```
# nmcli connection modify 
Example-Connection
 ipv4.dhcp-client-id client-ID
```
Note that there is no dhcp-client-id parameter for IPv6. To create an identifier for IPv6, configure the dhclient service.

Verification steps

Display the status of the devices and connections:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp7s0

ethernet

connected

Example-Connection

Use the ping utility to verify that this host can send packets to other hosts:
```
# ping 
host_name_or_IP_address
```

Troubleshooting

Make sure that the network cable is plugged-in to the host and a switch.
Check whether the link failure exists only on this host or also on other hosts connected to the same switch.
Verify that the network cable and the network interface are working as expected. Perform hardware diagnosis steps and replace defect cables and network interface cards.
If the configuration on the disk does not match the configuration on the device, starting or restarting NetworkManager creates an in-memory connection that reflects the configuration of the device. For further details and how to avoid this problem, see NetworkManager duplicates a connection after restart of NetworkManager service.

Additional resources

dhclient(8) man page
nm-settings(5)
nmcli(1) man page
Configuring NetworkManager to avoid using a specific profile to provide a default gateway

2.8. Configuring a dynamic Ethernet connection using the nmcli interactive editor

You can configure an Ethernet connection on the command line using the interactive mode of the nmcli utility. For connections with dynamic IP address settings, NetworkManager requests the IP settings for the connection from a DHCP server.

Prerequisites

A physical or virtual Ethernet device exists in the server’s configuration.
A DHCP server is available in the network.

Procedure

To add a new NetworkManager connection profile for the Ethernet connection, and starting the interactive mode, enter:
```
# nmcli connection edit type ethernet con-name Example-Connection
```

Set the network interface:

nmcli> set connection.interface-name enp7s0

Optionally, change the host name NetworkManager sends to the DHCP server when using the Example-Connection profile:
```
nmcli> set ipv4.dhcp-hostname Example
nmcli> set ipv6.dhcp-hostname Example
```
Optionally, change the client ID NetworkManager sends to an IPv4 DHCP server when using the Example-Connection profile:
```
nmcli> set ipv4.dhcp-client-id client-ID
```
Note that there is no dhcp-client-id parameter for IPv6. To create an identifier for IPv6, configure the dhclient service.

Save and activate the connection:

nmcli> save persistent
Saving the connection with 'autoconnect=yes'. That might result in an immediate activation of the connection.
Do you still want to save? (yes/no) [yes] yes

Leave the interactive mode:
```
nmcli> quit
```

Verification steps

Display the status of the devices and connections:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp7s0

ethernet

connected

Example-Connection

Use the ping utility to verify that this host can send packets to other hosts:
```
# ping 
host_name_or_IP_address
```

Troubleshooting

Make sure that the network cable is plugged-in to the host and a switch.
Check whether the link failure exists only on this host or also on other hosts connected to the same switch.
Verify that the network cable and the network interface are working as expected. Perform hardware diagnosis steps and replace defect cables and network interface cards.
If the configuration on the disk does not match the configuration on the device, starting or restarting NetworkManager creates an in-memory connection that reflects the configuration of the device. For further details and how to avoid this problem, see NetworkManager duplicates a connection after restart of NetworkManager service.

Additional resources

nm-settings(5) man page
nmcli(1) man page
Configuring NetworkManager to avoid using a specific profile to provide a default gateway

2.9. Configuring a dynamic Ethernet connection using nmtui

The nmtui application provides a text-based user interface for NetworkManager. You can use nmtui to configure an Ethernet connection with a dynamic IP address on a host without a graphical interface.

Note

In nmtui:

Navigate by using the cursor keys.
Press a button by selecting it and hitting

Enter

.
Select and deselect checkboxes by using

Space

.

Prerequisites

A physical or virtual Ethernet device exists in the server’s configuration.
A DHCP server is available in the network.

Procedure

If you do not know the network device name you want to use in the connection, display the available devices:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp7s0

ethernet unavailable -- ...

Start nmtui:
```
# nmtui
```
Select Edit a connection, and press

Enter

.
Press the Add button.
Select Ethernet from the list of network types, and press

Enter

.
Optional: Enter a name for the NetworkManager profile to be created.
Enter the network device name into the Device field.
Press the OK button to create and automatically activate the new connection.
Press the Back button to return to the main menu.
Select Quit, and press

Enter

to close the nmtui application.

Verification

Display the status of the devices and connections:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp7s0

ethernet

connected

Example-Connection

Use the ping utility to verify that this host can send packets to other hosts:
```
# ping 
host_name_or_IP_address
```

Troubleshooting

Make sure that the network cable is plugged-in to the host and a switch.
Check whether the link failure exists only on this host or also on other hosts connected to the same switch.
Verify that the network cable and the network interface are working as expected. Perform hardware diagnosis steps and replace defect cables and network interface cards.
If the configuration on the disk does not match the configuration on the device, starting or restarting NetworkManager creates an in-memory connection that reflects the configuration of the device. For further details and how to avoid this problem, see NetworkManager duplicates a connection after restart of NetworkManager service.

Additional resources

Configuring NetworkManager to avoid using a specific profile to provide a default gateway

2.10. Configuring a dynamic Ethernet connection using nmstatectl

To configure an Ethernet connection using the Nmstate API, use the nmstatectl utility. For connections with dynamic IP address settings, NetworkManager requests the IP settings for the connection from a DHCP server.

The procedure defines the interface configuration in YAML format. Alternatively, you can also specify the configuration in JSON format.

Prerequisites

A physical or virtual Ethernet device exists in the server’s configuration.
A DHCP server is available in the network.
The nmstate package is installed.

Procedure

Create a YAML file, for example ~/create-ethernet-profile.yml, with the following contents:

---
interfaces:
- name: enp7s0
  type: ethernet
  state: up
  ipv4:
    enabled: true
    auto-dns: true
    auto-gateway: true
    auto-routes: true
    dhcp: true
  ipv6:
    enabled: true
    auto-dns: true
    auto-gateway: true
    auto-routes: true
    autoconf: true
    dhcp: true

Apply the settings to the system:

nmstatectl apply ~/create-ethernet-profile.yml

Verification steps

Display the status of the devices and connections:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp7s0

ethernet

connected

enp7s0

Display all settings of the connection profile:

nmcli connection show

enp7s0

connection.id:

enp7s0

_ connection.uuid:

b6cdfa1c-e4ad-46e5-af8b-a75f06b79f76

connection.stable-id: -- connection.type: 802-3-ethernet connection.interface-name:

enp7s0

...

Display the connection settings in YAML format:
```
# nmstatectl show 
enp7s0
```

Additional resources

nmstatectl(8) man page
/usr/share/doc/nmstate/examples/ directory

2.11. Configuring a dynamic Ethernet connection using RHEL System Roles with the interface name

You can remotely configure an Ethernet connection using the network RHEL System Role. For connections with dynamic IP address settings, NetworkManager requests the IP settings for the connection from a DHCP server.

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on them.
The hosts or host groups on which you want to run this playbook are listed in the Ansible inventory file.

A physical or virtual Ethernet device exists in the server’s configuration.
A DHCP server is available in the network
The managed nodes use NetworkManager to configure the network.

Procedure

Create a playbook file, for example ~/ethernet-dynamic-IP.yml, with the following content:

--- - name: Configure the network hosts:

managed-node-01.example.com

tasks: - name: Configure an Ethernet connection with dynamic IP include_role: name: rhel-system-roles.network vars: network_connections: - name: enp7s0 interface_name: enp7s0 type: ethernet autoconnect: yes ip: dhcp4: yes auto6: yes state: up

Run the playbook:

ansible-playbook

~/ethernet-dynamic-IP.yml

Additional resources

/usr/share/ansible/roles/rhel-system-roles.network/README.md file

2.12. Configuring a dynamic Ethernet connection using RHEL System Roles with a device path

You can identify the device path with the following command:

# udevadm info /sys/class/net/
<device_name>
 | grep ID_PATH=

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on them.
The hosts or host groups on which you want to run this playbook are listed in the Ansible inventory file.

A physical or virtual Ethernet device exists in the server’s configuration.
A DHCP server is available in the network.
The managed hosts use NetworkManager to configure the network.

Procedure

Create a playbook file, for example ~/ethernet-dynamic-IP.yml, with the following content:

--- - name: Configure the network hosts:

managed-node-01.example.com

tasks: - name: Configure an Ethernet connection with dynamic IP include_role: name: rhel-system-roles.network vars: network_connections: - name: example match: path: - pci-0000:00:0[1-3].0 - &!pci-0000:00:02.0 type: ethernet autoconnect: yes ip: dhcp4: yes auto6: yes state: up

Run the playbook:

ansible-playbook

~/ethernet-dynamic-IP.yml

Additional resources

/usr/share/ansible/roles/rhel-system-roles.network/README.md file

2.13. Configuring an Ethernet connection using control-center

Ethernet connections are the most frequently used connections types in physical or virtual machines. If you use Red Hat Enterprise Linux with a graphical interface, you can configure this connection type in the GNOME control-center.

Note that control-center does not support as many configuration options as the nm-connection-editor application or the nmcli utility.

Prerequisites

A physical or virtual Ethernet device exists in the server’s configuration.
GNOME is installed.

Procedure

Press the

Super

key, enter Settings, and press

Enter

.
Select Network in the navigation on the left.
Click the

+

button next to the Wired entry to create a new profile.
Optional: Set a name for the connection on the Identity tab.
On the IPv4 tab, configure the IPv4 settings. For example, select method Manual, set a static IPv4 address, network mask, default gateway, and DNS server:
On the IPv6 tab, configure the IPv6 settings. For example, select method Manual, set a static IPv6 address, network mask, default gateway, and DNS server:
Click the

Add

button to save the connection. The GNOME control-center automatically activates the connection.

Verification steps

Display the status of the devices and connections:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp7s0

ethernet

connected

Example-Connection

Use the ping utility to verify that this host can send packets to other hosts:
```
# ping 
host_name_or_IP_address
```

Troubleshooting steps

Make sure that the network cable is plugged-in to the host and a switch.
Check whether the link failure exists only on this host or also on other hosts connected to the same switch.
Verify that the network cable and the network interface are working as expected. Perform hardware diagnosis steps and replace defect cables and network interface cards.
If the configuration on the disk does not match the configuration on the device, starting or restarting NetworkManager creates an in-memory connection that reflects the configuration of the device. For further details and how to avoid this problem, see NetworkManager duplicates a connection after restart of NetworkManager service.

Additional Resources

Configuring NetworkManager to avoid using a specific profile to provide a default gateway

2.14. Configuring an Ethernet connection using nm-connection-editor

Ethernet connections are the most frequently used connection types in physical or virtual servers. If you use Red Hat Enterprise Linux with a graphical interface, you can configure this connection type using the nm-connection-editor application.

Prerequisites

A physical or virtual Ethernet device exists in the server’s configuration.
GNOME is installed.

Procedure

Open a terminal, and enter:
```
$ nm-connection-editor
```
Click the

+

button to add a new connection.
Select the Ethernet connection type, and click

Create

.
On the General tab:
1. To automatically enable this connection when the system boots or when you restart the NetworkManager service:
  1. Select Connect automatically with priority.
  2. Optional: Change the priority value next to Connect automatically with priority.
    
    If multiple connection profiles exist for the same device, NetworkManager enables only one profile. By default, NetworkManager activates the last-used profile that has auto-connect enabled. However, if you set priority values in the profiles, NetworkManager activates the profile with the highest priority.
2. Clear the All users may connect to this network check box if the profile should be available only to the user that created the connection profile.
On the Ethernet tab, select a device and, optionally, further Ethernet-related settings.
On the IPv4 Settings tab, configure the IPv4 settings. For example, set a static IPv4 address, network mask, default gateway, and DNS server:
On the IPv6 Settings tab, configure the IPv6 settings. For example, set a static IPv6 address, network mask, default gateway, and DNS server:
Save the connection.
Close nm-connection-editor.

Verification steps

Display the status of the devices and connections:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp7s0

ethernet

connected

Example-Connection

Use the ping utility to verify that this host can send packets to other hosts:
```
# ping 
host_name_or_IP_address
```

Additional Resources

Configuring NetworkManager to avoid using a specific profile to provide a default gateway

2.15. Changing the DHCP client of NetworkManager

By default, NetworkManager uses its internal DHCP client. However, if you require a DHCP client with features that the built-in client does not provide, you can alternatively configure NetworkManager to use dhclient.

Note that RHEL does not provide dhcpcd and, therefore, NetworkManager can not use this client.

Procedure

Create the /etc/NetworkManager/conf.d/dhcp-client.conf file with the following content:
```
[main]
dhcp=dhclient
```
You can set the dhcp parameter to internal (default) or dhclient.
If you set the dhcp parameter to dhclient, install the dhcp-client package:
```
# yum install dhcp-client
```
Restart NetworkManager:
```
# systemctl restart NetworkManager
```
Note that the restart temporarily interrupts all network connections.

Verification

Search in the /var/log/messages log file for an entry similar to the following:
```
Apr 26 09:54:19 server
 NetworkManager[27748
]: <info>  [1650959659.8483
] dhcp-init: Using DHCP client 'dhclient'
```
This log entry confirms that NetworkManager uses dhclient as DHCP client.

Additional resources

NetworkManager.conf(5) man page

2.16. Configuring the DHCP behavior of a NetworkManager connection

A Dynamic Host Configuration Protocol (DHCP) client requests the dynamic IP address and corresponding configuration information from a DHCP server each time a client connects to the network.

When you configured a connection to retrieve an IP address from a DHCP server, the NetworkManager requests an IP address from a DHCP server. By default, the client waits 45 seconds for this request to be completed. When a DHCP connection is started, a dhcp client requests an IP address from a DHCP server.

Prerequisites

A connection that uses DHCP is configured on the host.

Procedure

Set the ipv4.dhcp-timeout and ipv6.dhcp-timeout properties. For example, to set both options to 30 seconds, enter:
```
# nmcli connection modify 
connection_name
 ipv4.dhcp-timeout 30 ipv6.dhcp-timeout 30
```
Alternatively, set the parameters to infinity to configure that NetworkManager does not stop trying to request and renew an IP address until it is successful.
Optional: Configure the behavior if NetworkManager does not receive an IPv4 address before the timeout:
```
# nmcli connection modify 
connection_name
 ipv4.may-fail value
```
If you set the ipv4.may-fail option to:
- yes, the status of the connection depends on the IPv6 configuration:
  - If the IPv6 configuration is enabled and successful, NetworkManager activates the IPv6 connection and no longer tries to activate the IPv4 connection.
  - If the IPv6 configuration is disabled or not configured, the connection fails.
- no, the connection is deactivated. In this case:
  - If the autoconnect property of the connection is enabled, NetworkManager retries to activate the connection as many times as set in the autoconnect-retries property. The default is 4.
  - If the connection still cannot acquire a DHCP address, auto-activation fails. Note that after 5 minutes, the auto-connection process starts again to acquire an IP address from the DHCP server.
Optional: Configure the behavior if NetworkManager does not receive an IPv6 address before the timeout:
```
# nmcli connection modify 
connection_name
 ipv6.may-fail value
```

Additional resources

nm-settings(5) man page

2.17. Configuring multiple Ethernet interfaces using a single connection profile by interface name

In most cases, one connection profile contains the settings of one network device. However, NetworkManager also supports wildcards when you set the interface name in connection profiles. If a host roams between Ethernet networks with dynamic IP address assignment, you can use this feature to create a single connection profile that you can use for multiple Ethernet interfaces.

Prerequisites

Multiple physical or virtual Ethernet devices exist in the server’s configuration.
A DHCP server is available in the network.
No connection profile exists on the host.

Procedure

Add a connection profile that applies to all interface names starting with enp:

nmcli connection add con-name

Example

connection.multi-connect multiple match.interface-name enp* type ethernet

Verification steps

Display all settings of the single connection profile:
```
# nmcli connection show 
Example

connection.id:                      Example
...
connection.multi-connect:           3 (multiple)
match.interface-name:               enp*
...
```
3 indicates the number of interfaces active on the connection profile at the same time, and not the number of network interfaces in the connection profile. The connection profile uses all devices that match the pattern in the match.interface-name parameter and, therefore, the connection profiles have the same Universally Unique Identifier (UUID).

Display the status of the connections:

nmcli connection show

NAME UUID TYPE DEVICE ... Example 6f22402e-c0cc-49cf-b702-eaf0cd5ea7d1 ethernet enp7s0 Example 6f22402e-c0cc-49cf-b702-eaf0cd5ea7d1 ethernet enp8s0 Example 6f22402e-c0cc-49cf-b702-eaf0cd5ea7d1 ethernet enp9s0

Additional resources

nmcli(1) man page
nm-settings(5) man page

2.18. Configuring a single connection profile for multiple Ethernet interfaces using PCI IDs

The PCI ID is a unique identifier of the devices connected to the system. The connection profile adds multiple devices by matching interfaces based on a list of PCI IDs. You can use this procedure to connect multiple device PCI IDs to the single connection profile.

Prerequisites

Multiple physical or virtual Ethernet devices exist in the server’s configuration.
A DHCP server is available in the network.
No connection profile exists on the host.

Procedure

Identify the device path. For example, to display the device paths of all interfaces starting with enp, enter :

# udevadm info /sys/class/net/enp* | grep ID_PATH=
...
E: ID_PATH=pci-0000:07:00.0
E: ID_PATH=pci-0000:08:00.0

Add a connection profile that applies to all PCI IDs matching the 0000:00:0[7-8].0 expression:

nmcli connection add type ethernet connection.multi-connect multiple match.path "pci-0000:07:00.0 pci-0000:08:00.0" con-name

Example

Verification steps

Display the status of the connection:

nmcli connection show

NAME UUID TYPE DEVICE Example 9cee0958-512f-4203-9d3d-b57af1d88466 ethernet enp7s0 Example 9cee0958-512f-4203-9d3d-b57af1d88466 ethernet enp8s0 ...

To display all settings of the connection profile:
```
# nmcli connection show 
Example

connection.id:               Example
...
connection.multi-connect:    3 (multiple)
match.path:                  pci-0000:07:00.0,pci-0000:08:00.0
...
```
This connection profile uses all devices with a PCI ID which match the pattern in the match.path parameter and, therefore, the connection profiles have the same Universally Unique Identifier (UUID).

Additional resources

nmcli(1) man page
nm-settings(5) man page

Chapter 3. Managing wifi connections

RHEL provides multiple utilities and applications to configure and connect to wifi networks, for example:

The nmcli utility
The GNOME system menu
The GNOME Settings application
The nm-connection-editor application

3.1. Supported wifi security types

Depending on the security type a wifi network supports, you can transmitted data more or less securely.

Warning

Do not connect to wifi networks that do not use encryption or which support only the insecure WEP or WPA standards.

RHEL 8 supports the following wifi security types:

None: Encryption is disabled, and data is transferred in plain text over the network.
Enhanced Open: With opportunistic wireless encryption (OWE), devices negotiate unique pairwise master keys (PMK) to encrypt connections in wireless networks without authentication.
WEP 40/128-bit Key (Hex or ASCII): The Wired Equivalent Privacy (WEP) protocol in this mode uses pre-shared keys only in hex or ASCII format. WEP is deprecated and will be removed in RHEL 9.1.
WEP 128-bit Passphrase. The WEP protocol in this mode uses an MD5 hash of the passphrase to derive a WEP key. WEP is deprecated and will be removed in RHEL 9.1.
Dynamic WEP (802.1x): A combination of 802.1X and EAP that uses the WEP protocol with dynamic keys. WEP is deprecated and will be removed in RHEL 9.1.
LEAP: The Lightweight Extensible Authentication Protocol, which was developed by Cisco, is a proprietary version of the extensible authentication protocol (EAP).
WPA & WPA2 Personal: In personal mode, the Wi-Fi Protected Access (WPA) and Wi-Fi Protected Access 2 (WPA2) authentication methods use a pre-shared key.
WPA & WPA2 Enterprise: In enterprise mode, WPA and WPA2 use the EAP framework and authenticate users to a remote authentication dial-in user service (RADIUS) server.
WPA3 Personal: Wi-Fi Protected Access 3 (WPA3) Personal uses simultaneous authentication of equals (SAE) instead of pre-shared keys (PSK) to prevent dictionary attacks. WPA3 uses perfect forward secrecy (PFS).

3.2. Connecting to a WPA2 or WPA3 Personal-protected wifi network using nmcli commands

You can use the nmcli utility to connect to a wifi network. When you attempt to connect to a network for the first time, the utility automatically creates a NetworkManager connection profile for it. If the network requires additional settings, such as static IP addresses, you can then modify the profile after it has been automatically created.

Prerequisites

A wifi device is installed on the host.
The wifi device is enabled, if it has a hardware switch.

Procedure

If the wifi radio has been disabled in NetworkManager, enable this feature:
```
# nmcli radio wifi on
```

Optional: Display the available wifi networks:

nmcli device wifi list

IN-USE BSSID SSID MODE CHAN RATE SIGNAL BARS SECURITY 00:53:00:2F:3B:08 Office Infra 44 270 Mbit/s 57 ▂▄▆_ WPA2 WPA3 00:53:00:15:03:BF -- Infra 1 130 Mbit/s 48 ▂▄__ WPA2 WPA3

The service set identifier (SSID) column contains the names of the networks. If the column shows --, the access point of this network does not broadcast an SSID.

Connect to the wifi network:
```
# nmcli device wifi connect 
Office
 --ask
Password: 
wifi-password
```
If you prefer to set the password in the command instead of entering it interactively, use the password wifi-password option in the command instead of --ask:
```
# nmcli device wifi connect 
Office
 wifi-password
```
Note that, if the network requires static IP addresses, NetworkManager fails to activate the connection at this point. You can configure the IP addresses in later steps.

If the network requires static IP addresses:

Configure the IPv4 address settings, for example:

nmcli connection modify

Office

ipv4.method manual ipv4.addresses
192.0.2.1/24
ipv4.gateway
192.0.2.254
ipv4.dns
192.0.2.200
ipv4.dns-search
example.com

Configure the IPv6 address settings, for example:

nmcli connection modify

Office

ipv6.method manual ipv6.addresses
2001:db8:1::1/64
ipv6.gateway
2001:db8:1::fffe
ipv6.dns
2001:db8:1::ffbb
ipv6.dns-search
example.com

Re-activate the connection:
```
# nmcli connection up 
Office
```

Verification

Display the active connections:

nmcli connection show --active

NAME ID TYPE DEVICE

Office

2501eb7e-7b16-4dc6-97ef-7cc460139a58

wifi

wlp0s20f3

If the output lists the wifi connection you have created, the connection is active.

Ping a hostname or IP address:
```
# ping -c 3 
example.com
```

Additional resources

nm-settings-nmcli(5) man page

3.3. Configuring a wifi connection using nmtui

The nmtui application provides a text-based user interface for NetworkManager. You can use nmtui to connect to a wifi network.

Note

In nmtui:

Navigate by using the cursor keys.
Press a button by selecting it and hitting

Enter

.
Select and deselect checkboxes by using

Space

.

Procedure

If you do not know the network device name you want to use in the connection, display the available devices:

nmcli device status

DEVICE TYPE STATE CONNECTION

wlp2s0

wifi unavailable -- ...

Start nmtui:
```
# nmtui
```
Select Edit a connection, and press

Enter

.
Press the Add button.
Select Wi-Fi from the list of network types, and press

Enter

.
Optional: Enter a name for the NetworkManager profile to be created.
Enter the network device name into the Device field.
Enter the name of the Wi-Fi network, the Service Set Identifier (SSID), into the SSID field.
Leave the Mode field set to its default, Client.
Select the Security field, press Enter, and set the authentication type of the network from the list.

Depending on the authentication type you have selected, nmtui displays different fields.
Fill the authentication type-related fields.
If the Wi-Fi network requires static IP addresses:
1. Press the Automatic button next to the protocol, and select Manual from the displayed list.
2. Press the Show button next to the protocol you want to configure to display additional fields, and fill them.
Press the OK button to create and automatically activate the new connection.
Press the Back button to return to the main menu.
Select Quit, and press

Enter

to close the nmtui application.

Verification

Display the active connections:

nmcli connection show --active

NAME ID TYPE DEVICE

Office

2501eb7e-7b16-4dc6-97ef-7cc460139a58

wifi

wlp0s20f3

If the output lists the wifi connection you have created, the connection is active.

Ping a hostname or IP address:
```
# ping -c 3 
example.com
```

3.4. Connecting to a wifi network using the GNOME system menu

You can use the GNOME system menu to connect to a wifi network. When you connect to a network for the first time, GNOME creates a NetworkManager connection profile for it. If you configure the connection profile to not automatically connect, you can also use the GNOME system menu to manually connect to a wifi network with an existing NetworkManager connection profile.

Note

Using the GNOME system menu to establish a connection to a wifi network for the first time has certain limitations. For example, you can not configure IP address settings. In this case first configure the connections:

In the GNOME settings application
In the nm-connection-editor application
Using nmcli commands

Prerequisites

A wifi device is installed on the host.
The wifi device is enabled, if it has a hardware switch.

Procedure

Open the system menu on the right side of the top bar.
Expand the Wi-Fi Not Connected entry.
Click Select Network:
Select the wifi network you want to connect to.
Click Connect.
If this is the first time you connect to this network, enter the password for the network, and click Connect.

Verification

Open the system menu on the right side of the top bar, and verify that the wifi network is connected:

If the network appears in the list, it is connected.
Ping a hostname or IP address:
```
# ping -c 3 
example.com
```

3.5. Connecting to a wifi network using the GNOME settings application

You can use the GNOME settings application, also named gnome-control-center, to connect to a wifi network and configure the connection. When you connect to the network for the first time, GNOME creates a NetworkManager connection profile for it.

In GNOME settings, you can configure wifi connections for all wifi network security types that RHEL supports.

Prerequisites

A wifi device is installed on the host.
The wifi device is enabled, if it has a hardware switch.

Procedure

Press the

Super

key, type Wi-Fi, and press

Enter

.
Click on the name of the wifi network you want to connect to.
Enter the password for the network, and click Connect.
If the network requires additional settings, such as static IP addresses or a security type other than WPA2 Personal:
1. Click the gear icon next to the network’s name.
2. Optional: Configure the network profile on the Details tab to not automatically connect.
  
  If you deactivate this feature, you must always manually connect to the network, for example, using GNOME settings or the GNOME system menu.
3. Configure IPv4 settings on the IPv4 tab, and IPv6 settings on the IPv6 tab.
4. On the Security tab, select the authentication of the network, such as WPA3 Personal, and enter the password.
  
  Depending on the selected security, the application shows additional fields. Fill them accordingly. For details, ask the administrator of the wifi network.
5. Click Apply.

Verification

Open the system menu on the right side of the top bar, and verify that the wifi network is connected:

If the network appears in the list, it is connected.
Ping a hostname or IP address:
```
# ping -c 3 
example.com
```

3.6. Configuring a wifi connection using nm-connection-editor

You can use the nm-connection-editor application to create a connection profile for a wireless network. In this application you can configure all wifi network authentication types that RHEL supports.

By default, NetworkManager enables the auto-connect feature for connection profiles and automatically connects to a saved network if it is available.

Prerequisites

A wifi device is installed on the host.
The wifi device is enabled, if it has a hardware switch.

Procedure

Open a terminal and enter:
```
# nm-connection-editor
```
Click the

+

button to add a new connection.
Select the Wi-Fi connection type, and click

Create

.
Optional: Set a name for the connection profile.
Optional: Configure the network profile on the General tab to not automatically connect.

If you deactivate this feature, you must always manually connect to the network, for example, using GNOME settings or the GNOME system menu.
On the Wi-Fi tab, enter the service set identifier (SSID) in the SSID field.
On the Wi-Fi Security tab, select the authentication type for the network, such as WPA3 Personal, and enter the password.

Depending on the selected security, the application shows additional fields. Fill them accordingly. For details, ask the administrator of the wifi network.
Configure IPv4 settings on the IPv4 tab, and IPv6 settings on the IPv6 tab.
Click Save.
Close the Network Connections window.

Verification

Open the system menu on the right side of the top bar, and verify that the wifi network is connected:

If the network appears in the list, it is connected.
Ping a hostname or IP address:
```
# ping -c 3 
example.com
```

3.7. Configuring a wifi connection with 802.1X network authentication using the RHEL System Roles

Using RHEL System Roles, you can automate the creation of a wifi connection. For example, you can remotely add a wireless connection profile for the wlp1s0 interface using an Ansible playbook. The created profile uses the 802.1X standard to authenticate the client to a wifi network. The playbook configures the connection profile to use DHCP. To configure static IP settings, adapt the parameters in the ip dictionary accordingly.

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on them.
The hosts or host groups on which you want to run this playbook are listed in the Ansible inventory file.

The network supports 802.1X network authentication.
You installed the wpa_supplicant package on the managed node.
DHCP is available in the network of the managed node.
The following files required for TLS authentication exist on the control node:
- The client key is stored in the /srv/data/client.key file.
- The client certificate is stored in the /srv/data/client.crt file.
- The CA certificate is stored in the /srv/data/ca.crt file.

Procedure

Create a playbook file, for example ~/enable-802.1x.yml, with the following content:

--- - name:

Configure a wifi connection with 802.1X authentication

hosts: "

managed-node-01.example.com

" tasks: - name:

Copy client key for 802.1X authentication

copy: src: "

/srv/data/client.key

" dest: "

/etc/pki/tls/private/client.key

" mode: 0400 - name:

Copy client certificate for 802.1X authentication

copy: src: "

/srv/data/client.crt

" dest: "

/etc/pki/tls/certs/client.crt

" - name:

Copy CA certificate for 802.1X authentication

copy: src: "

/srv/data/ca.crt

" dest: "

/etc/pki/ca-trust/source/anchors/ca.crt

" - block: - import_role: name:

linux-system-roles.network

vars: network_connections: - name:

Configure the Example-wifi profile

interface_name:

wlp1s0

state: up type: wireless autoconnect:

yes

ip: dhcp4: true auto6: true wireless: ssid: "

Example-wifi

" key_mgmt: "

wpa-eap

" ieee802_1x: identity: "

user_name

" eap: tls private_key: "

/etc/pki/tls/client.key

" private_key_password: "

password

" private_key_password_flags: none client_cert: "

/etc/pki/tls/client.pem

" ca_cert: "

/etc/pki/tls/cacert.pem

" domain_suffix_match: "

example.com

Run the playbook:
```
# ansible-playbook 
~/enable-802.1x.yml
```

Additional resources

/usr/share/ansible/roles/rhel-system-roles.network/README.md file

3.8. Configuring 802.1X network authentication on an existing wifi connection using nmcli

Using the nmcli utility, you can configure the client to authenticate itself to the network. For example, you can configure Protected Extensible Authentication Protocol (PEAP) authentication with the Microsoft Challenge-Handshake Authentication Protocol version 2 (MSCHAPv2) in an existing NetworkManager wifi connection profile named wlp1s0.

Prerequisites

The network must have 802.1X network authentication.
The wifi connection profile exists in NetworkManager and has a valid IP configuration.
If the client is required to verify the certificate of the authenticator, the Certificate Authority (CA) certificate must be stored in the /etc/pki/ca-trust/source/anchors/ directory.
The wpa_supplicant package is installed.

Procedure

Set the wifi security mode to wpa-eap, the Extensible Authentication Protocol (EAP) to peap, the inner authentication protocol to mschapv2, and the user name:
```
# nmcli connection modify 
wlp1s0
 wireless-security.key-mgmt wpa-eap 802-1x.eap peap 802-1x.phase2-auth mschapv2 802-1x.identity user_name
```
Note that you must set the wireless-security.key-mgmt, 802-1x.eap, 802-1x.phase2-auth, and 802-1x.identity parameters in a single command.
Optionally, store the password in the configuration:
```
# nmcli connection modify 
wlp1s0
 802-1x.password password
```
Important

By default, NetworkManager stores the password in clear text in the /etc/sysconfig/network-scripts/keys-connection_name file, that is readable only by the root user. However, clear text passwords in a configuration file can be a security risk.

To increase the security, set the 802-1x.password-flags parameter to 0x1. With this setting, on servers with the GNOME desktop environment or the nm-applet running, NetworkManager retrieves the password from these services. In other cases, NetworkManager prompts for the password.
If the client is required to verify the certificate of the authenticator, set the 802-1x.ca-cert parameter in the connection profile to the path of the CA certificate:
```
# nmcli connection modify 
wlp1s0
 802-1x.ca-cert /etc/pki/ca-trust/source/anchors/ca.crt
```
Note

For security reasons, Red Hat recommends using the certificate of the authenticator to enable clients to validate the identity of the authenticator.
Activate the connection profile:
```
# nmcli connection up 
wlp1s0
```

Verification steps

Access resources on the network that require network authentication.

Additional resources

Managing wifi connections
nm-settings(5) man page
nmcli(1) man page

3.9. Manually setting the wireless regulatory domain

On RHEL, a udev rule executes the setregdomain utility to set the wireless regulatory domain. The utility then provides this information to the kernel.

By default, setregdomain attempts to determine the country code automatically. If this fails, the wireless regulatory domain setting might be wrong. To work around this problem, you can manually set the country code.

Important

Manually setting the regulatory domain disables the automatic detection. Therefore, if you later use the computer in a different country, the previously configured setting might no longer be correct. In this case, remove the /etc/sysconfig/regdomain file to switch back to automatic detection or use this procedure to manually update the regulatory domain setting again.

Procedure

Optional: Display the current regulatory domain settings:
```
# iw reg get
global
country US: DFS-FCC
...
```
Create the /etc/sysconfig/regdomain file with the following content:
```
COUNTRY=<country_code>
```
Set the COUNTRY variable to an ISO 3166-1 alpha2 country code, such as DE for Germany or US for the United States of America.
Set the regulatory domain:
```
# setregdomain
```

Verification

Display the regulatory domain settings:

iw reg get

global country

DE: DFS-ETSI

...

Additional resources

setregdomain(1) man page
iw(8) man page
regulatory.bin(5) man page
ISO 3166 Country Codes

Chapter 4. Configuring RHEL as a wifi access point

On a host with a wifi device, you can use NetworkManager to configure this host as an access point. Wireless clients can then use the access point to connect to services on the RHEL host or in the network.

When you configure an access point, NetworkManager automatically:

Configures the dnsmasq service to provide DHCP and DNS services for clients
Enables IP forwarding
Adds nftables firewall rules to masquerade traffic from the wifi device and configures IP forwarding

4.1. Identifying whether a wifi device supports the access point mode

To use a wifi device as an access point, the device must support this feature. You can use the nmcli utility to identify if the hardware supports access point mode.

Prerequisites

A wifi device is installed on the host.

Procedure

List the wifi devices to identify the one that should provide the access point:
```
# nmcli device status | grep wifi
wlp0s20f3
    wifi   disconnected    --
```

Verify that the device supports the access point mode:

nmcli -f WIFI-PROPERTIES.AP device show

wlp0s20f3

WIFI-PROPERTIES.AP: yes

4.2. Configuring RHEL as a WPA2 or WPA3 Personal access point

Wi-Fi Protected Access 2 (WPA2) and Wi-Fi Protected Access 3 (WPA3) Personal provide secure authentication methods in wireless networks. Users can connect to the access point using a pre-shared key (PSK).

Prerequisites

The wifi device supports running in access point mode.
The wifi device is not in use.
The host has internet access.

Procedure

Install the dnsmasq and NetworkManager-wifi packages:
```
# yum install dnsmasq NetworkManager-wifi
```
NetworkManager uses the dnsmasq service to provide DHCP and DNS services to clients of the access point.
Create the initial access point configuration:
```
# nmcli device wifi hotspot ifname 
wlp0s20f3
 con-name Example-Hotspot
 ssid Example-Hotspot
 password "password
"
```
This command creates a connection profile for an access point on the wlp0s20f3 device that provides WPA2 and WPA3 Personal authentication. The name of the wireless network, the Service Set Identifier (SSID), is Example-Hotspot and uses the pre-shared key password.

Optional: Configure the access point to support only WPA3:

nmcli connection modify

Example-Hotspot

802-11-wireless-security.key-mgmt sae

By default, NetworkManager uses the IP address 10.42.0.1 for the wifi device and assigns IP addresses from the remaining 10.42.0.0/24 subnet to clients. To configure a different subnet and IP address, enter:
```
# nmcli connection modify 
Example-Hotspot
 ipv4.addresses 192.0.2.254/24
```
The IP address you set, in this case 192.0.2.254, is the one that NetworkManager assigns to the wifi device. Clients will use this IP address as default gateway and DNS server.
Activate the connection profile:
```
# nmcli connection up 
Example-Hotspot
```

Verification

On the server:

Verify that NetworkManager started the dnsmasq service and that the service listens on port 67 (DHCP) and 53 (DNS):

# ss -tulpn | egrep ":53|:67"
udp   UNCONN 0  0   10.42.0.1
:53    0.0.0.0:*    users:(("dnsmasq",pid=55905
,fd=6))
udp   UNCONN 0  0     0.0.0.0:67    0.0.0.0:*    users:(("dnsmasq",pid=55905
,fd=4))
tcp   LISTEN 0  32  10.42.0.1
:53    0.0.0.0:*    users:(("dnsmasq",pid=55905
,fd=7
))

Display the nftables rule set to ensure that NetworkManager enabled forwarding and masquerading for traffic from the 10.42.0.0/24 subnet:

nft list ruleset

table ip nm-shared-wlp0s20f3 { chain nat_postrouting { type nat hook postrouting priority srcnat; policy accept; ip saddr

10.42.0.0/24

ip daddr !=

10.42.0.0/24

masquerade } chain filter_forward { type filter hook forward priority filter; policy accept; ip daddr

10.42.0.0/24

oifname "

wlp0s20f3

" ct state { established, related } accept ip saddr

10.42.0.0/24

iifname "

wlp0s20f3

" accept iifname "

wlp0s20f3

" oifname "

wlp0s20f3

" accept iifname "

wlp0s20f3

" reject oifname "

wlp0s20f3

" reject } }

On a client with a wifi adapter:

Display the list of available networks:

nmcli device wifi

IN-USE BSSID SSID MODE CHAN RATE SIGNAL BARS SECURITY

00:53:00:88:29:04

Example-Hotspot

Infra

130

Mbit/s

▂▄▆_

WPA3

...

Connect to the Example-Hotspot wireless network. See Managing Wi-Fi connections.
Ping a host on the remote network or the internet to verify that the connection works:
```
# ping -c 3 www.redhat.com
```

Additional resources

Identifying whether a wifi device supports the access point mode
nm-settings(5) man page

Chapter 5. Configuring VLAN tagging

A Virtual Local Area Network (VLAN) is a logical network within a physical network. The VLAN interface tags packets with the VLAN ID as they pass through the interface, and removes tags of returning packets. You create VLAN interfaces on top of another interface, such as Ethernet, bond, team, or bridge devices. These interfaces are called the parent interface.

Red Hat Enterprise Linux provides administrators different options to configure VLAN devices. For example:

Use nmcli to configure VLAN tagging using the command line.
Use the RHEL web console to configure VLAN tagging using a web browser.
Use nmtui to configure VLAN tagging in a text-based user interface.
Use the nm-connection-editor application to configure connections in a graphical interface.
Use nmstatectl to configure connections through the Nmstate API.
Use RHEL System Roles to automate the VLAN configuration on one or multiple hosts.

5.1. Configuring VLAN tagging using nmcli commands

You can configure Virtual Local Area Network (VLAN) tagging on the command line using the nmcli utility.

Prerequisites

The interface you plan to use as a parent to the virtual VLAN interface supports VLAN tags.
If you configure the VLAN on top of a bond interface:
- The ports of the bond are up.
- The bond is not configured with the fail_over_mac=follow option. A VLAN virtual device cannot change its MAC address to match the parent’s new MAC address. In such a case, the traffic would still be sent with the incorrect source MAC address.
- The bond is usually not expected to get IP addresses from a DHCP server or IPv6 auto-configuration. Ensure it by setting the ipv4.method=disable and ipv6.method=ignore options while creating the bond. Otherwise, if DHCP or IPv6 auto-configuration fails after some time, the interface might be brought down.
The switch, the host is connected to, is configured to support VLAN tags. For details, see the documentation of your switch.

Procedure

Display the network interfaces:

nmcli device status

DEVICE TYPE STATE CONNECTION enp1s0 ethernet disconnected enp1s0 bridge0 bridge connected bridge0 bond0 bond connected bond0 ...

Create the VLAN interface. For example, to create a VLAN interface named vlan10 that uses enp1s0 as its parent interface and that tags packets with VLAN ID 10, enter:
```
# nmcli connection add type vlan con-name 
vlan10
 ifname vlan10
 vlan.parent enp1s0
 vlan.id 10
```
Note that the VLAN must be within the range from 0 to 4094.
By default, the VLAN connection inherits the maximum transmission unit (MTU) from the parent interface. Optionally, set a different MTU value:
```
# nmcli connection modify vlan10 ethernet.mtu 
2000
```

Configure the IPv4 settings:

To use this VLAN device as a port of other devices, enter:
```
# nmcli connection modify vlan10 ipv4.method disabled
```
To use DHCP, no action is required.

To set a static IPv4 address, network mask, default gateway, and DNS server to the vlan10 connection, enter:

nmcli connection modify vlan10 ipv4.addresses '

192.0.2.1/24

nmcli connection modify vlan10 ipv4.gateway '

192.0.2.254

nmcli connection modify vlan10 ipv4.dns '

192.0.2.253

nmcli connection modify vlan10 ipv4.method manual

Configure the IPv6 settings:

To use this VLAN device as a port of other devices, enter:
```
# nmcli connection modify vlan10 ipv6.method disabled
```
To use DHCP, no action is required.

To set a static IPv6 address, network mask, default gateway, and DNS server to the vlan10 connection, enter:

nmcli connection modify vlan10 ipv6.addresses '

2001:db8:1::1/32

nmcli connection modify vlan10 ipv6.gateway '

2001:db8:1::fffe

nmcli connection modify vlan10 ipv6.dns '

2001:db8:1::fffd

nmcli connection modify vlan10 ipv6.method manual

Activate the connection:
```
# nmcli connection up vlan10
```

Verification steps

Verify the settings:

ip -d addr show

vlan10

4: vlan10@enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000 link/ether 52:54:00:72:2f:6e brd ff:ff:ff:ff:ff:ff promiscuity 0 vlan protocol 802.1Q id 10 <REORDER_HDR> numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 inet 192.0.2.1/24 brd 192.0.2.255 scope global noprefixroute vlan10 valid_lft forever preferred_lft forever inet6 2001:db8:1::1/32 scope global noprefixroute valid_lft forever preferred_lft forever inet6 fe80::8dd7:9030:6f8e:89e6/64 scope link noprefixroute valid_lft forever preferred_lft forever

Additional resources

Configuring NetworkManager to avoid using a specific profile to provide a default gateway
nm-settings(5) man page

5.2. Configuring VLAN tagging using the RHEL web console

Use the RHEL web console to configure VLAN tagging if you prefer to manage network settings using a web browser-based interface.

Prerequisites

The interface you plan to use as a parent to the virtual VLAN interface supports VLAN tags.
If you configure the VLAN on top of a bond interface:
- The ports of the bond are up.
- The bond is not configured with the fail_over_mac=follow option. A VLAN virtual device cannot change its MAC address to match the parent’s new MAC address. In such a case, the traffic would still be sent with the incorrect source MAC address.
- The bond is usually not expected to get IP addresses from a DHCP server or IPv6 auto-configuration. Ensure it by disabling the IPv4 and IPv6 protocol creating the bond. Otherwise, if DHCP or IPv6 auto-configuration fails after some time, the interface might be brought down.
The switch, the host is connected to, is configured to support VLAN tags. For details, see the documentation of your switch.

Procedure

Select the Networking tab in the navigation on the left side of the screen.
Click

Add VLAN

in the Interfaces section.
Select the parent device.
Enter the VLAN ID.
Enter the name of the VLAN device or keep the automatically-generated name.
Click

Apply

.
By default, the VLAN device uses a dynamic IP address. If you want to set a static IP address:
1. Click the name of the VLAN device in the Interfaces section.
2. Click Edit next to the protocol you want to configure.
3. Select Manual next to Addresses, and enter the IP address, prefix, and default gateway.
4. In the DNS section, click the
  
  +
  
  button, and enter the IP address of the DNS server. Repeat this step to set multiple DNS servers.
5. In the DNS search domains section, click the
  
  +
  
  button, and enter the search domain.
6. If the interface requires static routes, configure them in the Routes section.
7. Click
  
  Apply

Verification

Select the Networking tab in the navigation on the left side of the screen, and check if there is incoming and outgoing traffic on the interface:

5.3. Configuring VLAN tagging using nmtui

The nmtui application provides a text-based user interface for NetworkManager. You can use nmtui to configure VLAN tagging on a host without a graphical interface.

Note

In nmtui:

Navigate by using the cursor keys.
Press a button by selecting it and hitting

Enter

.
Select and deselect checkboxes by using

Space

.

Prerequisites

The interface you plan to use as a parent to the virtual VLAN interface supports VLAN tags.
If you configure the VLAN on top of a bond interface:
- The ports of the bond are up.
- The bond is not configured with the fail_over_mac=follow option. A VLAN virtual device cannot change its MAC address to match the parent’s new MAC address. In such a case, the traffic would still be sent with the then incorrect source MAC address.
- The bond is usually not expected to get IP addresses from a DHCP server or IPv6 auto-configuration. Ensure it by setting the ipv4.method=disable and ipv6.method=ignore options while creating the bond. Otherwise, if DHCP or IPv6 auto-configuration fails after some time, the interface might be brought down.
The switch the host is connected to is configured to support VLAN tags. For details, see the documentation of your switch.

Procedure

If you do not know the network device name on which you want configure VLAN tagging, display the available devices:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp1s0

ethernet unavailable -- ...

Start nmtui:
```
# nmtui
```
Select Edit a connection, and press

Enter

.
Press the Add button.
Select VLAN from the list of network types, and press

Enter

.
Optional: Enter a name for the NetworkManager profile to be created.
Enter the VLAN device name to be created into the Device field.
Enter the name of the device on which you want to configure VLAN tagging into the Parent field.
Enter the VLAN ID. The ID must be within the range from 0 to 4094.
Depending on your environment, configure the IP address settings in the IPv4 configuration and IPv6 configuration areas accordingly. For this, press the Automatic button, and select:
- Disabled, if this VLAN device does not require an IP address or you want to use it as a port of other devices.
- Automatic, if a DHCP server dynamically assigns an IP address to the VLAN device.
- Manual, if the network requires static IP address settings. In this case, you must fill further fields:
  1. Press the Show button next to the protocol you want to configure to display additional fields.
  2. Press the Add button next to Addresses, and enter the IP address and the subnet mask in Classless Inter-Domain Routing (CIDR) format.
    
    If you do not specify a subnet mask, NetworkManager sets a /32 subnet mask for IPv4 addresses and /64 for IPv6 addresses.
  3. Enter the address of the default gateway.
  4. Press the Add button next to DNS servers, and enter the DNS server address.
  5. Press the Add button next to Search domains, and enter the DNS search domain.
Figure 5.1. Example of a VLAN connection with static IP address settings
Press the OK button to create and automatically activate the new connection.
Press the Back button to return to the main menu.
Select Quit, and press

Enter

to close the nmtui application.

Verification

Verify the settings:

ip -d addr show

vlan10

5.4. Configuring VLAN tagging using nm-connection-editor

You can configure Virtual Local Area Network (VLAN) tagging in a graphical interface using the nm-connection-editor application.

Prerequisites

The interface you plan to use as a parent to the virtual VLAN interface supports VLAN tags.
If you configure the VLAN on top of a bond interface:
- The ports of the bond are up.
- The bond is not configured with the fail_over_mac=follow option. A VLAN virtual device cannot change its MAC address to match the parent’s new MAC address. In such a case, the traffic would still be sent with the incorrect source MAC address.
The switch, the host is connected, to is configured to support VLAN tags. For details, see the documentation of your switch.

Procedure

Open a terminal, and enter nm-connection-editor:
```
$ nm-connection-editor
```
Click the

+

button to add a new connection.
Select the VLAN connection type, and click

Create

.
On the VLAN tab:
1. Select the parent interface.
2. Select the VLAN id. Note that the VLAN must be within the range from 0 to 4094.
3. By default, the VLAN connection inherits the maximum transmission unit (MTU) from the parent interface. Optionally, set a different MTU value.
4. Optionally, set the name of the VLAN interface and further VLAN-specific options.
Configure the IP settings of the VLAN device. Skip this step if you want to use this VLAN device as a port of other devices.
1. On the IPv4 Settings tab, configure the IPv4 settings. For example, set a static IPv4 address, network mask, default gateway, and DNS server:
2. On the IPv6 Settings tab, configure the IPv6 settings. For example, set a static IPv6 address, network mask, default gateway, and DNS server:
Click

Save

to save the VLAN connection.
Close nm-connection-editor.

Verification steps

Verify the settings:

ip -d addr show

vlan10

4: vlan10@enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000 link/ether 52:54:00:d5:e0:fb brd ff:ff:ff:ff:ff:ff promiscuity 0 vlan protocol 802.1Q id 10 <REORDER_HDR> numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 inet 192.0.2.1/24 brd 192.0.2.255 scope global noprefixroute vlan10 valid_lft forever preferred_lft forever inet6 2001:db8:1::1/32 scope global noprefixroute valid_lft forever preferred_lft forever inet6 fe80::8dd7:9030:6f8e:89e6/64 scope link noprefixroute valid_lft forever preferred_lft forever

Additional resources

Configuring NetworkManager to avoid using a specific profile to provide a default gateway

5.5. Configuring VLAN tagging using nmstatectl

You can use the nmstatectl utility to configure Virtual Local Area Network (VLAN) tagging. This example configures a VLAN with ID 10 that uses an Ethernet connection. As the child device, the VLAN connection contains the IP, default gateway, and DNS configurations.

Depending on your environment, adjust the YAML file accordingly. For example, to use a bridge, or bond device in the VLAN, adapt the base-iface attribute and type attributes of the ports you use in the VLAN.

Prerequisites

To use Ethernet devices as ports in the VLAN, the physical or virtual Ethernet devices must be installed on the server.
The nmstate package is installed.

Procedure

Create a YAML file, for example ~/create-vlan.yml, with the following contents:

---
interfaces:
- name: vlan10
  type: vlan
  state: up
  ipv4:
    enabled: true
    address:
    - ip: 192.0.2.1
      prefix-length: 24
    dhcp: false
  ipv6:
    enabled: true
    address:
    - ip: 2001:db8:1::1
      prefix-length: 64
    autoconf: false
    dhcp: false
  vlan:
    base-iface: enp1s0
    id: 10
- name: enp1s0
  type: ethernet
  state: up

routes:
  config:
  - destination: 0.0.0.0/0
    next-hop-address: 192.0.2.254
    next-hop-interface: vlan10
  - destination: ::/0
    next-hop-address: 2001:db8:1::fffe
    next-hop-interface: vlan10

dns-resolver:
  config:
    search:
    - example.com
    server:
    - 192.0.2.200
    - 2001:db8:1::ffbb

Apply the settings to the system:
```
# nmstatectl apply ~/create-vlan.yml
```

Verification steps

Display the status of the devices and connections:

nmcli device status

DEVICE TYPE STATE CONNECTION

vlan10

vlan

connected

vlan10

Display all settings of the connection profile:

nmcli connection show

vlan10

connection.id:

vlan10

connection.uuid:

1722970f-788e-4f81-bd7d-a86bf21c9df5

connection.stable-id: -- connection.type: vlan connection.interface-name:

vlan10

...

Display the connection settings in YAML format:
```
# nmstatectl show 
vlan0
```

Additional resources

nmstatectl(8) man page
/usr/share/doc/nmstate/examples/ directory

5.6. Configuring VLAN tagging using RHEL System Roles

You can use the network RHEL System Role to configure VLAN tagging. This example adds an Ethernet connection and a VLAN with ID 10 on top of this Ethernet connection. As the child device, the VLAN connection contains the IP, default gateway, and DNS configurations.

Depending on your environment, adjust the play accordingly. For example:

To use the VLAN as a port in other connections, such as a bond, omit the ip attribute, and set the IP configuration in the child configuration.
To use team, bridge, or bond devices in the VLAN, adapt the interface_name and type attributes of the ports you use in the VLAN.

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on them.
The hosts or host groups on which you to want run this playbook are listed in the Ansible inventory file.

Procedure

Create a playbook file, for example ~/vlan-ethernet.yml, with the following content:

--- - name: Configure the network hosts:

managed-node-01.example.com

tasks: - name: Configure a VLAN that uses an Ethernet connection include_role: name: rhel-system-roles.network vars: network_connections: # Add an Ethernet profile for the underlying device of the VLAN - name: enp1s0 type: ethernet interface_name: enp1s0 autoconnect: yes state: up ip: dhcp4: no auto6: no # Define the VLAN profile - name: enp1s0.10 type: vlan ip: address: - "192.0.2.1/24" - "2001:db8:1::1/64" gateway4: 192.0.2.254 gateway6: 2001:db8:1::fffe dns: - 192.0.2.200 - 2001:db8:1::ffbb dns_search: - example.com vlan_id: 10 parent: enp1s0 state: up

The parent attribute in the VLAN profile configures the VLAN to operate on top of the enp1s0 device.

Run the playbook:
```
# ansible-playbook 
~/vlan-ethernet.yml
```

Additional resources

/usr/share/ansible/roles/rhel-system-roles.network/README.md file

5.7. Additional resources

VLANs for sysadmins: The basics

Chapter 6. Using a VXLAN to create a virtual layer-2 domain for VMs

A virtual extensible LAN (VXLAN) is a networking protocol that tunnels layer-2 traffic over an IP network using the UDP protocol. For example, certain virtual machines (VMs), that are running on different hosts can communicate over a VXLAN tunnel. The hosts can be in different subnets or even in different data centers around the world. From the perspective of the VMs, other VMs in the same VXLAN are within the same layer-2 domain:

vxlan tunnel

In this example, RHEL-host-A and RHEL-host-B use a bridge, br0, to connect the virtual network of a VM on each host with a VXLAN named vxlan10. Due to this configuration, the VXLAN is invisible to the VMs, and the VMs do not require any special configuration. If you later connect more VMs to the same virtual network, the VMs are automatically members of the same virtual layer-2 domain.

Important

Just as normal layer-2 traffic, data in a VXLAN is not encrypted. For security reasons, use a VXLAN over a VPN or other types of encrypted connections.

6.1. Benefits of VXLANs

A virtual extensible LAN (VXLAN) provides the following major benefits:

VXLANs use a 24-bit ID. Therefore, you can create up to 16,777,216 isolated networks. For example, a virtual LAN (VLAN), supports only 4,096 isolated networks.
VXLANs use the IP protocol. This enables you to route the traffic and virtually run systems in different networks and locations within the same layer-2 domain.
Unlike most tunnel protocols, a VXLAN is not only a point-to-point network. A VXLAN can learn the IP addresses of the other endpoints either dynamically or use statically-configured forwarding entries.
Certain network cards support UDP tunnel-related offload features.

Additional resources

/usr/share/doc/kernel-doc- <kernel_version>
/Documentation/networking/vxlan.rst provided by the kernel-doc package

6.2. Configuring the Ethernet interface on the hosts

To connect a RHEL VM host to the Ethernet, create a network connection profile, configure the IP settings, and activate the profile.

Run this procedure on both RHEL hosts, and adjust the IP address configuration accordingly.

Prerequisites

The host is connected to the Ethernet.

Procedure

Add a new Ethernet connection profile to NetworkManager:

nmcli connection add con-name

Example

ifname
enp1s0
type ethernet

Configure the IPv4 settings:

nmcli connection modify

Example

ipv4.addresses
198.51.100.2/24
ipv4.method manual ipv4.gateway
198.51.100.254
ipv4.dns
198.51.100.200
ipv4.dns-search
example.com

Skip this step if the network uses DHCP.

Activate the Example connection:
```
# nmcli connection up 
Example
```

Verification

Display the status of the devices and connections:

nmcli device status

DEVICE TYPE STATE CONNECTION enp1s0 ethernet connected

Example

Ping a host in a remote network to verify the IP settings:
```
# ping 
RHEL-host-B.example.com
```
Note that you cannot ping the other VM host before you have configured the network on that host as well.

Additional resources

nm-settings(5) man page

6.3. Creating a network bridge with a VXLAN attached

To make a virtual extensible LAN (VXLAN) invisible to virtual machines (VMs), create a bridge on a host, and attach the VXLAN to the bridge. Use NetworkManager to create both the bridge and the VXLAN. You do not add any traffic access point (TAP) devices of the VMs, typically named vnet* on the host, to the bridge. The libvirtd service adds them dynamically when the VMs start.

Run this procedure on both RHEL hosts, and adjust the IP addresses accordingly.

Procedure

Create the bridge br0:
```
# nmcli connection add type bridge con-name br0 ifname br0 ipv4.method disabled ipv6.method disabled
```
This command sets no IPv4 and IPv6 addresses on the bridge device, because this bridge works on layer 2.
Create the VXLAN interface and attach it to br0:
```
# nmcli connection add type vxlan slave-type bridge con-name 
br0-vxlan10
 ifname vxlan10
 id 10
 local 198.51.100.2
 remote 203.0.113.1
 master br0
```
This command uses the following settings:
- id 10: Sets the VXLAN identifier.
- local 198.51.100.2: Sets the source IP address of outgoing packets.
- remote 203.0.113.1: Sets the unicast or multicast IP address to use in outgoing packets when the destination link layer address is not known in the VXLAN device forwarding database.
- master br0: Sets this VXLAN connection to be created as a port in the br0 connection.
- ipv4.method disabled and ipv6.method disabled: Disables IPv4 and IPv6 on the bridge.
By default, NetworkManager uses 8472 as the destination port. If the destination port is different, additionally, pass the destination-port <port_number> option to the command.
Activate the br0 connection profile:
```
# nmcli connection up 
br0
```

Open port 8472 for incoming UDP connections in the local firewall:

firewall-cmd --permanent --add-port=8472/udp

firewall-cmd --reload

Verification

Display the forwarding table:

bridge fdb show dev

vxlan10

2a:53:bd:d5:b3:0a master br0 permanent 00:00:00:00:00:00 dst 203.0.113.1 self permanent ...

Additional resources

nm-settings(5) man page

6.4. Creating a virtual network in libvirt with an existing bridge

To enable virtual machines (VM) to use the br0 bridge with the attached virtual extensible LAN (VXLAN), first add a virtual network to the libvirtd service that uses this bridge.

Prerequisites

You installed the libvirt package.
You started and enabled the libvirtd service.
You configured the br0 device with the VXLAN on RHEL.

Procedure

Create the ~/vxlan10-bridge.xml file with the following content:

<network>
 <name>vxlan10-bridge</name>
 <forward mode="bridge" />
 <bridge name="br0" />
</network>

Use the ~/vxlan10-bridge.xml file to create a new virtual network in libvirt:
```
# virsh net-define 
~/vxlan10-bridge.xml
```
Remove the ~/vxlan10-bridge.xml file:
```
# rm 
~/vxlan10-bridge.xml
```
Start the vxlan10-bridge virtual network:
```
# virsh net-start 
vxlan10-bridge
```
Configure the vxlan10-bridge virtual network to start automatically when the libvirtd service starts:
```
# virsh net-autostart 
vxlan10-bridge
```

Verification

Display the list of virtual networks:

virsh net-list

Name State Autostart Persistent ----------------------------------------------------

vxlan10-bridge

active yes yes ...

Additional resources

virsh(1) man page

6.5. Configuring virtual machines to use VXLAN

To configure a VM to use a bridge device with an attached virtual extensible LAN (VXLAN) on the host, create a new VM that uses the vxlan10-bridge virtual network or update the settings of existing VMs to use this network.

Perform this procedure on the RHEL hosts.

Prerequisites

You configured the vxlan10-bridge virtual network in libvirtd.

Procedure

To create a new VM and configure it to use the vxlan10-bridge network, pass the --network network:vxlan10-bridge option to the virt-install command when you create the VM:
```
# virt-install ... --network network:
vxlan10-bridge
```
To change the network settings of an existing VM:
1. Connect the VM’s network interface to the vxlan10-bridge virtual network:
```
# virt-xml 
VM_name
 --edit --network network=vxlan10-bridge
```
2. Shut down the VM, and start it again:
```
# virsh shutdown 
VM_name

# virsh start 
VM_name
```

Verification

Display the virtual network interfaces of the VM on the host:

virsh domiflist

VM_name

Interface Type Source Model MAC -------------------------------------------------------------------

vnet1

bridge

vxlan10-bridge

virtio

52:54:00:c5:98:1c

Display the interfaces attached to the vxlan10-bridge bridge:

ip link show master vxlan10-bridge

18: vxlan10: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master

br0

state UNKNOWN mode DEFAULT group default qlen 1000 link/ether

2a:53:bd:d5:b3:0a

brd ff:ff:ff:ff:ff:ff 19: vnet1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master

br0

state UNKNOWN mode DEFAULT group default qlen 1000 link/ether

52:54:00:c5:98:1c

brd ff:ff:ff:ff:ff:ff

Note that the libvirtd service dynamically updates the bridge’s configuration. When you start a VM which uses the vxlan10-bridge network, the corresponding vnet* device on the host appears as a port of the bridge.

Use address resolution protocol (ARP) requests to verify whether VMs are in the same VXLAN:
1. Start two or more VMs in the same VXLAN.
2. Send an ARP request from one VM to the other one:
```
# arping -c 1 
192.0.2.2

ARPING 192.0.2.2
 from 192.0.2.1
 enp1s0
Unicast reply from 192.0.2.2
 [52:54:00:c5:98:1c
] 1.450ms
Sent 1 probe(s) (0 broadcast(s))
Received 1 response(s) (0 request(s), 0 broadcast(s))
```
  If the command shows a reply, the VM is in the same layer-2 domain and, in this case in the same VXLAN.
  
  Install the iputils package to use the arping utility.

Additional resources

virt-install(1) man page
virt-xml(1) man page
virsh(1) man page
arping(8) man page

Chapter 7. Configuring a network bridge

A network bridge is a link-layer device which forwards traffic between networks based on a table of MAC addresses. The bridge builds the MAC addresses table by listening to network traffic and thereby learning what hosts are connected to each network. For example, you can use a software bridge on a Red Hat Enterprise Linux host to emulate a hardware bridge or in virtualization environments, to integrate virtual machines (VM) to the same network as the host.

A bridge requires a network device in each network the bridge should connect. When you configure a bridge, the bridge is called controller and the devices it uses ports.

You can create bridges on different types of devices, such as:

Physical and virtual Ethernet devices
Network bonds
Network teams
VLAN devices

Due to the IEEE 802.11 standard which specifies the use of 3-address frames in Wi-Fi for the efficient use of airtime, you cannot configure a bridge over Wi-Fi networks operating in Ad-Hoc or Infrastructure modes.

7.1. Configuring a network bridge using nmcli commands

To configure a network bridge on the command line, use the nmcli utility.

Prerequisites

Two or more physical or virtual network devices are installed on the server.
To use Ethernet devices as ports of the bridge, the physical or virtual Ethernet devices must be installed on the server.
To use team, bond, or VLAN devices as ports of the bridge, you can either create these devices while you create the bridge or you can create them in advance as described in:
- Configuring a network team using nmcli commands
- Configuring a network bond using nmcli commands
- Configuring VLAN tagging using nmcli commands

Procedure

Create a bridge interface:
```
# nmcli connection add type bridge con-name 
bridge0
 ifname bridge0
```
This command creates a bridge named bridge0, enter:
Display the network interfaces, and note the names of the interfaces you want to add to the bridge:
```
# nmcli device status
DEVICE  TYPE      STATE         CONNECTION
enp7s0  ethernet  disconnected  --
enp8s0  ethernet  disconnected  --
bond0   bond      connected     bond0
bond1   bond      connected     bond1
...
```
In this example:
- enp7s0 and enp8s0 are not configured. To use these devices as ports, add connection profiles in the next step.
- bond0 and bond1 have existing connection profiles. To use these devices as ports, modify their profiles in the next step.
Assign the interfaces to the bridge.
1. If the interfaces you want to assign to the bridge are not configured, create new connection profiles for them:
```
# nmcli connection add type ethernet slave-type bridge con-name 
bridge0-port1
 ifname enp7s0 master bridge0
# nmcli connection add type ethernet slave-type bridge con-name 
bridge0-port2
 ifname enp8s0 master bridge0
```
  These commands create profiles for enp7s0 and enp8s0, and add them to the bridge0 connection.
2. If you want to assign an existing connection profile to the bridge:
  1. Set the master parameter of these connections to bridge0:
```
# nmcli connection modify 
bond0
 master bridge0
# nmcli connection modify 
bond1
 master bridge0
```
    These commands assign the existing connection profiles named bond0 and bond1 to the bridge0 connection.
  2. Reactivate the connections:
```
# nmcli connection up 
bond0

# nmcli connection up 
bond1
```

Configure the IPv4 settings:

To use this bridge device as a port of other devices, enter:
```
# nmcli connection modify bridge0 ipv4.method disabled
```
To use DHCP, no action is required.

To set a static IPv4 address, network mask, default gateway, and DNS server to the bridge0 connection, enter:

nmcli connection modify bridge0 ipv4.addresses '

192.0.2.1/24

nmcli connection modify bridge0 ipv4.gateway '

192.0.2.254

nmcli connection modify bridge0 ipv4.dns '

192.0.2.253

nmcli connection modify bridge0 ipv4.dns-search '

example.com

nmcli connection modify bridge0 ipv4.method manual

Configure the IPv6 settings:

To use this bridge device as a port of other devices, enter:
```
# nmcli connection modify bridge0 ipv6.method disabled
```
To use DHCP, no action is required.

To set a static IPv6 address, network mask, default gateway, and DNS server to the bridge0 connection, enter:

nmcli connection modify bridge0 ipv6.addresses '

2001:db8:1::1/64

nmcli connection modify bridge0 ipv6.gateway '

2001:db8:1::fffe

nmcli connection modify bridge0 ipv6.dns '

2001:db8:1::fffd

nmcli connection modify bridge0 ipv6.dns-search '

example.com

nmcli connection modify bridge0 ipv6.method manual

Optional: Configure further properties of the bridge. For example, to set the Spanning Tree Protocol (STP) priority of bridge0 to 16384, enter:
```
# nmcli connection modify bridge0 bridge.priority '16384'
```
By default, STP is enabled.
Activate the connection:
```
# nmcli connection up bridge0
```
Verify that the ports are connected, and the CONNECTION column displays the port’s connection name:
```
# nmcli device
DEVICE   TYPE      STATE      CONNECTION
...
enp7s0   ethernet  connected  bridge0-port1
enp8s0   ethernet  connected  bridge0-port2
```
When you activate any port of the connection, NetworkManager also activates the bridge, but not the other ports of it. You can configure that Red Hat Enterprise Linux enables all ports automatically when the bridge is enabled:
1. Enable the connection.autoconnect-slaves parameter of the bridge connection:
```
# nmcli connection modify bridge0 connection.autoconnect-slaves 1
```
2. Reactivate the bridge:
```
# nmcli connection up bridge0
```

Verification steps

Use the ip utility to display the link status of Ethernet devices that are ports of a specific bridge:

ip link show master

bridge0

3: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UP mode DEFAULT group default qlen 1000 link/ether 52:54:00:62:61:0e brd ff:ff:ff:ff:ff:ff 4: enp8s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UP mode DEFAULT group default qlen 1000 link/ether 52:54:00:9e:f1:ce brd ff:ff:ff:ff:ff:ff

Use the bridge utility to display the status of Ethernet devices that are ports of any bridge device:

bridge link show

3: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state forwarding priority 32 cost 100 4: enp8s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state listening priority 32 cost 100 5: enp9s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge1 state forwarding priority 32 cost 100 6: enp11s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge1 state blocking priority 32 cost 100 ...

To display the status for a specific Ethernet device, use the bridge link show dev ethernet_device_name command.

Additional resources

Configuring NetworkManager to avoid using a specific profile to provide a default gateway
nm-settings(5) man page
bridge(8) man page
NetworkManager duplicates a connection after restart of NetworkManager service
How to configure bridge with vlan information?

7.2. Configuring a network bridge using the RHEL web console

Use the RHEL web console to configure a network bridge if you prefer to manage network settings using a web browser-based interface.

Prerequisites

Two or more physical or virtual network devices are installed on the server.
To use Ethernet devices as ports of the bridge, the physical or virtual Ethernet devices must be installed on the server.
To use team, bond, or VLAN devices as ports of the bridge, you can either create these devices while you create the bridge or you can create them in advance as described in:
- Configuring a network team using the RHEL web console
- Configuring a network bond using the RHEL web console
- Configuring VLAN tagging using the RHEL web console

Procedure

Select the Networking tab in the navigation on the left side of the screen.
Click

Add bridge

in the Interfaces section.
Enter the name of the bridge device you want to create.
Select the interfaces that should be ports of the bridge.
Optional: Enable the Spanning tree protocol (STP) feature to avoid bridge loops and broadcast radiation.
Click

Apply

.
By default, the bridge uses a dynamic IP address. If you want to set a static IP address:
1. Click the name of the bridge in the Interfaces section.
2. Click Edit next to the protocol you want to configure.
3. Select Manual next to Addresses, and enter the IP address, prefix, and default gateway.
4. In the DNS section, click the
  
  +
  
  button, and enter the IP address of the DNS server. Repeat this step to set multiple DNS servers.
5. In the DNS search domains section, click the
  
  +
  
  button, and enter the search domain.
6. If the interface requires static routes, configure them in the Routes section.
7. Click
  
  Apply

Verification

Select the Networking tab in the navigation on the left side of the screen, and check if there is incoming and outgoing traffic on the interface:

7.3. Configuring a network bridge using nmtui

The nmtui application provides a text-based user interface for NetworkManager. You can use nmtui to configure a network bridge on a host without a graphical interface.

Note

In nmtui:

Navigate by using the cursor keys.
Press a button by selecting it and hitting

Enter

.
Select and deselect checkboxes by using

Space

.

Prerequisites

Two or more physical or virtual network devices are installed on the server.
To use Ethernet devices as ports of the bridge, the physical or virtual Ethernet devices must be installed on the server.

Procedure

If you do not know the network device names on which you want configure a network bridge, display the available devices:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp7s0

ethernet unavailable --

enp8s0

ethernet unavailable -- ...

Start nmtui:
```
# nmtui
```
Select Edit a connection, and press

Enter

.
Press the Add button.
Select Bridge from the list of network types, and press

Enter

.
Optional: Enter a name for the NetworkManager profile to be created.
Enter the bridge device name to be created into the Device field.
Add ports to the bridge to be created:
1. Press the Add button next to the Slaves list.
2. Select the type of the interface you want to add as port to the bridge, for example, Ethernet.
3. Optional: Enter a name for the NetworkManager profile to be created for this bridge port.
4. Enter the port’s device name into the Device field.
5. Press the OK button to return to the window with the bridge settings.
  
  Figure 7.1. Adding an Ethernet device as port to a bridge
6. Repeat these steps to add more ports to the bridge.
Depending on your environment, configure the IP address settings in the IPv4 configuration and IPv6 configuration areas accordingly. For this, press the Automatic button, and select:
- Disabled, if the bridge does not require an IP address.
- Automatic, if a DHCP server dynamically assigns an IP address to the bridge.
- Manual, if the network requires static IP address settings. In this case, you must fill further fields:
  1. Press the Show button next to the protocol you want to configure to display additional fields.
  2. Press the Add button next to Addresses, and enter the IP address and the subnet mask in Classless Inter-Domain Routing (CIDR) format.
    
    If you do not specify a subnet mask, NetworkManager sets a /32 subnet mask for IPv4 addresses and /64 for IPv6 addresses.
  3. Enter the address of the default gateway.
  4. Press the Add button next to DNS servers, and enter the DNS server address.
  5. Press the Add button next to Search domains, and enter the DNS search domain.
Figure 7.2. Example of a bridge connection without IP address settings
Press the OK button to create and automatically activate the new connection.
Press the Back button to return to the main menu.
Select Quit, and press

Enter

to close the nmtui application.

Verification

Use the ip utility to display the link status of Ethernet devices that are ports of a specific bridge:

ip link show master

bridge0

Use the bridge utility to display the status of Ethernet devices that are ports of any bridge device:

bridge link show

To display the status for a specific Ethernet device, use the bridge link show dev ethernet_device_name command.

7.4. Configuring a network bridge using nm-connection-editor

If you use Red Hat Enterprise Linux with a graphical interface, you can configure network bridges using the nm-connection-editor application.

Note that nm-connection-editor can add only new ports to a bridge. To use an existing connection profile as a port, create the bridge using the nmcli utility as described in Configuring a network bridge using nmcli commands.

Prerequisites

Two or more physical or virtual network devices are installed on the server.
To use Ethernet devices as ports of the bridge, the physical or virtual Ethernet devices must be installed on the server.
To use team, bond, or VLAN devices as ports of the bridge, ensure that these devices are not already configured.

Procedure

Open a terminal, and enter nm-connection-editor:
```
$ nm-connection-editor
```
Click the

+

button to add a new connection.
Select the Bridge connection type, and click

Create

.
In the Bridge tab:
1. Optional: Set the name of the bridge interface in the Interface name field.
2. Click the Add button to create a new connection profile for a network interface and adding the profile as a port to the bridge.
  1. Select the connection type of the interface. For example, select Ethernet for a wired connection.
  2. Optionally, set a connection name for the port device.
  3. If you create a connection profile for an Ethernet device, open the Ethernet tab, and select in the Device field the network interface you want to add as a port to the bridge. If you selected a different device type, configure it accordingly.
  4. Click
    
    Save
    
    .
3. Repeat the previous step for each interface you want to add to the bridge.
Optional: Configure further bridge settings, such as Spanning Tree Protocol (STP) options.
Configure the IP settings of the bridge. Skip this step if you want to use this bridge as a port of other devices.
1. In the IPv4 Settings tab, configure the IPv4 settings. For example, set a static IPv4 address, network mask, default gateway, DNS server, and DNS search domain:
2. In the IPv6 Settings tab, configure the IPv6 settings. For example, set a static IPv6 address, network mask, default gateway, DNS server, and DNS search domain:
Save the bridge connection.
Close nm-connection-editor.

Verification steps

Use the ip utility to display the link status of Ethernet devices that are ports of a specific bridge.

ip link show master

bridge0

Use the bridge utility to display the status of Ethernet devices that are ports in any bridge device:

bridge link show

To display the status for a specific Ethernet device, use the bridge link show dev ethernet_device_name command.

Additional resources

Configuring a network bond using nm-connection-editor
Configuring a network team using nm-connection-editor
Configuring VLAN tagging using nm-connection-editor
Configuring NetworkManager to avoid using a specific profile to provide a default gateway
How to configure bridge with vlan information?

7.5. Configuring a network bridge using nmstatectl

To configure a network bridge using the Nmstate API, use the nmstatectl utility.

For example, the procedure below creates a bridge in NetworkManager with the following settings:

Network interfaces in the bridge: enp1s0 and enp7s0
Spanning Tree Protocol (STP): Enabled
Static IPv4 address: 192.0.2.1 with the /24 subnet mask
Static IPv6 address: 2001:db8:1::1 with the /64 subnet mask
IPv4 default gateway: 192.0.2.254
IPv6 default gateway: 2001:db8:1::fffe
IPv4 DNS server: 192.0.2.200
IPv6 DNS server: 2001:db8:1::ffbb
DNS search domain: example.com

Prerequisites

Two or more physical or virtual network devices are installed on the server.
To use Ethernet devices as ports in the bridge, the physical or virtual Ethernet devices must be installed on the server.
To use team, bond, or VLAN devices as ports in the bridge, set the interface name in the port list, and define the corresponding interfaces.
The nmstate package is installed.

Procedure

Create a YAML file, for example ~/create-bridge.yml, with the following contents:

---
interfaces:
- name: bridge0
  type: linux-bridge
  state: up
  ipv4:
    enabled: true
    address:
    - ip: 192.0.2.1
      prefix-length: 24
    dhcp: false
  ipv6:
    enabled: true
    address:
    - ip: 2001:db8:1::1
      prefix-length: 64
    autoconf: false
    dhcp: false
  bridge:
    options:
      stp:
        enabled: true
    port:
      - name: enp1s0
      - name: enp7s0
- name: enp1s0
  type: ethernet
  state: up
- name: enp7s0
  type: ethernet
  state: up

routes:
  config:
  - destination: 0.0.0.0/0
    next-hop-address: 192.0.2.254
    next-hop-interface: bridge0
  - destination: ::/0
    next-hop-address: 2001:db8:1::fffe
    next-hop-interface: bridge0
dns-resolver:
  config:
    search:
    - example.com
    server:
    - 192.0.2.200
    - 2001:db8:1::ffbb

Apply the settings to the system:
```
# nmstatectl apply ~/create-bridge.yml
```

Verification steps

Display the status of the devices and connections:

nmcli device status

DEVICE TYPE STATE CONNECTION

bridge0

bridge

connected

bridge0

Display all settings of the connection profile:

nmcli connection show

bridge0

connection.id:

bridge0

connection.uuid:

e2cc9206-75a2-4622-89cf-1252926060a9

connection.stable-id: -- connection.type: bridge connection.interface-name:

bridge0

...

Display the connection settings in YAML format:
```
# nmstatectl show 
bridge0
```

Additional resources

nmstatectl(8) man page
/usr/share/doc/nmstate/examples/ directory
How to configure bridge with vlan information?

7.6. Configuring a network bridge using RHEL System Roles

You can use the network RHEL System Role to configure a Linux bridge. For example, use it to configure a network bridge that uses two Ethernet devices, and sets IPv4 and IPv6 addresses, default gateways, and DNS configuration.

Note

Set the IP configuration on the bridge and not on the ports of the Linux bridge.

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on them.
The hosts or host groups on which you want to run this playbook are listed in the Ansible inventory file.

Two or more physical or virtual network devices are installed on the server.

Procedure

Create a playbook file, for example ~/bridge-ethernet.yml, with the following content:

--- - name: Configure the network hosts:

managed-node-01.example.com

tasks: - name: Configure a network bridge that uses two Ethernet ports include_role: name: rhel-system-roles.network vars: network_connections: # Define the bridge profile - name: bridge0 type: bridge interface_name: bridge0 ip: address: - "192.0.2.1/24" - "2001:db8:1::1/64" gateway4: 192.0.2.254 gateway6: 2001:db8:1::fffe dns: - 192.0.2.200 - 2001:db8:1::ffbb dns_search: - example.com state: up # Add an Ethernet profile to the bridge - name: bridge0-port1 interface_name: enp7s0 type: ethernet controller: bridge0 port_type: bridge state: up # Add a second Ethernet profile to the bridge - name: bridge0-port2 interface_name: enp8s0 type: ethernet controller: bridge0 port_type: bridge state: up

Run the playbook:

ansible-playbook

~/bridge-ethernet.yml

Additional resources

/usr/share/ansible/roles/rhel-system-roles.network/README.md file

Chapter 9. Configuring network bonding

A network bond is a method to combine or aggregate physical and virtual network interfaces to provide a logical interface with higher throughput or redundancy. In a bond, the kernel handles all operations exclusively. You can create bonds on different types of devices, such as Ethernet devices or VLANs.

Red Hat Enterprise Linux provides administrators different options to configure team devices. For example:

Use nmcli to configure bond connections using the command line.
Use the RHEL web console to configure bond connections using a web browser.
Use nmtui to configure bond connections in a text-based user interface.
Use the nm-connection-editor application to configure bond connections in a graphical interface.
Use nmstatectl to configure bond connections through the Nmstate API.
Use RHEL System Roles to automate the bond configuration on one or multiple hosts.

9.1. Understanding network bonding

Network bonding is a method to combine or aggregate network interfaces to provide a logical interface with higher throughput or redundancy.

The active-backup, balance-tlb, and balance-alb modes do not require any specific configuration of the network switch. However, other bonding modes require configuring the switch to aggregate the links. For example, Cisco switches requires EtherChannel for modes 0, 2, and 3, but for mode 4, the Link Aggregation Control Protocol (LACP) and EtherChannel are required.

For further details, see the documentation of your switch and Linux Ethernet Bonding Driver HOWTO.

Important

Certain network bonding features, such as the fail-over mechanism, do not support direct cable connections without a network switch. For further details, see the Is bonding supported with direct connection using crossover cables? KCS solution.

9.2. Understanding the default behavior of controller and port interfaces

Consider the following default behavior of, when managing or troubleshooting team or bond port interfaces using the NetworkManager service:

Starting the controller interface does not automatically start the port interfaces.
Starting a port interface always starts the controller interface.
Stopping the controller interface also stops the port interface.
A controller without ports can start static IP connections.
A controller without ports waits for ports when starting DHCP connections.
A controller with a DHCP connection waiting for ports completes when you add a port with a carrier.
A controller with a DHCP connection waiting for ports continues waiting when you add a port without carrier.

9.3. Comparison of network teaming and bonding features

Learn about the features supported in network teams and network bonds:

FeatureNetwork bondNetwork team

Broadcast Tx policy

Yes

Round-robin Tx policy

Yes

Active-backup Tx policy

Yes

LACP (802.3ad) support

Yes (active only)

Yes

Hash-based Tx policy

Yes

User can set hash function

Yes

Tx load-balancing support (TLB)

Yes

LACP hash port select

Yes

Load-balancing for LACP support

Yes

Ethtool link monitoring

Yes

ARP link monitoring

Yes

NS/NA (IPv6) link monitoring

Yes

Ports up/down delays

Yes

Port priorities and stickiness (“primary” option enhancement)

Yes

Separate per-port link monitoring setup

Yes

Multiple link monitoring setup

Limited

Yes

Lockless Tx/Rx path

No (rwlock)

Yes (RCU)

VLAN support

Yes

User-space runtime control

Limited

Yes

Logic in user-space

Yes

Extensibility

Hard

Easy

Modular design

Yes

Performance overhead

Low

Very low

D-Bus interface

Yes

Multiple device stacking

Yes

Zero config using LLDP

(in planning)

NetworkManager support

Yes

9.4. Upstream Switch Configuration Depending on the Bonding Modes

Apply the following settings to the upstream switch depending on the bonding mode:

Bonding modeConfiguration on the switch

0 – balance-rr

Requires static Etherchannel enabled (not LACP-negotiated)

1 – active-backup

Requires autonomous ports

2 – balance-xor

Requires static Etherchannel enabled (not LACP-negotiated)

3 – broadcast

Requires static Etherchannel enabled (not LACP-negotiated)

4 – 802.3ad

Requires LACP-negotiated Etherchannel enabled

5 – balance-tlb

Requires autonomous ports

6 – balance-alb

Requires autonomous ports

For configuring these settings on your switch, see the documentation of the switch.

9.5. Configuring a network bond using nmcli commands

To configure a network bond on the command line, use the nmcli utility.

Prerequisites

Two or more physical or virtual network devices are installed on the server.
To use Ethernet devices as ports of the bond, the physical or virtual Ethernet devices must be installed on the server.
To use team, bridge, or VLAN devices as ports of the bond, you can either create these devices while you create the bond or you can create them in advance as described in:
- Configuring a network team using nmcli commands
- Configuring a network bridge using nmcli commands
- Configuring VLAN tagging using nmcli commands

Procedure

Create a bond interface:
```
# nmcli connection add type bond con-name 
bond0
 ifname bond0
 bond.options "mode=active-backup
"
```
This command creates a bond named bond0 that uses the active-backup mode.

To additionally set a Media Independent Interface (MII) monitoring interval, add the miimon=interval option to the bond.options property. For example, to use the same command but, additionally, set the MII monitoring interval to 1000 milliseconds (1 second), enter:
```
# nmcli connection add type bond con-name bond0 ifname bond0 bond.options "mode=
active-backup
,miimon=1000
"
```
Display the network interfaces, and note names of interfaces you plan to add to the bond:
```
# nmcli device status
DEVICE   TYPE      STATE         CONNECTION
enp7s0   ethernet  disconnected  --
enp8s0   ethernet  disconnected  --
bridge0  bridge    connected     bridge0
bridge1  bridge    connected     bridge1
...
```
In this example:
- enp7s0 and enp8s0 are not configured. To use these devices as ports, add connection profiles in the next step.
- bridge0 and bridge1 have existing connection profiles. To use these devices as ports, modify their profiles in the next step.

Assign interfaces to the bond:

If the interfaces you want to assign to the bond are not configured, create new connection profiles for them:

nmcli connection add type ethernet slave-type bond con-name

bond0-port1

ifname
enp7s0
master bond0

nmcli connection add type ethernet slave-type bond con-name

bond0-port2

ifname
enp8s0
master bond0

These commands create profiles for enp7s0 and enp8s0, and add them to the bond0 connection.

To assign an existing connection profile to the bond:
1. Set the master parameter of these connections to bond0:
```
# nmcli connection modify 
bridge0
 master bond0
# nmcli connection modify 
bridge1
 master bond0
```
  These commands assign the existing connection profiles named bridge0 and bridge1 to the bond0 connection.
2. Reactivate the connections:
```
# nmcli connection up 
bridge0

# nmcli connection up 
bridge1
```

Configure the IPv4 settings:

To use this bond device as a port of other devices, enter:
```
# nmcli connection modify bond0 ipv4.method disabled
```
To use DHCP, no action is required.

To set a static IPv4 address, network mask, default gateway, and DNS server to the bond0 connection, enter:

nmcli connection modify bond0 ipv4.addresses '

192.0.2.1/24

nmcli connection modify bond0 ipv4.gateway '

192.0.2.254

nmcli connection modify bond0 ipv4.dns '

192.0.2.253

nmcli connection modify bond0 ipv4.dns-search '

example.com

nmcli connection modify bond0 ipv4.method manual

Configure the IPv6 settings:

To use this bond device as a port of other devices, enter:
```
# nmcli connection modify bond0 ipv6.method disabled
```
To use DHCP, no action is required.

To set a static IPv6 address, network mask, default gateway, and DNS server to the bond0 connection, enter:

nmcli connection modify bond0 ipv6.addresses '

2001:db8:1::1/64

nmcli connection modify bond0 ipv6.gateway '

2001:db8:1::fffe

nmcli connection modify bond0 ipv6.dns '

2001:db8:1::fffd

nmcli connection modify bond0 ipv6.dns-search '

example.com

nmcli connection modify bond0 ipv6.method manual

Activate the connection:
```
# nmcli connection up bond0
```
Verify that the ports are connected, and the CONNECTION column displays the port’s connection name:
```
# nmcli device
DEVICE   TYPE      STATE      CONNECTION
...
enp7s0   ethernet  connected  bond0-port1
enp8s0   ethernet  connected  bond0-port2
```
When you activate any port of the connection, NetworkManager also activates the bond, but not the other ports of it. You can configure that Red Hat Enterprise Linux enables all ports automatically when the bond is enabled:
1. Enable the connection.autoconnect-slaves parameter of the bond’s connection:
```
# nmcli connection modify bond0 connection.autoconnect-slaves 1
```
2. Reactivate the bridge:
```
# nmcli connection up bond0
```

Verification steps

Temporarily remove the network cable from the host.

Note that there is no method to properly test link failure events using software utilities. Tools that deactivate connections, such as nmcli, show only the bonding driver’s ability to handle port configuration changes and not actual link failure events.
Display the status of the bond:
```
# cat /proc/net/bonding/
bond0
```

Additional resources

Configuring NetworkManager to avoid using a specific profile to provide a default gateway
Network bonding documentation

9.6. Configuring a network bond using the RHEL web console

Use the RHEL web console to configure a network bond if you prefer to manage network settings using a web browser-based interface.

Prerequisites

You are logged in to the RHEL web console.
Two or more physical or virtual network devices are installed on the server.
To use Ethernet devices as members of the bond, the physical or virtual Ethernet devices must be installed on the server.
To use team, bridge, or VLAN devices as members of the bond, create them in advance as described in:
- Configuring a network team using the RHEL web console
- Configuring a network bridge using the RHEL web console
- Configuring VLAN tagging using the RHEL web console

Procedure

Select the Networking tab in the navigation on the left side of the screen.
Click

Add bond

in the Interfaces section.
Enter the name of the bond device you want to create.
Select the interfaces that should be members of the bond.
Select the mode of the bond.

If you select Active backup, the web console shows the additional field Primary in which you can select the preferred active device.
Set the link monitoring mode. For example, when you use the Adaptive load balancing mode, set it to ARP.
Optional: Adjust the monitoring interval, link up delay, and link down delay settings. Typically, you only change the defaults for troubleshooting purposes.
Click

Apply

.
By default, the bond uses a dynamic IP address. If you want to set a static IP address:
1. Click the name of the bond in the Interfaces section.
2. Click Edit next to the protocol you want to configure.
3. Select Manual next to Addresses, and enter the IP address, prefix, and default gateway.
4. In the DNS section, click the
  
  +
  
  button, and enter the IP address of the DNS server. Repeat this step to set multiple DNS servers.
5. In the DNS search domains section, click the
  
  +
  
  button, and enter the search domain.
6. If the interface requires static routes, configure them in the Routes section.
7. Click
  
  Apply

Verification

Select the Networking tab in the navigation on the left side of the screen, and check if there is incoming and outgoing traffic on the interface:
Temporarily remove the network cable from the host.

Note that there is no method to properly test link failure events using software utilities. Tools that deactivate connections, such as the web console, show only the bonding driver’s ability to handle member configuration changes and not actual link failure events.
Display the status of the bond:
```
# cat /proc/net/bonding/
bond0
```

9.7. Configuring a network bond using nmtui

The nmtui application provides a text-based user interface for NetworkManager. You can use nmtui to configure a network bond on a host without a graphical interface.

Note

In nmtui:

Navigate by using the cursor keys.
Press a button by selecting it and hitting

Enter

.
Select and deselect checkboxes by using

Space

.

Prerequisites

Two or more physical or virtual network devices are installed on the server.
To use Ethernet devices as ports of the bond, the physical or virtual Ethernet devices must be installed on the server.

Procedure

If you do not know the network device names on which you want configure a network bond, display the available devices:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp7s0

ethernet unavailable --

enp8s0

ethernet unavailable -- ...

Start nmtui:
```
# nmtui
```
Select Edit a connection, and press

Enter

.
Press the Add button.
Select Bond from the list of network types, and press

Enter

.
Optional: Enter a name for the NetworkManager profile to be created.
Enter the bond device name to be created into the Device field.
Add ports to the bond to be created:
1. Press the Add button next to the Slaves list.
2. Select the type of the interface you want to add as port to the bond, for example, Ethernet.
3. Optional: Enter a name for the NetworkManager profile to be created for this bond port.
4. Enter the port’s device name into the Device field.
5. Press the OK button to return to the window with the bond settings.
  
  Figure 9.1. Adding an Ethernet device as port to a bond
6. Repeat these steps to add more ports to the bond.
Set the bond mode. Depending on the value you set, nmtui displays additional fields for settings that are related to the selected mode.
Depending on your environment, configure the IP address settings in the IPv4 configuration and IPv6 configuration areas accordingly. For this, press the Automatic button, and select:
- Disabled, if the bond does not require an IP address.
- Automatic, if a DHCP server dynamically assigns an IP address to the bond.
- Manual, if the network requires static IP address settings. In this case, you must fill further fields:
  1. Press the Show button next to the protocol you want to configure to display additional fields.
  2. Press the Add button next to Addresses, and enter the IP address and the subnet mask in Classless Inter-Domain Routing (CIDR) format.
    
    If you do not specify a subnet mask, NetworkManager sets a /32 subnet mask for IPv4 addresses and /64 for IPv6 addresses.
  3. Enter the address of the default gateway.
  4. Press the Add button next to DNS servers, and enter the DNS server address.
  5. Press the Add button next to Search domains, and enter the DNS search domain.
Figure 9.2. Example of a bond connection with static IP address settings
Press the OK button to create and automatically activate the new connection.
Press the Back button to return to the main menu.
Select Quit, and press

Enter

to close the nmtui application.

Verification

Temporarily remove the network cable from the host.

Note that there is no method to properly test link failure events using software utilities. Tools that deactivate connections, such as nmcli, show only the bonding driver’s ability to handle port configuration changes and not actual link failure events.
Display the status of the bond:
```
# cat /proc/net/bonding/
bond0
```

9.8. Configuring a network bond using nm-connection-editor

If you use Red Hat Enterprise Linux with a graphical interface, you can configure network bonds using the nm-connection-editor application.

Note that nm-connection-editor can add only new ports to a bond. To use an existing connection profile as a port, create the bond using the nmcli utility as described in Configuring a network bond using nmcli commands.

Prerequisites

Two or more physical or virtual network devices are installed on the server.
To use Ethernet devices as ports of the bond, the physical or virtual Ethernet devices must be installed on the server.
To use team, bond, or VLAN devices as ports of the bond, ensure that these devices are not already configured.

Procedure

Open a terminal, and enter nm-connection-editor:
```
$ nm-connection-editor
```
Click the

+

button to add a new connection.
Select the Bond connection type, and click

Create

.
In the Bond tab:
1. Optional: Set the name of the bond interface in the Interface name field.
2. Click the Add button to add a network interface as a port to the bond.
  1. Select the connection type of the interface. For example, select Ethernet for a wired connection.
  2. Optional: Set a connection name for the port.
  3. If you create a connection profile for an Ethernet device, open the Ethernet tab, and select in the Device field the network interface you want to add as a port to the bond. If you selected a different device type, configure it accordingly. Note that you can only use Ethernet interfaces in a bond that are not configured.
  4. Click
    
    Save
    
    .
3. Repeat the previous step for each interface you want to add to the bond:
4. Optional: Set other options, such as the Media Independent Interface (MII) monitoring interval.
Configure the IP settings of the bond. Skip this step if you want to use this bond as a port of other devices.
1. In the IPv4 Settings tab, configure the IPv4 settings. For example, set a static IPv4 address, network mask, default gateway, DNS server, and DNS search domain:
2. In the IPv6 Settings tab, configure the IPv6 settings. For example, set a static IPv6 address, network mask, default gateway, DNS server, and DNS search domain:
Click

Save

to save the bond connection.
Close nm-connection-editor.

Verification steps

Temporarily remove the network cable from the host.

Note that there is no method to properly test link failure events using software utilities. Tools that deactivate connections, such as nmcli, show only the bonding driver’s ability to handle port configuration changes and not actual link failure events.
Display the status of the bond:
```
# cat /proc/net/bonding/
bond0
```

Additional resources

Configuring NetworkManager to avoid using a specific profile to provide a default gateway
Configuring a network team using nm-connection-editor
Configuring a network bridge using nm-connection-editor
Configuring VLAN tagging using nm-connection-editor

9.9. Configuring a network bond using nmstatectl

To configure a network bond using the Nmstate API, use the nmstatectl utility.

For example, the procedure below creates a bond in NetworkManager with the following settings:

Network interfaces in the bond: enp1s0 and enp7s0
Mode: active-backup
Static IPv4 address: 192.0.2.1 with a /24 subnet mask
Static IPv6 address: 2001:db8:1::1 with a /64 subnet mask
IPv4 default gateway: 192.0.2.254
IPv6 default gateway: 2001:db8:1::fffe
IPv4 DNS server: 192.0.2.200
IPv6 DNS server: 2001:db8:1::ffbb
DNS search domain: example.com

Prerequisites

Two or more physical or virtual network devices are installed on the server.
To use Ethernet devices as ports in the bond, the physical or virtual Ethernet devices must be installed on the server.
To use team, bridge, or VLAN devices as ports in the bond, set the interface name in the port list, and define the corresponding interfaces.
The nmstate package is installed.

Procedure

Create a YAML file, for example ~/create-bond.yml, with the following contents:

---
interfaces:
- name: bond0
  type: bond
  state: up
  ipv4:
    enabled: true
    address:
    - ip: 192.0.2.1
      prefix-length: 24
    dhcp: false
  ipv6:
    enabled: true
    address:
    - ip: 2001:db8:1::1
      prefix-length: 64
    autoconf: false
    dhcp: false
  link-aggregation:
    mode: active-backup
    port:
    - enp1s0
    - enp7s0
- name: enp1s0
  type: ethernet
  state: up
- name: enp7s0
  type: ethernet
  state: up

routes:
  config:
  - destination: 0.0.0.0/0
    next-hop-address: 192.0.2.254
    next-hop-interface: bond0
  - destination: ::/0
    next-hop-address: 2001:db8:1::fffe
    next-hop-interface: bond0

dns-resolver:
  config:
    search:
    - example.com
    server:
    - 192.0.2.200
    - 2001:db8:1::ffbb

Apply the settings to the system:
```
# nmstatectl apply ~/create-bond.yml
```

Verification steps

Display the status of the devices and connections:

nmcli device status

DEVICE TYPE STATE CONNECTION

bond0

bond

connected

bond0

Display all settings of the connection profile:

nmcli connection show

bond0

connection.id:

bond0

connection.uuid:

79cbc3bd-302e-4b1f-ad89-f12533b818ee

connection.stable-id: -- connection.type: bond connection.interface-name:

bond0

...

Display the connection settings in YAML format:
```
# nmstatectl show 
bond0
```

Additional resources

nmstatectl(8) man page
/usr/share/doc/nmstate/examples/ directory

9.10. Configuring a network bond using RHEL System Roles

You can use the network RHEL System Roles to configure a Linux bond. For example, use it to configure a network bond in active-backup mode that uses two Ethernet devices, and sets an IPv4 and IPv6 addresses, default gateways, and DNS configuration.

Note

Set the IP configuration on the bond and not on the ports of the Linux bond.

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on them.
The hosts or host groups on which you want to run this playbook are listed in the Ansible inventory file.

Two or more physical or virtual network devices are installed on the server.

Procedure

Create a playbook file, for example ~/bond-ethernet.yml, with the following content:

--- - name: Configure the network hosts:

managed-node-01.example.com

tasks: name: Configure a network bond that uses two Ethernet ports - include_role: name: rhel-system-roles.network vars: network_connections: # Define the bond profile - name: bond0 type: bond interface_name: bond0 ip: address: - "192.0.2.1/24" - "2001:db8:1::1/64" gateway4: 192.0.2.254 gateway6: 2001:db8:1::fffe dns: - 192.0.2.200 - 2001:db8:1::ffbb dns_search: - example.com bond: mode: active-backup state: up # Add an Ethernet profile to the bond - name: bond0-port1 interface_name: enp7s0 type: ethernet controller: bond0 state: up # Add a second Ethernet profile to the bond - name: bond0-port2 interface_name: enp8s0 type: ethernet controller: bond0 state: up

Run the playbook:
```
# ansible-playbook 
~/bond-ethernet.yml
```

Additional resources

/usr/share/ansible/roles/rhel-system-roles.network/README.md file

9.11. Creating a network bond to enable switching between an Ethernet and wireless connection without interrupting the VPN

RHEL users who connect their workstation to their company’s network typically use a VPN to access remote resources. However, if the workstation switches between an Ethernet and Wi-Fi connection, for example, if you release a laptop from a docking station with an Ethernet connection, the VPN connection is interrupted. To avoid this problem, you can create a network bond that uses the Ethernet and Wi-Fi connection in active-backup mode.

Prerequisites

The host contains an Ethernet and a Wi-Fi device.
An Ethernet and Wi-Fi NetworkManager connection profile has been created and both connections work independently.

This procedure uses the following connection profiles to create a network bond named bond0:
- Docking_station associated with the enp11s0u1 Ethernet device
- Wi-Fi associated with the wlp1s0 Wi-Fi device

Procedure

Create a bond interface in active-backup mode:
```
# nmcli connection add type bond con-name bond0 ifname bond0 bond.options "mode=active-backup"
```
This command names both the interface and connection profile bond0.

Configure the IPv4 settings of the bond:

If a DHCP server in your network assigns IPv4 addresses to hosts, no action is required.

If your local network requires static IPv4 addresses, set the address, network mask, default gateway, DNS server, and DNS search domain to the bond0 connection:

nmcli connection modify bond0 ipv4.addresses '

192.0.2.1/24

nmcli connection modify bond0 ipv4.gateway '

192.0.2.254

nmcli connection modify bond0 ipv4.dns '

192.0.2.253

nmcli connection modify bond0 ipv4.dns-search '

example.com

nmcli connection modify bond0 ipv4.method manual

Configure the IPv6 settings of the bond:

If your router or a DHCP server in your network assigns IPv6 addresses to hosts, no action is required.

If your local network requires static IPv6 addresses, set the address, network mask, default gateway, DNS server, and DNS search domain to the bond0 connection:

nmcli connection modify bond0 ipv6.addresses '

2001:db8:1::1/64

nmcli connection modify bond0 ipv6.gateway '

2001:db8:1::fffe

nmcli connection modify bond0 ipv6.dns '

2001:db8:1::fffd

nmcli connection modify bond0 ipv6.dns-search '

example.com

nmcli connection modify bond0 ipv6.method manual

Display the connection profiles:

nmcli connection show

NAME UUID TYPE DEVICE Docking_station 256dd073-fecc-339d-91ae-9834a00407f9 ethernet enp11s0u1 Wi-Fi 1f1531c7-8737-4c60-91af-2d21164417e8 wifi wlp1s0 ...

You require the names of the connection profiles and the Ethernet device name in the next steps.

Assign the connection profile of the Ethernet connection to the bond:
```
# nmcli connection modify 
Docking_station
 master bond0
```
Assign the connection profile of the Wi-Fi connection to the bond:
```
# nmcli connection modify 
Wi-Fi
 master bond0
```
If your Wi-Fi network uses MAC filtering to allow only MAC addresses on a allow list to access the network, configure that NetworkManager dynamically assigns the MAC address of the active port to the bond:
```
# nmcli connection modify bond0 +bond.options fail_over_mac=1
```
With this setting, you must set only the MAC address of the Wi-Fi device to the allow list instead of the MAC address of both the Ethernet and Wi-Fi device.
Set the device associated with the Ethernet connection as primary device of the bond:
```
# nmcli con modify bond0 +bond.options "primary=enp11s0u1"
```
With this setting, the bond always uses the Ethernet connection if it is available.
Configure that NetworkManager automatically activates ports when the bond0 device is activated:
```
# nmcli connection modify bond0 connection.autoconnect-slaves 1
```
Activate the bond0 connection:
```
# nmcli connection up bond0
```

Verification steps

Display the currently active device, the status of the bond and its ports:

cat /proc/net/bonding/bond0

Ethernet Channel Bonding Driver: v3.7.1 (April 27, 2011) Bonding Mode: fault-tolerance (active-backup) (fail_over_mac active) Primary Slave: enp11s0u1 (primary_reselect always)

Currently Active Slave: enp11s0u1

MII Status: up

MII Polling Interval (ms): 1 Up Delay (ms): 0 Down Delay (ms): 0 Peer Notification Delay (ms): 0 Slave Interface: enp11s0u1

MII Status: up

Speed: 1000 Mbps Duplex: full Link Failure Count: 0 Permanent HW addr: 00:53:00:59:da:b7 Slave queue ID: 0 Slave Interface: wlp1s0

MII Status: up

Speed: Unknown Duplex: Unknown Link Failure Count: 2 Permanent HW addr: 00:53:00:b3:22:ba Slave queue ID: 0

Additional resources

Configuring an Ethernet connection
Managing Wi-Fi connections
Configuring network bonding

9.12. The different network bonding modes

The Linux bonding driver provides link aggregation. Bonding is the process of aggregating multiple network interfaces in parallel to provide a single logical bonded interface. The actions of a bonded interface depend on the bonding policy that is also known as mode. The different modes provide either load-balancing or hot standby services.

The following modes exist:

Balance-rr (Mode 0)

Balance-rr uses the round-robin algorithm that sequentially transmits packets from the first available port to the last one. This mode provides load balancing and fault tolerance.

This mode requires switch configuration of a port aggregation group, also called EtherChannel or similar port grouping. An EtherChannel is a port link aggregation technology to group multiple physical Ethernet links to one logical Ethernet link.

The drawback of this mode is that it is not suitable for heavy workloads and if TCP throughput or ordered packet delivery is essential.

Active-backup (Mode 1)

Active-backup uses the policy that determines that only one port is active in the bond. This mode provides fault tolerance and does not require any switch configuration.

If the active port fails, an alternate port becomes active. The bond sends a gratuitous address resolution protocol (ARP) response to the network. The gratuitous ARP forces the receiver of the ARP frame to update their forwarding table. The Active-backup mode transmits a gratuitous ARP to announce the new path to maintain connectivity for the host.

The primary option defines the preferred port of the bonding interface.

Balance-xor (Mode 2)

Balance-xor uses the selected transmit hash policy to send the packets. This mode provides load balancing, fault tolerance, and requires switch configuration to set up an Etherchannel or similar port grouping.

To alter packet transmission and balance transmit, this mode uses the xmit_hash_policy option. Depending on the source or destination of traffic on the interface, the interface requires an additional load-balancing configuration. See description xmit_hash_policy bonding parameter.

Broadcast (Mode 3)

Broadcast uses a policy that transmits every packet on all interfaces. This mode provides fault tolerance and requires a switch configuration to set up an EtherChannel or similar port grouping.

The drawback of this mode is that it is not suitable for heavy workloads and if TCP throughput or ordered packet delivery is essential.

802.3ad (Mode 4)

802.3ad uses the same-named IEEE standard dynamic link aggregation policy. This mode provides fault tolerance. This mode requires switch configuration to set up a Link Aggregation Control Protocol (LACP) port grouping.

This mode creates aggregation groups that share the same speed and duplex settings and utilizes all ports in the active aggregator. Depending on the source or destination of traffic on the interface, this mode requires an additional load-balancing configuration.

By default, the port selection for outgoing traffic depends on the transmit hash policy. Use the xmit_hash_policy option of the transmit hash policy to change the port selection and balance transmit.

The difference between the 802.3ad and the Balance-xor is compliance. The 802.3ad policy negotiates LACP between the port aggregation groups. See description xmit_hash_policy bonding parameter

Balance-tlb (Mode 5)

Balance-tlb uses the transmit load balancing policy. This mode provides fault tolerance, load balancing, and establishes channel bonding that does not require any switch support.

The active port receives the incoming traffic. In case of failure of the active port, another one takes over the MAC address of the failed port. To decide which interface processes the outgoing traffic, use one of the following modes:

Value 0: Uses the hash distribution policy to distribute traffic without load balancing
Value 1: Distributes traffic to each port by using load balancing

With the bonding option tlb_dynamic_lb=0, this bonding mode uses the xmit_hash_policy bonding option to balance transmit. The primary option defines the preferred port of the bonding interface.

See description xmit_hash_policy bonding parameter.

Balance-alb (Mode 6)

Balance-alb uses an adaptive load balancing policy. This mode provides fault tolerance, load balancing, and does not require any special switch support.

This mode Includes balance-transmit load balancing (balance-tlb) and receive-load balancing for IPv4 and IPv6 traffic. The bonding intercepts ARP replies sent by the local system and overwrites the source hardware address of one of the ports in the bond. ARP negotiation manages the receive-load balancing. Therefore, different ports use different hardware addresses for the server.

The primary option defines the preferred port of the bonding interface. With the bonding option tlb_dynamic_lb=0, this bonding mode uses the xmit_hash_policy bonding option to balance transmit. See description xmit_hash_policy bonding parameter.

Additional resources

/usr/share/doc/kernel-doc-< version
>/Documentation/networking/bonding.rst provided by the kernel-doc package
/usr/share/doc/kernel-doc-< version
>/Documentation/networking/bonding.txt provided by the kernel-doc package
Which bonding modes work when used with a bridge that virtual machine guests or containers connect to?
How are the values for different policies in “xmit_hash_policy” bonding parameter calculated?

9.13. The xmit_hash_policy bonding parameter

The xmit_hash_policy load balancing parameter selects the transmit hash policy for a node selection in the balance-xor, 802.3ad, balance-alb, and balance-tlb modes. It is only applicable to mode 5 and 6 if the tlb_dynamic_lb parameter is 0. The possible values of this parameter are layer2, layer2+3, layer3+4, encap2+3, encap3+4, and vlan+srcmac.

Refer the table for details:

Policy or Network layers

Layer2

Layer2+3

Layer3+4

encap2+3

encap3+4

VLAN+srcmac

Uses

XOR of source and destination MAC addresses and Ethernet protocol type

XOR of source and destination MAC addresses and IP addresses

XOR of source and destination ports and IP addresses

XOR of source and destination MAC addresses and IP addresses inside a supported tunnel, for example, Virtual Extensible LAN (VXLAN). This mode relies on skb_flow_dissect() function to obtain the header fields

XOR of source and destination ports and IP addresses inside a supported tunnel, for example, VXLAN. This mode relies on skb_flow_dissect() function to obtain the header fields

XOR of VLAN ID and source MAC vendor and source MAC device

Placement of traffic

All traffic to a particular network peer on the same underlying network interface

All traffic to a particular IP address on the same underlying network interface

All traffic to a particular IP address and port on the same underlying network interface

Primary choice

If network traffic is between this system and multiple other systems in the same broadcast doma0in

If network traffic between this system and multiple other systems goes through a default gateway

If network traffic between this system and another system uses the same IP addresses but goes through multiple ports

The encapsulated traffic is between the source system and multiple other systems using multiple IP addresses

The encapsulated traffic is between the source system and other systems using multiple port numbers

If the bond carries network traffic, from multiple containers or virtual machines (VM), that expose their MAC address directly to the external network such as the bridge network, and you can not configure a switch for Mode 2 or Mode 4

Secondary choice

If network traffic is mostly between this system and multiple other systems behind a default gateway

If network traffic is mostly between this system and another system

Compliant

802.3ad

Not 802.3ad

Default policy

This is the default policy if no configuration is provided

For non-IP traffic, the formula is the same as for the layer2 transmit policy

Chapter 10. Configuring a VPN connection

A virtual private network (VPN) is a way of connecting to a local network over the Internet. IPsec provided by Libreswan is the preferred method for creating a VPN. Libreswan is a user-space IPsec implementation for VPN. A VPN enables the communication between your LAN, and another, remote LAN by setting up a tunnel across an intermediate network such as the Internet. For security reasons, a VPN tunnel always uses authentication and encryption. For cryptographic operations, Libreswan uses the NSS library.

10.1. Configuring a VPN connection with control-center

If you use Red Hat Enterprise Linux with a graphical interface, you can configure a VPN connection in the GNOME control-center.

Prerequisites

The NetworkManager-libreswan-gnome package is installed.

Procedure

Press the

Super

key, type Settings, and press

Enter

to open the control-center application.
Select the Network entry on the left.
Click the

+

icon.
Select VPN.
Select the Identity menu entry to see the basic configuration options:

General

Gateway — The name or IP address of the remote VPN gateway.

Authentication

Type
- IKEv2 (Certificate)– client is authenticated by certificate. It is more secure (default).
- IKEv1 (XAUTH) – client is authenticated by user name and password, or a pre-shared key (PSK).
  
  The following configuration settings are available under the Advanced section:
  
  Figure 10.1. Advanced options of a VPN connection
  
  Warning
  
  When configuring an IPsec-based VPN connection using the gnome-control-center application, the Advanced dialog displays the configuration, but it does not allow any changes. As a consequence, users cannot change any advanced IPsec options. Use the nm-connection-editor or nmcli tools instead to perform configuration of the advanced properties.
  
  Identification
- Domain — If required, enter the Domain Name.
  
  Security
- Phase1 Algorithms — corresponds to the ike Libreswan parameter — enter the algorithms to be used to authenticate and set up an encrypted channel.
- Phase2 Algorithms — corresponds to the esp Libreswan parameter — enter the algorithms to be used for the IPsec negotiations.
  
  Check the Disable PFS field to turn off Perfect Forward Secrecy (PFS) to ensure compatibility with old servers that do not support PFS.
- Phase1 Lifetime — corresponds to the ikelifetime Libreswan parameter — how long the key used to encrypt the traffic will be valid.
- Phase2 Lifetime — corresponds to the salifetime Libreswan parameter — how long a particular instance of a connection should last before expiring.
  
  Note that the encryption key should be changed from time to time for security reasons.
- Remote network — corresponds to the rightsubnet Libreswan parameter — the destination private remote network that should be reached through the VPN.
  
  Check the narrowing field to enable narrowing. Note that it is only effective in IKEv2 negotiation.
- Enable fragmentation — corresponds to the fragmentation Libreswan parameter — whether or not to allow IKE fragmentation. Valid values are yes (default) or no.
- Enable Mobike — corresponds to the mobike Libreswan parameter — whether to allow Mobility and Multihoming Protocol (MOBIKE, RFC 4555) to enable a connection to migrate its endpoint without needing to restart the connection from scratch. This is used on mobile devices that switch between wired, wireless, or mobile data connections. The values are no (default) or yes.
Select the IPv4 menu entry:

IPv4 Method
- Automatic (DHCP) — Choose this option if the network you are connecting to uses a DHCP server to assign dynamic IP addresses.
- Link-Local Only — Choose this option if the network you are connecting to does not have a DHCP server and you do not want to assign IP addresses manually. Random addresses will be assigned as per RFC 3927169.254/16.
- Manual — Choose this option if you want to assign IP addresses manually.
- Disable — IPv4 is disabled for this connection.
  
  DNS
  
  In the DNS section, when Automatic is ON, switch it to OFF to enter the IP address of a DNS server you want to use separating the IPs by comma.
  
  Routes
  
  Note that in the Routes section, when Automatic is ON, routes from DHCP are used, but you can also add additional static routes. When OFF, only static routes are used.
- Address — Enter the IP address of a remote network or host.
- Netmask — The netmask or prefix length of the IP address entered above.
- Gateway — The IP address of the gateway leading to the remote network or host entered above.
- Metric — A network cost, a preference value to give to this route. Lower values will be preferred over higher values.
  
  Use this connection only for resources on its network
  
  Select this check box to prevent the connection from becoming the default route. Selecting this option means that only traffic specifically destined for routes learned automatically over the connection or entered here manually is routed over the connection.
To configure IPv6 settings in a VPN connection, select the IPv6 menu entry:

IPv6 Method
- Automatic — Choose this option to use IPv6 Stateless Address AutoConfiguration (SLAAC) to create an automatic, stateless configuration based on the hardware address and Router Advertisements (RA).
- Automatic, DHCP only — Choose this option to not use RA, but request information from DHCPv6 directly to create a stateful configuration.
- Link-Local Only — Choose this option if the network you are connecting to does not have a DHCP server and you do not want to assign IP addresses manually. Random addresses will be assigned as per RFC 4862FE80::0.
- Manual — Choose this option if you want to assign IP addresses manually.
- Disable — IPv6 is disabled for this connection.
  
  Note that DNS, Routes, Use this connection only for resources on its network are common to IPv4 settings.
Once you have finished editing the VPN connection, click the

Add

button to customize the configuration or the

Apply

button to save it for the existing one.
Switch the profile to ON to active the VPN connection.

Additional resources

nm-settings-libreswan(5)

10.2. Configuring a VPN connection using nm-connection-editor

If you use Red Hat Enterprise Linux with a graphical interface, you can configure a VPN connection in the nm-connection-editor application.

Prerequisites

The NetworkManager-libreswan-gnome package is installed.
If you configure an Internet Key Exchange version 2 (IKEv2) connection:
- The certificate is imported into the IPsec network security services (NSS) database.
- The nickname of the certificate in the NSS database is known.

Procedure

Open a terminal, and enter:
```
$ nm-connection-editor
```
Click the

+

button to add a new connection.
Select the IPsec based VPN connection type, and click

Create

.
On the VPN tab:
1. Enter the host name or IP address of the VPN gateway into the Gateway field, and select an authentication type. Based on the authentication type, you must enter different additional information:
  - IKEv2 (Certifiate) authenticates the client by using a certificate, which is more secure. This setting requires the nickname of the certificate in the IPsec NSS database
  - IKEv1 (XAUTH) authenticates the user by using a user name and password (pre-shared key). This setting requires that you enter the following values:
    - User name
    - Password
    - Group name
    - Secret
2. If the remote server specifies a local identifier for the IKE exchange, enter the exact string in the Remote ID field. In the remote server runs Libreswan, this value is set in the server’s leftid parameter.
3. Optionally, configure additional settings by clicking the Advanced button. You can configure the following settings:
  - Identification
    - Domain — If required, enter the domain name.
  - Security
    - Phase1 Algorithms corresponds to the ike Libreswan parameter. Enter the algorithms to be used to authenticate and set up an encrypted channel.
    - Phase2 Algorithms corresponds to the esp Libreswan parameter. Enter the algorithms to be used for the IPsec negotiations.
      
      Check the Disable PFS field to turn off Perfect Forward Secrecy (PFS) to ensure compatibility with old servers that do not support PFS.
    - Phase1 Lifetime corresponds to the ikelifetime Libreswan parameter. This parameter defines how long the key used to encrypt the traffic is valid.
    - Phase2 Lifetime corresponds to the salifetime Libreswan parameter. This parameter defines how long a security association is valid.
  - Connectivity
    - Remote network corresponds to the rightsubnet Libreswan parameter and defines the destination private remote network that should be reached through the VPN.
      
      Check the narrowing field to enable narrowing. Note that it is only effective in the IKEv2 negotiation.
    - Enable fragmentation corresponds to the fragmentation Libreswan parameter and defines whether or not to allow IKE fragmentation. Valid values are yes (default) or no.
    - Enable Mobike corresponds to the mobike Libreswan parameter. The parameter defines whether to allow Mobility and Multihoming Protocol (MOBIKE) (RFC 4555) to enable a connection to migrate its endpoint without needing to restart the connection from scratch. This is used on mobile devices that switch between wired, wireless or mobile data connections. The values are no (default) or yes.
On the IPv4 Settings tab, select the IP assignment method and, optionally, set additional static addresses, DNS servers, search domains, and routes.
Save the connection.
Close nm-connection-editor.

Note

When you add a new connection by clicking the + button, NetworkManager creates a new configuration file for that connection and then opens the same dialog that is used for editing an existing connection. The difference between these dialogs is that an existing connection profile has a Details menu entry.

Additional resources

nm-settings-libreswan(5) man page

10.3. Configuring automatic detection and usage of ESP hardware offload to accelerate an IPsec connection

Offloading Encapsulating Security Payload (ESP) to the hardware accelerates IPsec connections over Ethernet. By default, Libreswan detects if hardware supports this feature and, as a result, enables ESP hardware offload. In case that the feature was disabled or explicitly enabled, you can switch back to automatic detection.

Prerequisites

The network card supports ESP hardware offload.
The network driver supports ESP hardware offload.
The IPsec connection is configured and works.

Procedure

Edit the Libreswan configuration file in the /etc/ipsec.d/ directory of the connection that should use automatic detection of ESP hardware offload support.
Ensure the nic-offload parameter is not set in the connection’s settings.
If you removed nic-offload, restart the ipsec service:
```
# systemctl restart ipsec
```

Verification

If the network card supports ESP hardware offload support, following these steps to verify the result:

Display the tx_ipsec and rx_ipsec counters of the Ethernet device the IPsec connection uses:
```
# ethtool -S enp1s0
 | egrep "_ipsec"
     tx_ipsec: 10
     rx_ipsec: 10
```
Send traffic through the IPsec tunnel. For example, ping a remote IP address:
```
# ping -c 5 remote_ip_address
```
Display the tx_ipsec and rx_ipsec counters of the Ethernet device again:
```
# ethtool -S enp1s0
 | egrep "_ipsec"
     tx_ipsec: 15
     rx_ipsec: 15
```
If the counter values have increased, ESP hardware offload works.

Additional resources

Configuring a VPN with IPsec

10.4. Configuring ESP hardware offload on a bond to accelerate an IPsec connection

Offloading Encapsulating Security Payload (ESP) to the hardware accelerates IPsec connections. If you use a network bond for fail-over reasons, the requirements and the procedure to configure ESP hardware offload are different from those using a regular Ethernet device. For example, in this scenario, you enable the offload support on the bond, and the kernel applies the settings to the ports of the bond.

Prerequisites

All network cards in the bond support ESP hardware offload.
The network driver supports ESP hardware offload on a bond device. In RHEL, only the ixgbe driver supports this feature.
The bond is configured and works.
The bond uses the active-backup mode. The bonding driver does not support any other modes for this feature.
The IPsec connection is configured and works.

Procedure

Enable ESP hardware offload support on the network bond:
```
# nmcli connection modify 
bond0
 ethtool.feature-esp-hw-offload on
```
This command enables ESP hardware offload support on the bond0 connection.
Reactivate the bond0 connection:
```
# nmcli connection up 
bond0
```
Edit the Libreswan configuration file in the /etc/ipsec.d/ directory of the connection that should use ESP hardware offload, and append the nic-offload=yes statement to the connection entry:
```
conn example
    ...
    nic-offload=yes
```
Restart the ipsec service:
```
# systemctl restart ipsec
```

Verification

Display the active port of the bond:

grep "Currently Active Slave" /proc/net/bonding/

bond0

Currently Active Slave:

enp1s0

Display the tx_ipsec and rx_ipsec counters of the active port:

ethtool -S

enp1s0

| egrep "_ipsec"

tx_ipsec: 10 rx_ipsec: 10

Send traffic through the IPsec tunnel. For example, ping a remote IP address:
```
# ping -c 5 
remote_ip_address
```
Display the tx_ipsec and rx_ipsec counters of the active port again:
```
# ethtool -S enp1s0 | egrep "_ipsec"
     tx_ipsec: 15
     rx_ipsec: 15
```
If the counter values have increased, ESP hardware offload works.

Additional resources

Configuring network bonding
Configuring a VPN with IPsec section in the Securing networks document

Chapter 11. Configuring IP tunnels

Similar to a VPN, an IP tunnel directly connects two networks over a third network, such as the Internet. However, not all tunnel protocols support encryption.

The routers in both networks that establish the tunnel requires at least two interfaces:

One interface that is connected to the local network
One interface that is connected to the network through which the tunnel is established.

To establish the tunnel, you create a virtual interface on both routers with an IP address from the remote subnet.

NetworkManager supports the following IP tunnels:

Generic Routing Encapsulation (GRE)
Generic Routing Encapsulation over IPv6 (IP6GRE)
Generic Routing Encapsulation Terminal Access Point (GRETAP)
Generic Routing Encapsulation Terminal Access Point over IPv6 (IP6GRETAP)
IPv4 over IPv4 (IPIP)
IPv4 over IPv6 (IPIP6)
IPv6 over IPv6 (IP6IP6)
Simple Internet Transition (SIT)

Depending on the type, these tunnels act either on layer 2 or 3 of the Open Systems Interconnection (OSI) model.

11.1. Configuring an IPIP tunnel using nmcli to encapsulate IPv4 traffic in IPv4 packets

An IP over IP (IPIP) tunnel operates on OSI layer 3 and encapsulates IPv4 traffic in IPv4 packets as described in RFC 2003.

Important

Data sent through an IPIP tunnel is not encrypted. For security reasons, use the tunnel only for data that is already encrypted, for example, by other protocols, such as HTTPS.

Note that IPIP tunnels support only unicast packets. If you require an IPv4 tunnel that supports multicast, see Configuring a GRE tunnel using nmcli to encapsulate layer-3 traffic in IPv4 packets.

For example, you can create an IPIP tunnel between two RHEL routers to connect two internal subnets over the Internet as shown in the following diagram:

IPIP tunnel

Prerequisites

Each RHEL router has a network interface that is connected to its local subnet.
Each RHEL router has a network interface that is connected to the Internet.
The traffic you want to send through the tunnel is IPv4 unicast.

Procedure

On the RHEL router in network A:
1. Create an IPIP tunnel interface named tun0:
```
# nmcli connection add type ip-tunnel ip-tunnel.mode ipip con-name tun0 ifname tun0 remote 198.51.100.5 local 203.0.113.10
```
  The remote and local parameters set the public IP addresses of the remote and the local routers.
2. Set the IPv4 address to the tun0 device:
```
# nmcli connection modify tun0 ipv4.addresses '10.0.1.1/30'
```
  Note that a /30 subnet with two usable IP addresses is sufficient for the tunnel.
3. Configure the tun0 connection to use a manual IPv4 configuration:
```
# nmcli connection modify tun0 ipv4.method manual
```
4. Add a static route that routes traffic to the 172.16.0.0/24 network to the tunnel IP on router B:
```
# nmcli connection modify tun0 +ipv4.routes "172.16.0.0/24 10.0.1.2"
```
5. Enable the tun0 connection.
```
# nmcli connection up tun0
```
6. Enable packet forwarding:
```
# echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf
# sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf
```

On the RHEL router in network B:

Create an IPIP tunnel interface named tun0:
```
# nmcli connection add type ip-tunnel ip-tunnel.mode ipip con-name tun0 ifname tun0 remote 203.0.113.10 local 198.51.100.5
```
The remote and local parameters set the public IP addresses of the remote and local routers.

Set the IPv4 address to the tun0 device:

nmcli connection modify tun0 ipv4.addresses '10.0.1.2/30'

Configure the tun0 connection to use a manual IPv4 configuration:
```
# nmcli connection modify tun0 ipv4.method manual
```
Add a static route that routes traffic to the 192.0.2.0/24 network to the tunnel IP on router A:
```
# nmcli connection modify tun0 +ipv4.routes "192.0.2.0/24 10.0.1.1"
```
Enable the tun0 connection.
```
# nmcli connection up tun0
```

Enable packet forwarding:

echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf

sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf

Verification steps

From each RHEL router, ping the IP address of the internal interface of the other router:
1. On Router A, ping 172.16.0.1:
```
# ping 172.16.0.1
```
2. On Router B, ping 192.0.2.1:
```
# ping 192.0.2.1
```

Additional resources

nmcli(1) man page
nm-settings(5) man page

11.2. Configuring a GRE tunnel using nmcli to encapsulate layer-3 traffic in IPv4 packets

A Generic Routing Encapsulation (GRE) tunnel encapsulates layer-3 traffic in IPv4 packets as described in RFC 2784. A GRE tunnel can encapsulate any layer 3 protocol with a valid Ethernet type.

Important

Data sent through a GRE tunnel is not encrypted. For security reasons, use the tunnel only for data that is already encrypted, for example, by other protocols, such as HTTPS.

For example, you can create a GRE tunnel between two RHEL routers to connect two internal subnets over the Internet as shown in the following diagram:

GRE tunnel

Note

The gre0 device name is reserved. Use gre1 or a different name for the device.

Prerequisites

Each RHEL router has a network interface that is connected to its local subnet.
Each RHEL router has a network interface that is connected to the Internet.

Procedure

On the RHEL router in network A:
1. Create a GRE tunnel interface named gre1:
```
# nmcli connection add type ip-tunnel ip-tunnel.mode gre con-name gre1 ifname gre1 remote 198.51.100.5 local 203.0.113.10
```
  The remote and local parameters set the public IP addresses of the remote and the local routers.
2. Set the IPv4 address to the gre1 device:
```
# nmcli connection modify gre1 ipv4.addresses '10.0.1.1/30'
```
  Note that a /30 subnet with two usable IP addresses is sufficient for the tunnel.
3. Configure the gre1 connection to use a manual IPv4 configuration:
```
# nmcli connection modify gre1 ipv4.method manual
```
4. Add a static route that routes traffic to the 172.16.0.0/24 network to the tunnel IP on router B:
```
# nmcli connection modify gre1 +ipv4.routes "172.16.0.0/24 10.0.1.2"
```
5. Enable the gre1 connection.
```
# nmcli connection up gre1
```
6. Enable packet forwarding:
```
# echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf
# sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf
```

On the RHEL router in network B:

Create a GRE tunnel interface named gre1:
```
# nmcli connection add type ip-tunnel ip-tunnel.mode gre con-name gre1 ifname gre1 remote 203.0.113.10 local 198.51.100.5
```
The remote and local parameters set the public IP addresses of the remote and the local routers.

Set the IPv4 address to the gre1 device:

nmcli connection modify gre1 ipv4.addresses '10.0.1.2/30'

Configure the gre1 connection to use a manual IPv4 configuration:
```
# nmcli connection modify gre1 ipv4.method manual
```
Add a static route that routes traffic to the 192.0.2.0/24 network to the tunnel IP on router A:
```
# nmcli connection modify gre1 +ipv4.routes "192.0.2.0/24 10.0.1.1"
```
Enable the gre1 connection.
```
# nmcli connection up gre1
```

Enable packet forwarding:

echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf

sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf

Verification steps

From each RHEL router, ping the IP address of the internal interface of the other router:
1. On Router A, ping 172.16.0.1:
```
# ping 172.16.0.1
```
2. On Router B, ping 192.0.2.1:
```
# ping 192.0.2.1
```

Additional resources

nmcli(1) man page
nm-settings(5) man page

11.3. Configuring a GRETAP tunnel to transfer Ethernet frames over IPv4

A Generic Routing Encapsulation Terminal Access Point (GRETAP) tunnel operates on OSI level 2 and encapsulates Ethernet traffic in IPv4 packets as described in RFC 2784.

Important

Data sent through a GRETAP tunnel is not encrypted. For security reasons, establish the tunnel over a VPN or a different encrypted connection.

For example, you can create a GRETAP tunnel between two RHEL routers to connect two networks using a bridge as shown in the following diagram:

GRETAP tunnel

Note

The gretap0 device name is reserved. Use gretap1 or a different name for the device.

Prerequisites

Each RHEL router has a network interface that is connected to its local network, and the interface has no IP configuration assigned.
Each RHEL router has a network interface that is connected to the Internet.

Procedure

On the RHEL router in network A:
1. Create a bridge interface named bridge0:
```
# nmcli connection add type bridge con-name bridge0 ifname bridge0
```
2. Configure the IP settings of the bridge:
```
# nmcli connection modify bridge0 ipv4.addresses '192.0.2.1/24'
# nmcli connection modify bridge0 ipv4.method manual
```
3. Add a new connection profile for the interface that is connected to local network to the bridge:
```
# nmcli connection add type ethernet slave-type bridge con-name bridge0-port1 ifname enp1s0 master bridge0
```
4. Add a new connection profile for the GRETAP tunnel interface to the bridge:
```
# nmcli connection add type ip-tunnel ip-tunnel.mode gretap slave-type bridge con-name bridge0-port2 ifname gretap1 remote 198.51.100.5 local 203.0.113.10 master bridge0
```
  The remote and local parameters set the public IP addresses of the remote and the local routers.
5. Optional: Disable the Spanning Tree Protocol (STP) if you do not need it:
```
# nmcli connection modify bridge0 bridge.stp no
```
  By default, STP is enabled and causes a delay before you can use the connection.
6. Configure that activating the bridge0 connection automatically activates the ports of the bridge:
```
# nmcli connection modify bridge0 connection.autoconnect-slaves 1
```
7. Active the bridge0 connection:
```
# nmcli connection up bridge0
```

On the RHEL router in network B:

Create a bridge interface named bridge0:

nmcli connection add type bridge con-name bridge0 ifname bridge0

Configure the IP settings of the bridge:

nmcli connection modify bridge0 ipv4.addresses '192.0.2.2/24'

nmcli connection modify bridge0 ipv4.method manual

Add a new connection profile for the interface that is connected to local network to the bridge:

nmcli connection add type ethernet slave-type bridge con-name bridge0-port1 ifname enp1s0 master bridge0

Add a new connection profile for the GRETAP tunnel interface to the bridge:

nmcli connection add type ip-tunnel ip-tunnel.mode gretap slave-type bridge con-name bridge0-port2 ifname gretap1 remote 203.0.113.10 local 198.51.100.5 master bridge0

The remote and local parameters set the public IP addresses of the remote and the local routers.

Optional: Disable the Spanning Tree Protocol (STP) if you do not need it:
```
# nmcli connection modify bridge0 bridge.stp no
```
Configure that activating the bridge0 connection automatically activates the ports of the bridge:
```
# nmcli connection modify bridge0 connection.autoconnect-slaves 1
```
Active the bridge0 connection:
```
# nmcli connection up bridge0
```

Verification steps

On both routers, verify that the enp1s0 and gretap1 connections are connected and that the CONNECTION column displays the connection name of the port:

nmcli device

nmcli device DEVICE TYPE STATE CONNECTION ... bridge0 bridge connected bridge0 enp1s0 ethernet connected bridge0-port1 gretap1 iptunnel connected bridge0-port2

From each RHEL router, ping the IP address of the internal interface of the other router:
1. On Router A, ping 192.0.2.2:
```
# ping 192.0.2.2
```
2. On Router B, ping 192.0.2.1:
```
# ping 192.0.2.1
```

Additional resources

nmcli(1) man page
nm-settings(5) man page

11.4. Additional resources

ip-link(8) man page

Chapter 12. Changing a hostname

The hostname of a system is the name on the system itself. You can set the name when you install RHEL, and you can change it afterwards.

12.1. Changing a hostname using nmcli

You can use the nmcli utility to update the system hostname. Note that other utilities, might use a different term, such as static or persistent hostname.

Procedure

Optional: Display the current hostname setting:

nmcli general hostname

old-hostname.example.com

Set the new hostname:

nmcli general hostname

new-hostname.example.com

NetworkManager automatically restarts the systemd-hostnamed to activate the new name. However, the following manual actions can be required if you do not want to reboot the host:
1. Restart all services that only read the hostname when the service starts:
```
# systemctl restart 
service_name
```
2. Active shell users must re-login for the changes to take effect.

Verification

Display the hostname:

nmcli general hostname

new-hostname.example.com

12.2. Changing a hostname using hostnamectl

You can use the hostnamectl utility to update the hostname. By default, this utility sets the following hostname types:

Static hostname: Stored in the /etc/hostname file. Typically, services use this name as the hostname.
Pretty hostname: A descriptive name, such as Proxy server in data center A.
Transient hostname: A fall-back value that is typically received from the network configuration.

Procedure

Optional: Display the current hostname setting:

hostnamectl status --static

old-hostname.example.com

Set the new hostname:
```
# hostnamectl set-hostname 
new-hostname.example.com
```
This command sets the static, pretty, and transient hostname to the new value. To set only a specific type, pass the --static, --pretty, or --transient option to the command.
The hostnamectl utility automatically restarts the systemd-hostnamed to activate the new name. However, the following manual actions can be required if you do not want to reboot the host:
1. Restart all services that only read the hostname when the service starts:
```
# systemctl restart 
service_name
```
2. Active shell users must re-login for the changes to take effect.

Verification

Display the hostname:

hostnamectl status --static

new-hostname.example.com

Additional resources

hostnamectl(1)
systemd-hostnamed.service(8)

Chapter 13. Legacy network scripts support in RHEL

By default, RHEL uses NetworkManager to configure and manage network connections, and the /usr/sbin/ifup and /usr/sbin/ifdown scripts use NetworkManager to process ifcfg files in the /etc/sysconfig/network-scripts/ directory.

Important

The legacy scripts are deprecated in RHEL 8 and will be removed in a future major version of RHEL. If you still use the legacy network scripts, for example, because you upgraded from an earlier version to RHEL 8, Red Hat recommends that you migrate your configuration to NetworkManager.

13.1. Installing the legacy network scripts

If you require the deprecated network scripts that processes the network configuration without using NetworkManager, you can install them. In this case, the /usr/sbin/ifup and /usr/sbin/ifdown scripts link to the deprecated shell scripts that manage the network configuration.

Procedure

Install the network-scripts package:
```
# yum install network-scripts
```

Chapter 14. Port mirroring

Network administrators can use port mirroring to replicate inbound and outbound network traffic being communicated from one network device to another. Administrators use port mirroring to monitor network traffic and collect network data to:

Debug networking issues and tune the network flow
Inspect and analyze the network traffic to troubleshoot networking problems
Detect an intrusion

14.1. Mirroring a network interface using nmcli

You can configure port mirroring using NetworkManager. The following procedure mirrors the network traffic from enp1s0 to enp7s0 by adding Traffic Control (tc) rules and filters to the enp1s0 network interface.

Prerequisites

A network interface to mirror the network traffic to.

Procedure

Add a network connection profile that you want to mirror the network traffic from:

nmcli connection add type ethernet ifname

enp1s0

con-name
enp1s0
autoconnect
no

Attach a prio qdisc to enp1s0 for the egress (outgoing) traffic with the 10: handle:
```
# nmcli connection modify 
enp1s0
 +tc.qdisc "root prio handle 10:"
```
The prio qdisc attached without children allows attaching filters.

Add a qdisc for the ingress traffic, with the ffff: handle:

nmcli connection modify

enp1s0

+tc.qdisc "ingress handle ffff:"

Add the following filters to match packets on the ingress and egress qdiscs, and to mirror them to enp7s0:

nmcli connection modify

enp1s0

+tc.tfilter "parent ffff: matchall action mirred egress mirror dev
enp7s0
"

nmcli connection modify

enp1s0

+tc.tfilter "parent 10: matchall action mirred egress mirror dev
enp7s0
"

The matchall filter matches all packets, and the mirred action redirects packets to destination.

Activate the connection:
```
# nmcli connection up 
enp1s0
```

Verification steps

Install the tcpdump utility:
```
# yum install tcpdump
```
Display the traffic mirrored on the target device (enp7s0):
```
# tcpdump -i 
enp7s0
```

Additional resources

How to capture network packets using tcpdump

Chapter 15. Configuring NetworkManager to ignore certain devices

By default, NetworkManager manages all devices except the lo (loopback) device. However, you can set certain devices as unmanaged to configure that NetworkManager ignores these devices. With this setting, you can manually manage these devices, for example, using a script.

15.1. Permanently configuring a device as unmanaged in NetworkManager

You can permanently configure devices as unmanaged based on several criteria, such as the interface name, MAC address, or device type.

To temporarily configure network devices as unmanaged, see Temporarily configuring a device as unmanaged in NetworkManager.

Procedure

Optional: Display the list of devices to identify the device or MAC address you want to set as unmanaged:

ip link show

... 2:

enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000

link/ether 52:54:00:74:79:56 brd ff:ff:ff:ff:ff:ff

...

Create the /etc/NetworkManager/conf.d/99-unmanaged-devices.conf file with the following content:
- To configure a specific interface as unmanaged, add:
```
[keyfile]
unmanaged-devices=interface-name:
enp1s0
```
- To configure a device with a specific MAC address as unmanaged, add:
```
[keyfile]
unmanaged-devices=mac:
52:54:00:74:79:56
```
- To configure all devices of a specific type as unmanaged, add:
```
[keyfile]
unmanaged-devices=type:ethernet
```
To set multiple devices as unmanaged, separate the entries in the unmanaged-devices parameter with semicolon:
Reload the NetworkManager service:
```
# systemctl reload NetworkManager
```

Verification steps

Display the list of devices:
```
# nmcli device status
DEVICE  TYPE      STATE      CONNECTION
enp1s0
  ethernet  unmanaged  --
...
```
The unmanaged state next to the enp1s0 device indicates that NetworkManager does not manage this device.

Additional resources

NetworkManager.conf(5) man page

15.2. Temporarily configuring a device as unmanaged in NetworkManager

You can temporarily configure devices as unmanaged.

Use this method, for example, for testing purposes. To permanently configure network devices as unmanaged, see Permanently configuring a device as unmanaged in NetworkManager.

Procedure

Optional: Display the list of devices to identify the device you want to set as unmanaged:

nmcli device status

DEVICE TYPE STATE CONNECTION

enp1s0

ethernet disconnected -- ...

Set the enp1s0 device to the unmanaged state:
```
# nmcli device set 
enp1s0
 managed no
```

Verification steps

Display the list of devices:
```
# nmcli device status
DEVICE  TYPE      STATE      CONNECTION
enp1s0
  ethernet  unmanaged  --
...
```
The unmanaged state next to the enp1s0 device indicates that NetworkManager does not manage this device.

Additional resources

NetworkManager.conf(5) man page

Chapter 16. Configuring network devices to accept traffic from all MAC addresses

Network devices usually intercept and read packets that their controller is programmed to receive. You can configure the network devices to accept traffic from all MAC addresses in a virtual switch or at the port group level.

You can use this network mode to:

Diagnose network connectivity issues
Monitor network activity for security reasons
Intercept private data-in-transit or intrusion in the network

You can enable this mode for any kind of network device, except InfiniBand.

16.1. Temporarily configuring a device to accept all traffic

You can use the ip utility to temporary configure a network device to accept all traffic regardless of the MAC addresses.

Procedure

Optional: Display the network interfaces to identify the one for which you want to receive all traffic:

ip address show

1: enp1s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000 link/ether 98:fa:9b:a4:34:09 brd ff:ff:ff:ff:ff:ff ...

Modify the device to enable or disable this property:
- To enable the accept-all-mac-addresses mode for enp1s0:
```
# ip link set 
enp1s0
 promisc on
```
- To disable the accept-all-mac-addresses mode for enp1s0:
```
# ip link set 
enp1s0
 promisc off
```

Verification steps

Verify that the accept-all-mac-addresses mode is enabled:

ip link show

enp1s0

1: enp1s0: <NO-CARRIER,BROADCAST,MULTICAST,

PROMISC

,UP> mtu 1500 qdisc fq_codel state DOWN mode DEFAULT group default qlen 1000 link/ether 98:fa:9b:a4:34:09 brd ff:ff:ff:ff:ff:ff

The PROMISC flag in the device description indicates that the mode is enabled.

16.2. Permanently configuring a network device to accept all traffic using nmcli

You can use the nmcli utility to permanently configure a network device to accept all traffic regardless of the MAC addresses.

Procedure

Optional: Display the network interfaces to identify the one for which you want to receive all traffic:

ip address show

1: enp1s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000 link/ether 98:fa:9b:a4:34:09 brd ff:ff:ff:ff:ff:ff ...

You can create a new connection, if you do not have any.

Modify the network device to enable or disable this property.
- To enable the ethernet.accept-all-mac-addresses mode for enp1s0:
```
# nmcli connection modify 
enp1s0
 ethernet.accept-all-mac-addresses yes
```
- To disable the accept-all-mac-addresses mode for enp1s0:
```
# nmcli connection modify 
enp1s0
 ethernet.accept-all-mac-addresses no
```
Apply the changes, reactivate the connection:
```
# nmcli connection up 
enp1s0
```

Verification steps

Verify that the ethernet.accept-all-mac-addresses mode is enabled:
```
# nmcli connection show 
enp1s0

...
802-3-ethernet.accept-all-mac-addresses:1     (true)
```
The 802-3-ethernet.accept-all-mac-addresses: true indicates that the mode is enabled.

16.3. Permanently configuring a network device to accept all traffic using nmstatectl

You can use the nmstatectl utility to permanently configure a network device to accept all traffic regardless of the MAC addresses.

Prerequisites

The nmstate package is installed.
The enp1s0.yml file that you used to configure the device is available.

Procedure

Edit the existing enp1s0.yml file for the enp1s0 connection and add the following content to it:

---

interfaces:

- name:

enp1s0

type: ethernet

state: up

accept -all-mac-address:

true

Apply the network settings:
```
# nmstatectl apply ~/enp1s0.yml
```

Verification steps

Verify that the 802-3-ethernet.accept-all-mac-addresses mode is enabled:
```
# nmstatectl show 
enp1s0

interfaces:
  - name: enp1s0
    type: ethernet
    state: up
    accept-all-mac-addresses:     true
...
```
The 802-3-ethernet.accept-all-mac-addresses: true indicates that the mode is enabled.

Additional resources

nmstatectl(8) man page
/usr/share/doc/nmstate/examples/ directory

Chapter 17. Setting up an 802.1x network authentication service for LAN clients using hostapd with FreeRADIUS backend

The IEEE 802.1X standard defines secure authentication and authorization methods to protect networks from unauthorized clients. Using the hostapd service and FreeRADIUS, you can provide network access control (NAC) in your network.

In this documentation, the RHEL host acts as a bridge to connect different clients with an existing network. However, the RHEL host grants only authenticated clients access to the network.

rhel authenticator 802 1x

17.1. Prerequisites

A clean installation of FreeRADIUS.

If the freeradius package is already installed, remove the /etc/raddb/ directory, uninstall and then install the package again. Do not reinstall the package using the yum reinstall command, because the permissions and symbolic links in the /etc/raddb/ directory are then different.

17.2. Setting up the bridge on the authenticator

A network bridge is a link-layer device which forwards traffic between hosts and networks based on a table of MAC addresses. If you set up RHEL as an 802.1X authenticator, add both the interfaces on which to perform authentication and the LAN interface to the bridge.

Prerequisites

The server has multiple Ethernet interfaces.

Procedure

Create the bridge interface:

nmcli connection add type bridge con-name br0 ifname br0

Assign the Ethernet interfaces to the bridge:

nmcli connection add type ethernet slave-type bridge con-name br0-port1 ifname enp1s0 master br0

nmcli connection add type ethernet slave-type bridge con-name br0-port2 ifname enp7s0 master br0

nmcli connection add type ethernet slave-type bridge con-name br0-port3 ifname enp8s0 master br0

nmcli connection add type ethernet slave-type bridge con-name br0-port4 ifname enp9s0 master br0

Enable the bridge to forward extensible authentication protocol over LAN (EAPOL) packets:
```
# nmcli connection modify br0 group-forward-mask 8
```

Configure the connection to automatically activate the ports:

nmcli connection modify br0 connection.autoconnect-slaves 1

Activate the connection:
```
# nmcli connection up br0
```

Verification

Display the link status of Ethernet devices that are ports of a specific bridge:

ip link show master br0

3: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master br0 state UP mode DEFAULT group default qlen 1000 link/ether 52:54:00:62:61:0e brd ff:ff:ff:ff:ff:ff ...

Verify if forwarding of EAPOL packets is enabled on the br0 device:
```
# cat /sys/class/net/br0/bridge/group_fwd_mask
0x8
```
If the command returns 0x8, forwarding is enabled.

Additional resources

nm-settings(5) man page

17.3. Certificate requirements by FreeRADIUS

For a secure FreeRADIUS service, you require TLS certificates for different purposes:

A TLS server certificate for encrypted connections to the server. Use a trusted certificate authority (CA) to issue the certificate.

The server certificate requires the extended key usage (EKU) field set to TLS Web Server Authentication.
Client certificates issued by the same CA for extended authentication protocol transport layer security (EAP-TLS). EAP-TLS provides certificate-based authentication and is enabled by default.

The client certificates require their EKU field set to TLS Web Client Authentication.

Warning

To secure connection, use your company’s CA or create your own CA to issue certificates for FreeRADIUS. If you use a public CA, you allow it to authenticate users and issue client certificates for EAP-TLS.

17.4. Creating a set of certificates on a FreeRADIUS server for testing purposes

For testing purposes, the freeradius package installs scripts and configuration files in the /etc/raddb/certs/ directory to create your own certificate authority (CA) and issue certificates.

Important

If you use the default configuration, certificates generated by these scripts expire after 60 days and keys use an insecure password (“whatever”). However, you can customize the CA, server, and client configuration.

After you perform the procedure, the following files, which you require later in this documentation, are created:

/etc/raddb/certs/ca.pem: CA certificate
/etc/raddb/certs/server.key: Private key of the server certificate
/etc/raddb/certs/server.pem: Server certificate
/etc/raddb/certs/client.key: Private key of the client certificate
/etc/raddb/certs/client.pem: Client certificate

Prerequisites

You installed the freeradius package.

Procedure

Change into the /etc/raddb/certs/ directory:
```
# cd /etc/raddb/certs/
```

Optional: Customize the CA configuration:

...
[ req ]
default_bits            = 2048
input_password          = ca_password
output_password         = ca_password
...
[certificate_authority]
countryName             = US
stateOrProvinceName     = North Carolina
localityName            = Raleigh
organizationName        = Example Inc.
emailAddress            = [email protected]
commonName              = "Example Certificate Authority"
...

Optional: Customize the server configuration:

...
[ CA_default ]
default_days            = 730
...
[ req ]
distinguished_name      = server
default_bits            = 2048
input_password          = key_password
output_password         = key_password
...
[server]
countryName             = US
stateOrProvinceName     = North Carolina
localityName            = Raleigh
organizationName        = Example Inc.
emailAddress            = [email protected]
commonName              = "Example Server Certificate"
...

Optional: Customize the client configuration:

...
[ CA_default ]
default_days            = 365
...
[ req ]
distinguished_name      = client
default_bits            = 2048
input_password          = password_on_private_key
output_password         = password_on_private_key
...
[client]
countryName             = US
stateOrProvinceName     = North Carolina
localityName            = Raleigh
organizationName        = Example Inc.
emailAddress            = [email protected]
commonName              = [email protected]
...

Create the certificates:
```
# make all
```
Change the group on the /etc/raddb/certs/server.pem file to radiusd:
```
# chgrp radiusd /etc/raddb/certs/server.pem
*
```

Additional resources

/etc/raddb/certs/README.md

17.5. Configuring FreeRADIUS to authenticate network clients securely using EAP

FreeRADIUS supports different methods of the Extensible authentication protocol (EAP). However, for a secure network, configure FreeRADIUS to support only the following secure EAP authentication methods:

EAP-TLS (transport layer security) uses a secure TLS connection to authenticate clients using certificates. To use EAP-TLS, you need TLS client certificates for each network client and a server certificate for the server. Note that the same certificate authority (CA) must have issued the certificates. Always use your own CA to create certificates, because all client certificates issued by the CA you use can authenticate to your FreeRADIUS server.
EAP-TTLS (tunneled transport layer security) uses a secure TLS connection and authenticates clients using mechanisms, such as password authentication protocol (PAP) or challenge handshake authentication protocol (CHAP). To use EAP-TTLS, you need a TLS server certificate.
EAP-PEAP (protected extensible authentication protocol) uses a secure TLS connection as the outer authentication protocol to set up the tunnel. The authenticator authenticates the certificate of the RADIUS server. Afterwards, the supplicant authenticates through the encrypted tunnel using Microsoft challenge handshake authentication protocol version 2 (MS-CHAPv2) or other methods.

Note

The default FreeRADIUS configuration files serve as documentation and describe all parameters and directives. If you want to disable certain features, comment them out instead of removing the corresponding parts in the configuration files. This enables you to preserve the structure of the configuration files and the included documentation.

Prerequisites

You installed the freeradius package.
The configuration files in the /etc/raddb/ directory are unchanged and as provided by the freeradius package.
The following files exist on the server:
- TLS private key of the FreeRADIUS host: /etc/raddb/certs/server.key
- TLS server certificate of the FreeRADIUS host: /etc/raddb/certs/server.pem
- TLS CA certificate: /etc/raddb/certs/ca.pem
If you store the files in a different location or if they have different names, set the private_key_file, certificate_file, and ca_file parameters in the /etc/raddb/mods-available/eap file accordingly.

Procedure

If the /etc/raddb/certs/dh with Diffie-Hellman (DH) parameters does not exist, create one. For example, to create a DH file with a 2048 bits prime, enter:
```
# openssl dhparam -out /etc/raddb/certs/dh 2048
```
For security reasons, do not use a DH file with less than a 2048 bits prime. Depending on the number of bits, the creation of the file can take several minutes.

Set secure permissions on the TLS private key, server certificate, CA certificate, and the file with DH parameters:

chmod 640 /etc/raddb/certs/server.key /etc/raddb/certs/server.pem /etc/raddb/certs/ca.pem /etc/raddb/certs/dh

chown root:radiusd /etc/raddb/certs/server.key /etc/raddb/certs/server.pem /etc/raddb/certs/ca.pem /etc/raddb/certs/dh

Edit the /etc/raddb/mods-available/eap file:
1. Set the password of the private key in the private_key_password parameter:
```
eap {
    ...
    tls-config tls-common {
        ...
        private_key_password = key_password
        ...
    }
}
```
2. Depending on your environment, set the default_eap_type parameter in the eap directive to your primary EAP type you use:
```
eap {
    ...
    default_eap_type = ttls
    ...
}
```
  For a secure environment, use only ttls, tls, or peap.
3. Comment out the md5 directives to disable the insecure EAP-MD5 authentication method:
```
eap {
    ...
    # md5 {
    # }
    ...
}
```
  Note that, in the default configuration file, other insecure EAP authentication methods are commented out by default.

Edit the /etc/raddb/sites-available/default file, and comment out all authentication methods other than eap:

authenticate {
    ...
    # Auth-Type PAP {
    #     pap
    # }

    # Auth-Type CHAP {
    #     chap
    # }

    # Auth-Type MS-CHAP {
    #     mschap
    # }

    # mschap

    # digest
    ...
}

This leaves only EAP enabled and disables plain-text authentication methods.

Edit the /etc/raddb/clients.conf file:
1. Set a secure password in the localhost and localhost_ipv6 client directives:
```
client localhost {
    ipaddr = 127.0.0.1
    ...
    secret = client_password
    ...
}

client localhost_ipv6 {
    ipv6addr = ::1
    secret = client_password
}
```
2. If RADIUS clients, such as network authenticators, on remote hosts should be able to access the FreeRADIUS service, add corresponding client directives for them:
```
client hostapd.example.org {
    ipaddr = 192.0.2.2/32
    secret = client_password
}
```
  The ipaddr parameter accepts IPv4 and IPv6 addresses, and you can use the optional classless inter-domain routing (CIDR) notation to specify ranges. However, you can set only one value in this parameter. For example, to grant access to an IPv4 and IPv6 address, add two client directives.
  
  Use a descriptive name for the client directive, such as a hostname or a word that describes where the IP range is used.
If you want to use EAP-TTLS or EAP-PEAP, add the users to the /etc/raddb/users file:
```
example_user
        Cleartext-Password := "user_password
"
```
For users who should use certificate-based authentication (EAP-TLS), do not add any entry.

Verify the configuration files:

radiusd -XC

... Configuration appears to be OK

Enable and start the radiusd service:
```
# systemctl enable --now radiusd
```

Verification

Testing EAP-TTLS authentication against a FreeRADIUS server or authenticator
Testing EAP-TLS authentication against a FreeRADIUS server or authenticator

Troubleshooting

Stop the radiusd service:
```
# systemctl stop radiusd
```

Start the service in debug mode:

radiusd -X

... Ready to process requests

Perform authentication tests on the FreeRADIUS host, as referenced in the Verification section.

Next steps

Disable unrequired authentication methods and other features you do not use.

17.6. Configuring hostapd as an authenticator in a wired network

The host access point daemon (hostapd) service can act as an authenticator in a wired network to provide 802.1X authentication. For this, the hostapd service requires a RADIUS server that authenticates the clients.

The hostapd service provides an integrated RADIUS server. However, use the integrated RADIUS server only for testing purposes. For production environments, use FreeRADIUS server, which supports additional features, such as different authentication methods and access control.

Important

The hostapd service does not interact with the traffic plane. The service acts only as an authenticator. For example, use a script or service that uses the hostapd control interface to allow or deny traffic based on the result of authentication events.

Prerequisites

You installed the hostapd package.
The FreeRADIUS server has been configured, and it is ready to authenticate clients.

Procedure

Create the /etc/hostapd/hostapd.conf file with the following content:

# General settings of hostapd
# ===========================

# Control interface settings
ctrl_interface=/var/run/hostapd
ctrl_interface_group=wheel

# Enable logging for all modules
logger_syslog=-1
logger_stdout=-1

# Log level
logger_syslog_level=2
logger_stdout_level=2


# Wired 802.1X authentication
# ===========================

# Driver interface type
driver=wired

# Enable IEEE 802.1X authorization
ieee8021x=1

# Use port access entry (PAE) group address
# (01:80:c2:00:00:03) when sending EAPOL frames
use_pae_group_addr=1


# Network interface for authentication requests
interface=br0


# RADIUS client configuration
# ===========================

# Local IP address used as NAS-IP-Address
own_ip_addr=192.0.2.2

# Unique NAS-Identifier within scope of RADIUS server
nas_identifier=hostapd.example.org

# RADIUS authentication server
auth_server_addr=192.0.2.1
auth_server_port=1812
auth_server_shared_secret=client_password

# RADIUS accounting server
acct_server_addr=192.0.2.1
acct_server_port=1813
acct_server_shared_secret=client_password

For further details about the parameters used in this configuration, see their descriptions in the /usr/share/doc/hostapd/hostapd.conf example configuration file.

Enable and start the hostapd service:
```
# systemctl enable --now hostapd
```

Verification

See:
- Testing EAP-TTLS authentication against a FreeRADIUS server or authenticator
- Testing EAP-TLS authentication against a FreeRADIUS server or authenticator

Troubleshooting

Stop the hostapd service:
```
# systemctl stop hostapd
```
Start the service in debug mode:
```
# hostapd -d /etc/hostapd/hostapd.conf
```
Perform authentication tests on the FreeRADIUS host, as referenced in the Verification section.

Additional resources

hostapd.conf(5) man page
/usr/share/doc/hostapd/hostapd.conf file

17.7. Testing EAP-TTLS authentication against a FreeRADIUS server or authenticator

To test if authentication using extensible authentication protocol (EAP) over tunneled transport layer security (EAP-TTLS) works as expected, run this procedure:

After you set up the FreeRADIUS server
After you set up the hostapd service as an authenticator for 802.1X network authentication.

The output of the test utilities used in this procedure provide additional information about the EAP communication and help you to debug problems.

Prerequisites

When you want to authenticate to:
- A FreeRADIUS server:
  - The eapol_test utility, provided by the hostapd package, is installed.
  - The client, on which you run this procedure, has been authorized in the FreeRADIUS server’s client databases.
- An authenticator, the wpa_supplicant utility, provided by the same-named package, is installed.
You stored the certificate authority (CA) certificate in the /etc/pki/tls/certs/ca.pem file.

Procedure

Create the /etc/wpa_supplicant/wpa_supplicant-TTLS.conf file with the following content:

ap_scan=0

network={
    eap=TTLS
    eapol_flags=0
    key_mgmt=IEEE8021X

    # Anonymous identity (sent in unencrypted phase 1)
    # Can be any string
    anonymous_identity="anonymous"

    # Inner authentication (sent in TLS-encrypted phase 2)
    phase2="auth=PAP"
    identity="example_user"
    password="user_password"

    # CA certificate to validate the RADIUS server's identity
    ca_cert="/etc/pki/tls/certs/ca.pem"
}

To authenticate to:
- A FreeRADIUS server, enter:
```
# eapol_test -c 
/etc/wpa_supplicant/wpa_supplicant-TTLS.conf
 -a 192.0.2.1
 -s client_password
...
EAP: Status notification: remote certificate verification (param=success)
...
CTRL-EVENT-EAP-SUCCESS EAP authentication completed successfully
...
SUCCESS
```
  The -a option defines the IP address of the FreeRADIUS server, and the -s option specifies the password for the host on which you run the command in the FreeRADIUS server’s client configuration.
- An authenticator, enter:
```
# wpa_supplicant -c 
/etc/wpa_supplicant/wpa_supplicant-TTLS.conf
 -D wired -i enp0s31f6
...
enp0s31f6: CTRL-EVENT-EAP-SUCCESS EAP authentication completed successfully
...
```
  The -i option specifies the network interface name on which wpa_supplicant sends out extended authentication protocol over LAN (EAPOL) packets.
  
  For more debugging information, pass the -d option to the command.

Additional resources

/usr/share/doc/wpa_supplicant/wpa_supplicant.conf file

17.8. Testing EAP-TLS authentication against a FreeRADIUS server or authenticator

To test if authentication using extensible authentication protocol (EAP) transport layer security (EAP-TLS) works as expected, run this procedure:

After you set up the FreeRADIUS server
After you set up the hostapd service as an authenticator for 802.1X network authentication.

The output of the test utilities used in this procedure provide additional information about the EAP communication and help you to debug problems.

Prerequisites

When you want to authenticate to:
- A FreeRADIUS server:
  - The eapol_test utility, provided by the hostapd package, is installed.
  - The client, on which you run this procedure, has been authorized in the FreeRADIUS server’s client databases.
- An authenticator, the wpa_supplicant utility, provided by the same-named package, is installed.
You stored the certificate authority (CA) certificate in the /etc/pki/tls/certs/ca.pem file.
The CA that issued the client certificate is the same that issued the server certificate of the FreeRADIUS server.
You stored the client certificate in the /etc/pki/tls/certs/client.pem file.
You stored the private key of the client in the /etc/pki/tls/private/client.key

Procedure

Create the /etc/wpa_supplicant/wpa_supplicant-TLS.conf file with the following content:

ap_scan=0

network={
    eap=TLS
    eapol_flags=0
    key_mgmt=IEEE8021X

    identity="[email protected]"
    client_cert="/etc/pki/tls/certs/client.pem"
    private_key="/etc/pki/tls/private/client.key"
    private_key_passwd="password_on_private_key"

    # CA certificate to validate the RADIUS server's identity
    ca_cert="/etc/pki/tls/certs/ca.pem"
}

To authenticate to:
- A FreeRADIUS server, enter:
```
# eapol_test -c 
/etc/wpa_supplicant/wpa_supplicant-TLS.conf
 -a 192.0.2.1
 -s client_password
...
EAP: Status notification: remote certificate verification (param=success)
...
CTRL-EVENT-EAP-SUCCESS EAP authentication completed successfully
...
SUCCESS
```
  The -a option defines the IP address of the FreeRADIUS server, and the -s option specifies the password for the host on which you run the command in the FreeRADIUS server’s client configuration.
- An authenticator, enter:
```
# wpa_supplicant -c 
/etc/wpa_supplicant/wpa_supplicant-TLS.conf
 -D wired -i enp0s31f6
...
enp0s31f6: CTRL-EVENT-EAP-SUCCESS EAP authentication completed successfully
...
```
  The -i option specifies the network interface name on which wpa_supplicant sends out extended authentication protocol over LAN (EAPOL) packets.
  
  For more debugging information, pass the -d option to the command.

Additional resources

/usr/share/doc/wpa_supplicant/wpa_supplicant.conf file

17.9. Blocking and allowing traffic based on hostapd authentication events

The hostapd service does not interact with the traffic plane. The service acts only as an authenticator. However, you can write a script to allow and deny traffic based on the result of authentication events.

Important

This procedure is not supported and is no enterprise-ready solution. It only demonstrates how to block or allow traffic by evaluating events retrieved by hostapd_cli.

When the 802-1x-tr-mgmt systemd service starts, RHEL blocks all traffic on the listen port of hostapd except extensible authentication protocol over LAN (EAPOL) packets and uses the hostapd_cli utility to connect to the hostapd control interface. The /usr/local/bin/802-1x-tr-mgmt script then evaluates events. Depending on the different events received by hostapd_cli, the script allows or blocks traffic for MAC addresses. Note that, when the 802-1x-tr-mgmt service stops, all traffic is automatically allowed again.

Perform this procedure on the hostapd server.

Prerequisites

The hostapd service has been configured, and the service is ready to authenticate clients.

Procedure

Create the /usr/local/bin/802-1x-tr-mgmt file with the following content:

#!/bin/sh

if [ "x$1" == "xblock_all" ]
then

    nft delete table bridge tr-mgmt-br0 2>/dev/null || true
    nft -f - << EOF
table bridge tr-mgmt-br0 {
        set allowed_macs {
                type ether_addr
        }

        chain accesscontrol {
                ether saddr @allowed_macs accept
                ether daddr @allowed_macs accept
                drop
        }

        chain forward {
                type filter hook forward priority 0; policy accept;
                meta ibrname "br0" jump accesscontrol
        }
}
EOF
    echo "802-1x-tr-mgmt Blocking all traffic through br0. Traffic for given host will be allowed after 802.1x authentication"

elif [ "x$1" == "xallow_all" ]
then

    nft delete table bridge tr-mgmt-br0
    echo "802-1x-tr-mgmt Allowed all forwarding again"

fi

case ${2:-NOTANEVENT} in

    AP-STA-CONNECTED | CTRL-EVENT-EAP-SUCCESS | CTRL-EVENT-EAP-SUCCESS2)
        nft add element bridge tr-mgmt-br0 allowed_macs { $3 }
        echo "$1: Allowed traffic from $3"
        ;;

    AP-STA-DISCONNECTED | CTRL-EVENT-EAP-FAILURE)
        nft delete element bridge tr-mgmt-br0 allowed_macs { $3 }
        echo "802-1x-tr-mgmt $1: Denied traffic from $3"
        ;;

esac

Create the /etc/systemd/system/[email protected] systemd service file with the following content:

[Unit]
Description=Example 802.1x traffic management for hostapd
After=hostapd.service
After=sys-devices-virtual-net-%i.device

[Service]
Type=simple
ExecStartPre=-/bin/sh -c '/usr/sbin/tc qdisc del dev %i ingress > /dev/null 2>&1'
ExecStartPre=-/bin/sh -c '/usr/sbin/tc qdisc del dev %i clsact > /dev/null 2>&1'
ExecStartPre=/usr/sbin/tc qdisc add dev %i clsact
ExecStartPre=/usr/sbin/tc filter add dev %i ingress pref 10000 protocol 0x888e matchall action ok index 100
ExecStartPre=/usr/sbin/tc filter add dev %i ingress pref 10001 protocol all matchall action drop index 101
ExecStart=/usr/sbin/hostapd_cli -i %i -a /usr/local/bin/802-1x-tr-mgmt
ExecStopPost=-/usr/sbin/tc qdisc del dev %i clsact

[Install]
WantedBy=multi-user.target

Reload systemd:
```
# systemctl daemon-reload
```
Enable and start the 802-1x-tr-mgmt service with the interface name hostapd is listening on:
```
# systemctl enable --now [email protected]
```

Verification

Authenticate with a client to the network. See:
- Testing EAP-TTLS authentication against a FreeRADIUS server or authenticator
- Testing EAP-TLS authentication against a FreeRADIUS server or authenticator

Additional resources

systemd.service(5) man page

Chapter 18. Authenticating a RHEL client to the network using the 802.1X standard with a certificate stored on the file system

Administrators frequently use port-based Network Access Control (NAC) based on the IEEE 802.1X standard to protect a network from unauthorized LAN and Wi-Fi clients.

18.1. Configuring 802.1X network authentication on an existing Ethernet connection using nmcli

Using the nmcli utility, you can configure the client to authenticate itself to the network. For example, configure TLS authentication in an existing NetworkManager Ethernet connection profile named enp1s0 to authenticate to the network.

Prerequisites

The network supports 802.1X network authentication.
The Ethernet connection profile exists in NetworkManager and has a valid IP configuration.
The following files required for TLS authentication exist on the client:
- The client key stored is in the /etc/pki/tls/private/client.key file, and the file is owned and only readable by the root user.
- The client certificate is stored in the /etc/pki/tls/certs/client.crt file.
- The Certificate Authority (CA) certificate is stored in the /etc/pki/tls/certs/ca.crt file.
The wpa_supplicant package is installed.

Procedure

Set the Extensible Authentication Protocol (EAP) to tls and the paths to the client certificate and key file:
```
# nmcli connection modify 
enp1s0
 802-1x.eap tls 802-1x.client-cert /etc/pki/tls/certs/client.crt 802-1x.private-key /etc/pki/tls/certs/certs/client.key
```
Note that you must set the 802-1x.eap, 802-1x.client-cert, and 802-1x.private-key parameters in a single command.

Set the path to the CA certificate:

nmcli connection modify

enp1s0

802-1x.ca-cert /etc/pki/tls/certs/ca.crt

Set the identity of the user used in the certificate:

# nmcli connection modify 
enp1s0
 802-1x.identity [email protected]

Optionally, store the password in the configuration:
```
# nmcli connection modify 
enp1s0
 802-1x.private-key-password password
```
Important

By default, NetworkManager stores the password in clear text in the /etc/sysconfig/network-scripts/keys-connection_name file, that is readable only by the root user. However, clear text passwords in a configuration file can be a security risk.

To increase the security, set the 802-1x.password-flags parameter to 0x1. With this setting, on servers with the GNOME desktop environment or the nm-applet running, NetworkManager retrieves the password from these services. In other cases, NetworkManager prompts for the password.
Activate the connection profile:
```
# nmcli connection up 
enp1s0
```

Verification steps

Access resources on the network that require network authentication.

Additional resources

Configuring an Ethernet connection
nm-settings(5) man page
nmcli(1) man page

18.2. Configuring a static Ethernet connection with 802.1X network authentication using nmstatectl

Using the nmstate utility, you can create an Ethernet connection that uses the 802.1X standard to authenticate the client. For example, add an Ethernet connection for the enp1s0 interface with the following settings:

A static IPv4 address – 192.0.2.1 with a /24 subnet mask
A static IPv6 address – 2001:db8:1::1 with a /64 subnet mask
An IPv4 default gateway – 192.0.2.254
An IPv6 default gateway – 2001:db8:1::fffe
An IPv4 DNS server – 192.0.2.200
An IPv6 DNS server – 2001:db8:1::ffbb
A DNS search domain – example.com
802.1X network authentication using the TLS Extensible Authentication Protocol (EAP)

Note

The nmstate library only supports the TLS EAP method.

Prerequisites

The network supports 802.1X network authentication.
The managed node uses NetworkManager.
The following files required for TLS authentication exist on the client:
- The client key stored is in the /etc/pki/tls/private/client.key file, and the file is owned and only readable by the root user.
- The client certificate is stored in the /etc/pki/tls/certs/client.crt file.
- The Certificate Authority (CA) certificate is stored in the /etc/pki/tls/certs/ca.crt file.

Procedure

Create a YAML file, for example ~/create-ethernet-profile.yml, with the following contents:

--- interfaces: - name:

enp1s0

type:

ethernet

state:

ipv4: enabled:

true

address: - ip:

192.0.2.1

prefix-length:

dhcp:

false

ipv6: enabled:

true

address: - ip:

2001:db8:1::1

prefix-length:

autoconf:

false

dhcp:

false

802.1x: ca-cert:

/etc/pki/tls/certs/ca.crt

client-cert:

/etc/pki/tls/certs/client.crt

eap-methods: - tls identity:

client.example.org

private-key:

/etc/pki/tls/private/client.key

private-key-password:

password

routes: config: - destination:

0.0.0.0/0

next-hop-address:

192.0.2.254

next-hop-interface:

enp1s0

- destination:

::/0

next-hop-address:

2001:db8:1::fffe

next-hop-interface:

enp1s0

dns-resolver: config: search: -

example.com

server: -

192.0.2.200

2001:db8:1::ffbb

Apply the settings to the system:

nmstatectl apply ~/create-ethernet-profile.yml

Verification

Access resources on the network that require network authentication.

18.3. Configuring a static Ethernet connection with 802.1X network authentication using RHEL System Roles

Using the network RHEL System Role, you can automate the creation of an Ethernet connection that uses the 802.1X standard to authenticate the client. For example, remotely add an Ethernet connection for the enp1s0 interface with the following settings by running an Ansible playbook:

A static IPv4 address – 192.0.2.1 with a /24 subnet mask
A static IPv6 address – 2001:db8:1::1 with a /64 subnet mask
An IPv4 default gateway – 192.0.2.254
An IPv6 default gateway – 2001:db8:1::fffe
An IPv4 DNS server – 192.0.2.200
An IPv6 DNS server – 2001:db8:1::ffbb
A DNS search domain – example.com
802.1X network authentication using the TLS Extensible Authentication Protocol (EAP)

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on them.
The hosts or host groups on which you want to run this playbook are listed in the Ansible inventory file.

The network supports 802.1X network authentication.
The managed nodes uses NetworkManager.
The following files required for TLS authentication exist on the control node:
- The client key is stored in the /srv/data/client.key file.
- The client certificate is stored in the /srv/data/client.crt file.
- The Certificate Authority (CA) certificate is stored in the /srv/data/ca.crt file.

Procedure

Create a playbook file, for example ~/enable-802.1x.yml, with the following content:

--- - name: Configure an Ethernet connection with 802.1X authentication hosts:

managed-node-01.example.com

tasks: - name: Copy client key for 802.1X authentication copy: src: "/srv/data/client.key" dest: "/etc/pki/tls/private/client.key" mode: 0600 - name: Copy client certificate for 802.1X authentication copy: src: "/srv/data/client.crt" dest: "/etc/pki/tls/certs/client.crt" - name: Copy CA certificate for 802.1X authentication copy: src: "/srv/data/ca.crt" dest: "/etc/pki/ca-trust/source/anchors/ca.crt" - include_role: name: rhel-system-roles.network vars: network_connections: - name: enp1s0 type: ethernet autoconnect: yes ip: address: - 192.0.2.1/24 - 2001:db8:1::1/64 gateway4: 192.0.2.254 gateway6: 2001:db8:1::fffe dns: - 192.0.2.200 - 2001:db8:1::ffbb dns_search: - example.com ieee802_1x: identity:

user_name

eap: tls private_key: "/etc/pki/tls/private/client.key" private_key_password: "password" client_cert: "/etc/pki/tls/certs/client.crt" ca_cert: "/etc/pki/ca-trust/source/anchors/ca.crt" domain_suffix_match:

example.com

state: up

Run the playbook:
```
# ansible-playbook 
~/enable-802.1x.yml
```

Additional resources

/usr/share/ansible/roles/rhel-system-roles.network/README.md file

Chapter 19. Managing the default gateway setting

The default gateway is a router that forwards network packets when no other route matches the destination of a packet. In a local network, the default gateway is typically the host that is one hop closer to the internet.

19.1. Setting the default gateway on an existing connection using nmcli

In most situations, administrators set the default gateway when they create a connection as explained in, for example, Configuring a static Ethernet connection using nmcli.

In most situations, administrators set the default gateway when they create a connection. However, you can also set or update the default gateway setting on a previously created connection using the nmcli utility.

Prerequisites

At least one static IP address must be configured on the connection on which the default gateway will be set.
If the user is logged in on a physical console, user permissions are sufficient. Otherwise, user must have root permissions.

Procedure

Set the IP address of the default gateway.

For example, to set the IPv4 address of the default gateway on the example connection to 192.0.2.1:
```
# nmcli connection modify 
example
 ipv4.gateway "192.0.2.1"
```
For example, to set the IPv6 address of the default gateway on the example connection to 2001:db8:1::1:
```
# nmcli connection modify 
example
 ipv6.gateway "2001:db8:1::1"
```
Restart the network connection for changes to take effect. For example, to restart the example connection using the command line:
```
# nmcli connection up 
example
```
Warning

All connections currently using this network connection are temporarily interrupted during the restart.

Optionally, verify that the route is active.

To display the IPv4 default gateway:

# ip -4 route
default via 192.0.2.1 dev example
 proto static metric 100

To display the IPv6 default gateway:

# ip -6 route
default via 2001:db8:1::1 dev example
 proto static metric 100 pref medium

Additional resources

Configuring a static Ethernet connection using nmcli

19.2. Setting the default gateway on an existing connection using the nmcli interactive mode

In most situations, administrators set the default gateway when they create a connection as explained in, for example, Configuring a dynamic Ethernet connection using the nmcli interactive editor.

Prerequisites

At least one static IP address must be configured on the connection on which the default gateway will be set.
If the user is logged in on a physical console, user permissions are sufficient. Otherwise, the user must have root permissions.

Procedure

Open the nmcli interactive mode for the required connection. For example, to open the nmcli interactive mode for the example connection:
```
# nmcli connection edit 
example
```
Set the default gateway.

For example, to set the IPv4 address of the default gateway on the example connection to 192.0.2.1:
```
nmcli> set ipv4.gateway 192.0.2.1
```
For example, to set the IPv6 address of the default gateway on the example connection to 2001:db8:1::1:
```
nmcli> set ipv6.gateway 2001:db8:1::1
```

Optionally, verify that the default gateway was set correctly:

nmcli>

print

... ipv4.gateway: 192.0.2.1 ... ipv6.gateway: 2001:db8:1::1 ...

Save the configuration:
```
nmcli> save persistent
```
Restart the network connection for changes to take effect:
```
nmcli> activate 
example
```
Warning

All connections currently using this network connection are temporarily interrupted during the restart.
Leave the nmcli interactive mode:
```
nmcli> quit
```

Optionally, verify that the route is active.

To display the IPv4 default gateway:

# ip -4 route
default via 192.0.2.1 dev example
 proto static metric 100

To display the IPv6 default gateway:

# ip -6 route
default via 2001:db8:1::1 dev example
 proto static metric 100 pref medium

Additional resources

Configuring a static Ethernet connection using the nmcli interactive editor

19.3. Setting the default gateway on an existing connection using nm-connection-editor

Prerequisites

At least one static IP address must be configured on the connection on which the default gateway will be set.

Procedure

Open a terminal, and enter nm-connection-editor:
```
# nm-connection-editor
```
Select the connection to modify, and click the gear wheel icon to edit the existing connection.
Set the IPv4 default gateway. For example, to set the IPv4 address of the default gateway on the connection to 192.0.2.1:
1. Open the IPv4 Settings tab.
2. Enter the address in the gateway field next to the IP range the gateway’s address is within:
Set the IPv6 default gateway. For example, to set the IPv6 address of the default gateway on the connection to 2001:db8:1::1:
1. Open the IPv6 tab.
2. Enter the address in the gateway field next to the IP range the gateway’s address is within:
Click

OK

.
Click

Save

.
Restart the network connection for changes to take effect. For example, to restart the example connection using the command line:
```
# nmcli connection up 
example
```
Warning

All connections currently using this network connection are temporarily interrupted during the restart.

Optionally, verify that the route is active.

To display the IPv4 default gateway:

# ip -4 route
default via 192.0.2.1 dev example
 proto static metric 100

To display the IPv6 default gateway:

# ip -6 route
default via 2001:db8:1::1 dev example
 proto static metric 100 pref medium

Additional resources

Configuring an Ethernet connection using nm-connection-editor

19.4. Setting the default gateway on an existing connection using control-center

Prerequisites

At least one static IP address must be configured on the connection on which the default gateway will be set.
The network configuration of the connection is open in the control-center application.

Procedure

Set the IPv4 default gateway. For example, to set the IPv4 address of the default gateway on the connection to 192.0.2.1:
1. Open the IPv4 tab.
2. Enter the address in the gateway field next to the IP range the gateway’s address is within:
Set the IPv6 default gateway. For example, to set the IPv6 address of the default gateway on the connection to 2001:db8:1::1:
1. Open the IPv6 tab.
2. Enter the address in the gateway field next to the IP range the gateway’s address is within:
Click

Apply

.
Back in the Network window, disable and re-enable the connection by switching the button for the connection to Off and back to On for changes to take effect.

Warning

All connections currently using this network connection are temporarily interrupted during the restart.

Optionally, verify that the route is active.

To display the IPv4 default gateway:

$ ip -4 route
default via 192.0.2.1 dev example
 proto static metric 100

To display the IPv6 default gateway:

$ ip -6 route
default via 2001:db8:1::1 dev example
 proto static metric 100 pref medium

Additional resources

Configuring an Ethernet connection using control-center

19.5. Setting the default gateway on an existing connection using nmstatectl

In most situations, administrators set the default gateway when they create a connection. However, you can also set or update the default gateway setting of a network connection using the nmstatectl utility.

Prerequisites

At least one static IP address must be configured on the connection on which the default gateway will be set.
The enp1s0 interface is configured, and the IP address of the default gateway is within the subnet of the IP configuration of this interface.
The nmstate package is installed.

Procedure

Create a YAML file, for example ~/set-default-gateway.yml, with the following contents:

---
routes:
  config:
  - destination: 0.0.0.0/0
    next-hop-address: 192.0.2.1
    next-hop-interface: enp1s0

Apply the settings to the system:

nmstatectl apply ~/set-default-gateway.yml

Additional resources

nmstatectl(8) man page
/usr/share/doc/nmstate/examples/ directory

19.6. Setting the default gateway on an existing connection using RHEL System Roles

You can use the network RHEL System Role to set the default gateway.

Important

When you run a play that uses the network RHEL System Role, the system role overrides an existing connection profile with the same name if the value of settings does not match the ones specified in the play. Therefore, always specify the whole configuration of the network connection profile in the play, even if, for example, the IP configuration already exists. Otherwise, the role resets these values to their defaults.

Depending on whether it already exists, the procedure creates or updates the enp1s0 connection profile with the following settings:

A static IPv4 address – 198.51.100.20 with a /24 subnet mask
A static IPv6 address – 2001:db8:1::1 with a /64 subnet mask
An IPv4 default gateway – 198.51.100.254
An IPv6 default gateway – 2001:db8:1::fffe
An IPv4 DNS server – 198.51.100.200
An IPv6 DNS server – 2001:db8:1::ffbb
A DNS search domain – example.com

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on them.
The hosts or host groups on which you want to run this playbook are listed in the Ansible inventory file.

Procedure

Create a playbook file, for example ~/ethernet-connection.yml, with the following content:

---
- name: Configure the network
  hosts: managed-node-01.example.com
  tasks:
  - name: Configure an Ethernet connection with static IP and default gateway
    include_role:
      name: rhel-system-roles.network

    vars:
      network_connections:
        - name: enp1s0
          type: ethernet
          autoconnect: yes
          ip:
            address:
              - 198.51.100.20/24
              - 2001:db8:1::1/64
            gateway4: 198.51.100.254
            gateway6: 2001:db8:1::fffe
            dns:
              - 198.51.100.200
              - 2001:db8:1::ffbb
            dns_search:
              - example.com
          state: up

Run the playbook:

ansible-playbook

~/ethernet-connection.yml

Additional resources

/usr/share/ansible/roles/rhel-system-roles.network/README.md file

19.7. Setting the default gateway on an existing connection when using the legacy network scripts

Prerequisites

The NetworkManager package is not installed, or the NetworkManager service is disabled.
The network-scripts package is installed.

Procedure

Set the GATEWAY parameter in the /etc/sysconfig/network-scripts/ifcfg-enp1s0 file to 192.0.2.1:
```
GATEWAY=192.0.2.1
```
Add the default entry in the /etc/sysconfig/network-scripts/route-enp0s1 file:
```
default via 192.0.2.1
```
Restart the network:
```
# systemctl restart network
```

19.8. How NetworkManager manages multiple default gateways

In certain situations, for example for fallback reasons, you set multiple default gateways on a host. However, to avoid asynchronous routing issues, each default gateway of the same protocol requires a separate metric value. Note that RHEL only uses the connection to the default gateway that has the lowest metric set.

You can set the metric for both the IPv4 and IPv6 gateway of a connection using the following command:

nmcli connection modify

connection-name

ipv4.route-metric
value
ipv6.route-metric
value

Important

Do not set the same metric value for the same protocol in multiple connection profiles to avoid routing issues.

If you set a default gateway without a metric value, NetworkManager automatically sets the metric value based on the interface type. For that, NetworkManager assigns the default value of this network type to the first connection that is activated, and sets an incremented value to each other connection of the same type in the order they are activated. For example, if two Ethernet connections with a default gateway exist, NetworkManager sets a metric of 100 on the route to the default gateway of the connection that you activate first. For the second connection, NetworkManager sets 101.

The following is an overview of frequently-used network types and their default metrics:

Connection typeDefault metric value

VPN

Ethernet

100

MACsec

125

InfiniBand

150

Bond

300

Team

350

VLAN

400

Bridge

425

TUN

450

Wi-Fi

600

IP tunnel

675

Additional resources

Configuring policy-based routing to define alternative routes
Getting started with Multipath TCP

19.9. Configuring NetworkManager to avoid using a specific profile to provide a default gateway

You can configure that NetworkManager never uses a specific profile to provide the default gateway. Follow this procedure for connection profiles that are not connected to the default gateway.

Prerequisites

The NetworkManager connection profile for the connection that is not connected to the default gateway exists.

Procedure

If the connection uses a dynamic IP configuration, configure that NetworkManager does not use the connection as the default route for IPv4 and IPv6 connections:
```
# nmcli connection modify 
connection_name
 ipv4.never-default yes ipv6.never-default yes
```
Note that setting ipv4.never-default and ipv6.never-default to yes, automatically removes the default gateway’s IP address for the corresponding protocol from the connection profile.
Activate the connection:
```
# nmcli connection up 
connection_name
```

Verification steps

Use the ip -4 route and ip -6 route commands to verify that RHEL does not use the network interface for the default route for the IPv4 and IPv6 protocol.

19.10. Fixing unexpected routing behavior due to multiple default gateways

There are only a few scenarios, such as when using multipath TCP, in which you require multiple default gateways on a host. In most cases, you configure only a single default gateway to avoid unexpected routing behavior or asynchronous routing issues.

Note

To route traffic to different internet providers, use policy-based routing instead of multiple default gateways.

Prerequisites

The host uses NetworkManager to manage network connections, which is the default.
The host has multiple network interfaces.
The host has multiple default gateways configured.

Procedure

Display the routing table:

For IPv4, enter:

# ip -4 route
default via 192.0.2.1 dev enp1s0 proto static metric 101
default via 198.51.100.1 dev enp7s0 proto static metric 102
...

For IPv6, enter:

# ip -6 route
default via 2001:db8:1::1 dev enp1s0 proto static metric 101 pref medium
default via 2001:db8:2::1 dev enp7s0 proto static metric 102 pref medium
...

Entries starting with default indicate a default route. Note the interface names of these entries displayed next to dev.

Use the following commands to display the NetworkManager connections that use the interfaces you identified in the previous step:
```
# nmcli -f GENERAL.CONNECTION,IP4.GATEWAY,IP6.GATEWAY device show enp1s0
GENERAL.CONNECTION:      Corporate-LAN
IP4.GATEWAY:             192.168.122.1
IP6.GATEWAY:             2001:db8:1::1

# nmcli -f GENERAL.CONNECTION,IP4.GATEWAY,IP6.GATEWAY device show enp7s0
GENERAL.CONNECTION:      Internet-Provider
IP4.GATEWAY:             198.51.100.1
IP6.GATEWAY:             2001:db8:2::1
```
In these examples, the profiles named Corporate-LAN and Internet-Provider have the default gateways set. Because, in a local network, the default gateway is typically the host that is one hop closer to the internet, the rest of this procedure assumes that the default gateways in the Corporate-LAN are incorrect.
Configure that NetworkManager does not use the Corporate-LAN connection as the default route for IPv4 and IPv6 connections:
```
# nmcli connection modify Corporate-LAN ipv4.never-default yes ipv6.never-default yes
```
Note that setting ipv4.never-default and ipv6.never-default to yes, automatically removes the default gateway’s IP address for the corresponding protocol from the connection profile.
Activate the Corporate-LAN connection:
```
# nmcli connection up Corporate-LAN
```

Verification steps

Display the IPv4 and IPv6 routing tables and verify that only one default gateway is available for each protocol:

For IPv4, enter:

# ip -4 route
default via 192.0.2.1 dev enp1s0 proto static metric 101
...

For IPv6, enter:

# ip -6 route
default via 2001:db8:1::1 dev enp1s0 proto static metric 101 pref medium
...

Additional resources

Configuring policy-based routing to define alternative routes
Getting started with Multipath TCP

Chapter 20. Configuring static routes

Routing ensures that you can send and receive traffic between mutually-connected networks. In larger environments, administrators typically configure services so that routers can dynamically learn about other routers. In smaller environments, administrators often configure static routes to ensure that traffic can reach from one network to the next.

You need static routes to achieve a functioning communication among multiple networks if all of these conditions apply:

The traffic has to pass multiple networks.
The exclusive traffic flow through the default gateways is not sufficient.

Section 20.1, “Example of a network that requires static routes” describes scenarios and how the traffic flows between different networks when you do not configure static routes.

20.1. Example of a network that requires static routes

You require static routes in this example because not all IP networks are directly connected through one router. Without the static routes, some networks cannot communicate with each other. Additionally, traffic from some networks flows only in one direction.

Note

The network topology in this example is artificial and only used to explain the concept of static routing. It is not a recommended topology in production environments.

For a functioning communication among all networks in this example, configure a static route to Raleigh (198.51.100.0/24) with next the hop Router 2 (203.0.113.10). The IP address of the next hop is the one of Router 2 in the data center network (203.0.113.0/24).

You can configure the static route as follows:

For a simplified configuration, set this static route only on Router 1. However, this increases the traffic on Router 1 because hosts from the data center (203.0.113.0/24) send traffic to Raleigh (198.51.100.0/24) always through Router 1 to Router 2.
For a more complex configuration, configure this static route on all hosts in the data center (203.0.113.0/24). All hosts in this subnet then send traffic directly to Router 2 (203.0.113.10) that is closer to Raleigh (198.51.100.0/24).

For more details between which networks traffic flows or not, see the explanations below the diagram.

routing example

In case that the required static routes are not configured, the following are the situations in which the communication works and when it does not:

Hosts in the Berlin network (192.0.2.0/24):
- Can communicate with other hosts in the same subnet because they are directly connected.
- Can communicate with the Internet because Router 1 is in the Berlin network (192.0.2.0/24) and has a default gateway, which leads to the Internet.
- Can communicate with the data center network (203.0.113.0/24) because Router 1 has interfaces in both the Berlin (192.0.2.0/24) and the data center (203.0.113.0/24) networks.
- Cannot communicate with the Raleigh network (198.51.100.0/24) because Router 1 has no interface in this network. Therefore, Router 1 sends the traffic to its own default gateway (Internet).
Hosts in the data center network (203.0.113.0/24):
- Can communicate with other hosts in the same subnet because they are directly connected.
- Can communicate with the Internet because they have their default gateway set to Router 1, and Router 1 has interfaces in both networks, the data center (203.0.113.0/24) and to the Internet.
- Can communicate with the Berlin network (192.0.2.0/24) because they have their default gateway set to Router 1, and Router 1 has interfaces in both the data center (203.0.113.0/24) and the Berlin (192.0.2.0/24) networks.
- Cannot communicate with the Raleigh network (198.51.100.0/24) because the data center network has no interface in this network. Therefore, hosts in the data center (203.0.113.0/24) send traffic to their default gateway (Router 1). Router 1 also has no interface in the Raleigh network (198.51.100.0/24) and, as a result, Router 1 sends this traffic to its own default gateway (Internet).
Hosts in the Raleigh network (198.51.100.0/24):
- Can communicate with other hosts in the same subnet because they are directly connected.
- Cannot communicate with hosts on the Internet. Router 2 sends the traffic to Router 1 because of the default gateway settings. The actual behavior of Router 1 depends on the reverse path filter (rp_filter) system control (sysctl) setting. By default on RHEL, Router 1 drops the outgoing traffic instead of routing it to the Internet. However, regardless of the configured behavior, communication is not possible without the static route.
- Cannot communicate with the data center network (203.0.113.0/24). The outgoing traffic reaches the destination through Router 2 because of the default gateway setting. However, replies to packets do not reach the sender because hosts in the data center network (203.0.113.0/24) send replies to their default gateway (Router 1). Router 1 then sends the traffic to the Internet.
- Cannot communicate with the Berlin network (192.0.2.0/24). Router 2 sends the traffic to Router 1 because of the default gateway settings. The actual behavior of Router 1 depends on the rp_filter sysctl setting. By default on RHEL, Router 1 drops the outgoing traffic instead of sending it to the Berlin network (192.0.2.0/24). However, regardless of the configured behavior, communication is not possible without the static route.

Note

In addition to configuring the static routes, you must enable IP forwarding on both routers.

Additional resources

Why can’t a server be pinged if net.ipv4.conf.all.rp_filter is set on the server?
Enabling IP forwarding

20.2. How to use the nmcli command to configure a static route

To configure a static route, use the nmcli utility with the following syntax:

$ nmcli connection modify 
connection_name
 ipv4.routes "ip
[/prefix
] [next_hop
] [metric
] [attribute
=value
] [attribute
=value
] ..."

The command supports the following route attributes:

cwnd= n
: Sets the congestion window (CWND) size, defined in number of packets.
lock-cwnd=true|false: Defines whether or not the kernel can update the CWND value.
lock-mtu=true|false: Defines whether or not the kernel can update the MTU to path MTU discovery.
lock-window=true|false: Defines whether or not the kernel can update the maximum window size for TCP packets.
mtu= n
: Sets the maximum transfer unit (MTU) to use along the path to the destination.
onlink=true|false: Defines whether the next hop is directly attached to this link even if it does not match any interface prefix.
scope= n
: For an IPv4 route, this attribute sets the scope of the destinations covered by the route prefix. Set the value as an integer (0-255).
src= address
: Sets the source address to prefer when sending traffic to the destinations covered by the route prefix.
table= table_id
: Sets the ID of the table the route should be added to. If you omit this parameter, NetworkManager uses the main table.
tos= n
: Sets the type of service (TOS) key. Set the value as an integer (0-255).
type= value
: Sets the route type. NetworkManager supports the unicast, local, blackhole, unreachable, prohibit, and throw route types. The default is unicast.
window= n
: Sets the maximal window size for TCP to advertise to these destinations, measured in bytes.

If you use the ipv4.routes sub-command, nmcli overrides all current settings of this parameter.

To add a route:

nmcli connection modify

connection_name

+ipv4.routes "..."

Similarly, to remove a specific route:

nmcli connection modify

connection_name

-ipv4.routes "..."

20.3. Configuring a static route using an nmcli command

You can add a static route to an existing NetworkManager connection profile using the nmcli connection modify command.

The procedure below configures the following routes:

An IPv4 route to the remote 198.51.100.0/24 network. The corresponding gateway with the IP address 192.0.2.10 is reachable through the example connection.
An IPv6 route to the remote 2001:db8:2::/64 network. The corresponding gateway with the IP address 2001:db8:1::10 is reachable through the example connection.

Prerequisites

The example connection profile exists and it configures this host to be in the same IP subnet as the gateways.

Procedure

Add the static IPv4 route to the example connection profile:
```
# nmcli connection modify 
example
 +ipv4.routes "198.51.100.0/24 192.0.2.10
"
```
To set multiple routes in one step, pass the individual routes comma-separated to the command. For example, to add a route to the 198.51.100.0/24 and 203.0.113.0/24 networks, both routed through the 192.0.2.10 gateway, enter:
```
# nmcli connection modify 
example
 +ipv4.routes "198.51.100.0/24 192.0.2.10
, 203.0.113.0/24 192.0.2.10
"
```

Add the static IPv6 route to the example connection profile:

nmcli connection modify

example

+ipv6.routes "
2001:db8:2::/64 2001:db8:1::10
"

Re-activate the connection:
```
# nmcli connection up 
example
```

Verification

Display the IPv4 routes:

ip -4 route

...

198.51.100.0/24

via

192.0.2.10

dev

enp1s0

Display the IPv6 routes:

ip -6 route

...

2001:db8:2::/64

via

2001:db8:1::10

dev

enp1s0

metric

1024

pref

medium

Additional resources

nmcli(1) man page
nm-settings-nmcli(5) man page

20.4. Configuring a static route using nmtui

The nmtui application provides a text-based user interface for NetworkManager. You can use nmtui to configure static routes on a host without a graphical interface.

For example, the procedure below adds a route to the 192.0.2.0/24 network that uses the gateway running on 198.51.100.1, which is reachable through an existing connection profile.

Note

In nmtui:

Navigate by using the cursor keys.
Press a button by selecting it and hitting

Enter

.
Select and deselect checkboxes by using

Space

.

Prerequisites

The network is configured.
The gateway for the static route must be directly reachable on the interface.
If the user is logged in on a physical console, user permissions are sufficient. Otherwise, the command requires root permissions.

Procedure

Start nmtui:
```
# nmtui
```
Select Edit a connection, and press

Enter

.
Select the connection profile through which you can reach the next hop to the destination network, and press

Enter

.
Depending on whether it is an IPv4 or IPv6 route, press the Show button next to the protocol’s configuration area.
Press the Edit button next to Routing. This opens a new window where you configure static routes:
1. Press the Add button and fill in:
  - The destination network, including the prefix in Classless Inter-Domain Routing (CIDR) format
  - The IP address of the next hop
  - A metric value, if you add multiple routes to the same network and want to prioritize the routes by efficiency
2. Repeat the previous step for every route you want to add and that is reachable through this connection profile.
3. Press the OK button to return to the window with the connection settings.
  
  Figure 20.1. Example of a static route without metric
Press the OK button to return to the nmtui main menu.
Select Activate a connection and press

Enter

.
Select the connection profile that you edited, and press Enter twice to deactivate and activate it again.

Important

Skip this step if you run nmtui over a remote connection, such as SSH, that uses the connection profile you want to reactivate. In this case, if you would deactivate it in nmtui, the connection is terminated and, consequently, you cannot activate it again. To avoid this problem, use the nmcli connection connection_profile_name up command to reactivate the connection in the mentioned scenario.
Press the Back button to return to the main menu.
Select Quit, and press

Enter

to close the nmtui application.

Verification

Verify that the route is active:

$ ip route
...
192.0.2.0/24 via 198.51.100.1 dev example
 proto static metric 100

20.5. Configuring a static route using control-center

You can use control-center in GNOME to add a static route to the configuration of a network connection.

The procedure below configures the following routes:

An IPv4 route to the remote 198.51.100.0/24 network. The corresponding gateway has the IP address 192.0.2.10.
An IPv6 route to the remote 2001:db8:2::/64 network. The corresponding gateway has the IP address 2001:db8:1::10.

Prerequisites

The network is configured.
This host is in the same IP subnet as the gateways.
The network configuration of the connection is opened in the control-center application. See Configuring an Ethernet connection using nm-connection-editor.

Procedure

On the IPv4 tab:
1. Optional: Disable automatic routes by clicking the
  
  On
  
  button in the Routes section of the IPv4 tab to use only static routes. If automatic routes are enabled, Red Hat Enterprise Linux uses static routes and routes received from a DHCP server.
2. Enter the address, netmask, gateway, and optionally a metric value of the IPv4 route:
On the IPv6 tab:
1. Optional: Disable automatic routes by clicking the
  
  On
  
  button i the Routes section of the IPv4 tab to use only static routes.
2. Enter the address, netmask, gateway, and optionally a metric value of the IPv6 route:
Click

Apply

.
Back in the Network window, disable and re-enable the connection by switching the button for the connection to Off and back to On for changes to take effect.

Warning

Restarting the connection briefly disrupts connectivity on that interface.

Verification

Display the IPv4 routes:

ip -4 route

...

198.51.100.0/24

via

192.0.2.10

dev

enp1s0

Display the IPv6 routes:

ip -6 route

...

2001:db8:2::/64

via

2001:db8:1::10

dev

enp1s0

metric

1024

pref

medium

20.6. Configuring a static route using nm-connection-editor

You can use the nm-connection-editor application to add a static route to the configuration of a network connection.

The procedure below configures the following routes:

An IPv4 route to the remote 198.51.100.0/24 network. The corresponding gateway with the IP address 192.0.2.10 is reachable through the example connection.
An IPv6 route to the remote 2001:db8:2::/64 network. The corresponding gateway with the IP address 2001:db8:1::10 is reachable through the example connection.

Prerequisites

The network is configured.
This host is in the same IP subnet as the gateways.

Procedure

Open a terminal, and enter nm-connection-editor:
```
$ nm-connection-editor
```
Select the example connection profile, and click the gear wheel icon to edit the existing connection.
On the IPv4 Settings tab:
1. Click the
  
  Routes
  
  button.
2. Click the Add button and enter the address, netmask, gateway, and optionally a metric value.
3. Click
  
  OK
  
  .
On the IPv6 Settings tab:
1. Click the
  
  Routes
  
  button.
2. Click the Add button and enter the address, netmask, gateway, and optionally a metric value.
3. Click
  
  OK
  
  .
Click

Save

.
Restart the network connection for changes to take effect. For example, to restart the example connection using the command line:
```
# nmcli connection up 
example
```

Verification

Display the IPv4 routes:

ip -4 route

...

198.51.100.0/24

via

192.0.2.10

dev

enp1s0

Display the IPv6 routes:

ip -6 route

...

2001:db8:2::/64

via

2001:db8:1::10

dev

enp1s0

metric

1024

pref

medium

20.7. Configuring a static route using the nmcli interactive mode

You can use the interactive mode of the nmcli utility to add a static route to the configuration of a network connection.

The procedure below configures the following routes:

An IPv4 route to the remote 198.51.100.0/24 network. The corresponding gateway with the IP address 192.0.2.10 is reachable through the example connection.
An IPv6 route to the remote 2001:db8:2::/64 network. The corresponding gateway with the IP address 2001:db8:1::10 is reachable through the example connection.

Prerequisites

The example connection profile exists and it configures this host to be in the same IP subnet as the gateways.

Procedure

Open the nmcli interactive mode for the example connection:
```
# nmcli connection edit 
example
```

Add the static IPv4 route:

nmcli>

set ipv4.routes

198.51.100.0/24 192.0.2.10

Add the static IPv6 route:

nmcli>

set ipv6.routes

2001:db8:2::/64 2001:db8:1::10

Optionally, verify that the routes were added correctly to the configuration:
```
nmcli> print
...
ipv4.routes:    { ip = 198.51.100.0/24
, nh = 192.0.2.10 }
...
ipv6.routes:    { ip = 2001:db8:2::/64
, nh = 2001:db8:1::10 }
...
```
The ip attribute displays the network to route and the nh attribute the gateway (next hop).
Save the configuration:
```
nmcli> save persistent
```
Restart the network connection:
```
nmcli> activate 
example
```
Leave the nmcli interactive mode:
```
nmcli> quit
```

Verification

Display the IPv4 routes:

ip -4 route

...

198.51.100.0/24

via

192.0.2.10

dev

enp1s0

Display the IPv6 routes:

ip -6 route

...

2001:db8:2::/64

via

2001:db8:1::10

dev

enp1s0

metric

1024

pref

medium

Additional resources

nmcli(1) man page
nm-settings-nmcli(5) man page

20.8. Configuring a static route using nmstatectl

You can add a static route to the configuration of a network connection using the nmstatectl utility.

The procedure below configures the following routes:

An IPv4 route to the remote 198.51.100.0/24 network. The corresponding gateway with the IP address 192.0.2.10 is reachable through the enp1s0 interface.
An IPv6 route to the remote 2001:db8:2::/64 network. The corresponding gateway with the IP address 2001:db8:1::10 is reachable through the enp1s0 interface.

Prerequisites

The enp1s0 network interface is configured and is in the same IP subnet as the gateways.
The nmstate package is installed.

Procedure

Create a YAML file, for example ~/add-static-route-to-enp1s0.yml, with the following contents:

---

routes:

config:

- destination:

198.51.100.0/24

next-hop-address:

192.0.2.10

next-hop-interface:

enp1s0

- destination:

2001:db8:2::/64

next-hop-address:

2001:db8:1::10

next-hop-interface:

enp1s0

Apply the settings to the system:

nmstatectl apply

~/add-static-route-to-enp1s0.yml

Verification

Display the IPv4 routes:

ip -4 route

...

198.51.100.0/24

via

192.0.2.10

dev

enp1s0

Display the IPv6 routes:

ip -6 route

...

2001:db8:2::/64

via

2001:db8:1::10

dev

enp1s0

metric

1024

pref

medium

Additional resources

nmstatectl(8) man page
/usr/share/doc/nmstate/examples/ directory

20.9. Configuring a static route using RHEL System Roles

You can use the network RHEL System Role to configure static routes.

Important

Depending on whether it already exists, the procedure creates or updates the enp7s0 connection profile with the following settings:

A static IPv4 address – 192.0.2.1 with a /24 subnet mask
A static IPv6 address – 2001:db8:1::1 with a /64 subnet mask
An IPv4 default gateway – 192.0.2.254
An IPv6 default gateway – 2001:db8:1::fffe
An IPv4 DNS server – 192.0.2.200
An IPv6 DNS server – 2001:db8:1::ffbb
A DNS search domain – example.com
Static routes:
- 198.51.100.0/24 with gateway 192.0.2.10
- 2001:db8:2::/64 with gateway 2001:db8:1::10

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on them.
The hosts or host groups on which you to want run this playbook are listed in the Ansible inventory file.

Procedure

Create a playbook file, for example ~/add-static-routes.yml, with the following content:

---
- name: Configure the network
  hosts: managed-node-01.example.com
  tasks:
  - name: Configure an Ethernet connection with static IP and additional routes
    include_role:
      name: rhel-system-roles.network

    vars:
      network_connections:
        - name: enp7s0
          type: ethernet
          autoconnect: yes
          ip:
            address:
              - 192.0.2.1/24
              - 2001:db8:1::1/64
            gateway4: 192.0.2.254
            gateway6: 2001:db8:1::fffe
            dns:
              - 192.0.2.200
              - 2001:db8:1::ffbb
            dns_search:
              - example.com
            route:
              - network: 198.51.100.0
                prefix: 24
                gateway: 192.0.2.10
              - network: 2001:db8:2::
                prefix: 64
                gateway: 2001:db8:1::10
          state: up

Run the playbook:

ansible-playbook

~/add-static-routes.yml

Verification steps

On the managed nodes:

Display the IPv4 routes:

ip -4 route

...

198.51.100.0/24

via

192.0.2.10

dev

enp7s0

Display the IPv6 routes:

ip -6 route

...

2001:db8:2::/64

via

2001:db8:1::10

dev

enp7s0

metric

1024

pref

medium

Additional resources

/usr/share/ansible/roles/rhel-system-roles.network/README.md file

20.10. Creating static routes configuration files in key-value format when using the legacy network scripts

The legacy network scripts support setting statics routes in key-value format.

The procedure below configures an IPv4 route to the remote 198.51.100.0/24 network. The corresponding gateway with the IP address 192.0.2.10 is reachable through the enp1s0 interface.

Note

The legacy network scripts support the key-value format only for static IPv4 routes. For IPv6 routes, use the ip-command format. See Creating static routes configuration files in ip-command format when using the legacy network scripts.

Prerequisites

The gateways for the static route must be directly reachable on the interface.
The NetworkManager package is not installed, or the NetworkManager service is disabled.
The network-scripts package is installed.
The network service is enabled.

Procedure

Add the static IPv4 route to the /etc/sysconfig/network-scripts/route-enp0s1 file:
```
ADDRESS0=198.51.100.0
NETMASK0=255.255.255.0
GATEWAY0=192.0.2.10
```
- The ADDRESS0 variable defines the network of the first routing entry.
- The NETMASK0 variable defines the netmask of the first routing entry.
- The GATEWAY0 variable defines the IP address of the gateway to the remote network or host for the first routing entry.
  
  If you add multiple static routes, increase the number in the variable names. Note that the variables for each route must be numbered sequentially. For example, ADDRESS0, ADDRESS1, ADDRESS3, and so on.
Restart the network:
```
# systemctl restart network
```

Verification

Display the IPv4 routes:

ip -4 route

...

198.51.100.0/24

via

192.0.2.10

dev

enp1s0

Troubleshooting

Display the journal entries of the network unit:
```
# journalctl -u network
```
The following are possible error messages and their causes:
- Error: Nexthop has invalid gateway: You specified an IPv4 gateway address in the route- enp1s0
  file that is not in the same subnet as this router.
- RTNETLINK answers: No route to host: You specified an IPv6 gateway address in the route6- enp1s0
  file that is not in the same subnet as this router.
- Error: Invalid prefix for given prefix length: You specified the remote network in the route- enp1s0
  file by using an IP address within the remote network rather than the network address.

Additional resources

/usr/share/doc/network-scripts/sysconfig.txt file

20.11. Creating static routes configuration files in ip-command format when using the legacy network scripts

The legacy network scripts support setting statics routes.

The procedure below configures the following routes:

An IPv4 route to the remote 198.51.100.0/24 network. The corresponding gateway with the IP address 192.0.2.10 is reachable through the enp1s0 interface.
An IPv6 route to the remote 2001:db8:2::/64 network. The corresponding gateway with the IP address 2001:db8:1::10 is reachable through the enp1s0 interface.

Important

IP addresses of the gateways (next hop) must be in the same IP subnet as the host on which you configure the static routes.

The examples in this procedure use configuration entries in ip-command format.

Prerequisites

The gateways for the static route must be directly reachable on the interface.
The NetworkManager package is not installed, or the NetworkManager service is disabled.
The network-scripts package is installed.
The network service is enabled.

Procedure

Add the static IPv4 route to the /etc/sysconfig/network-scripts/route-enp1s0 file:
```
198.51.100.0/24 via 192.0.2.10 dev enp1s0
```
Always specify the network address of the remote network, such as 198.51.100.0. Setting an IP address within the remote network, such as 198.51.100.1 causes that the network scripts fail to add this route.
Add the static IPv6 route to the /etc/sysconfig/network-scripts/route6-enp1s0 file:
```
2001:db8:2::/64 via 2001:db8:1::10 dev enp1s0
```
Restart the network service:
```
# systemctl restart network
```

Verification

Display the IPv4 routes:

ip -4 route

...

198.51.100.0/24

via

192.0.2.10

dev

enp1s0

Display the IPv6 routes:

ip -6 route

...

2001:db8:2::/64

via

2001:db8:1::10

dev

enp1s0

metric

1024

pref

medium

Troubleshooting

Display the journal entries of the network unit:
```
# journalctl -u network
```
The following are possible error messages and their causes:
- Error: Nexthop has invalid gateway: You specified an IPv4 gateway address in the route- enp1s0
  file that is not in the same subnet as this router.
- RTNETLINK answers: No route to host: You specified an IPv6 gateway address in the route6- enp1s0
  file that is not in the same subnet as this router.
- Error: Invalid prefix for given prefix length: You specified the remote network in the route- enp1s0
  file by using an IP address within the remote network rather than the network address.

Additional Resources

/usr/share/doc/network-scripts/sysconfig.txt file

Chapter 21. Configuring policy-based routing to define alternative routes

By default, the kernel in RHEL decides where to forward network packets based on the destination address using a routing table. Policy-based routing enables you to configure complex routing scenarios. For example, you can route packets based on various criteria, such as the source address, packet metadata, or protocol.

Note

On systems that use NetworkManager, only the nmcli utility supports setting routing rules and assigning routes to specific tables.

21.1. Routing traffic from a specific subnet to a different default gateway using NetworkManager

You can use policy-based routing to configure a different default gateway for traffic from certain subnets. For example, you can configure RHEL as a router that, by default, routes all traffic to Internet provider A using the default route. However, traffic received from the internal workstations subnet is routed to provider B.

The procedure assumes the following network topology:

policy based routing

Prerequisites

The system uses NetworkManager to configure the network, which is the default.
The RHEL router you want to set up in the procedure has four network interfaces:
- The enp7s0 interface is connected to the network of provider A. The gateway IP in the provider’s network is 198.51.100.2, and the network uses a /30 network mask.
- The enp1s0 interface is connected to the network of provider B. The gateway IP in the provider’s network is 192.0.2.2, and the network uses a /30 network mask.
- The enp8s0 interface is connected to the 10.0.0.0/24 subnet with internal workstations.
- The enp9s0 interface is connected to the 203.0.113.0/24 subnet with the company’s servers.
Hosts in the internal workstations subnet use 10.0.0.1 as the default gateway. In the procedure, you assign this IP address to the enp8s0 network interface of the router.
Hosts in the server subnet use 203.0.113.1 as the default gateway. In the procedure, you assign this IP address to the enp9s0 network interface of the router.
The firewalld service is enabled and active.

Procedure

Configure the network interface to provider A:
```
# nmcli connection add type ethernet con-name Provider-A ifname enp7s0 ipv4.method manual ipv4.addresses 198.51.100.1/30 ipv4.gateway 198.51.100.2 ipv4.dns 198.51.100.200 connection.zone external
```
The nmcli connection add command creates a NetworkManager connection profile. The command uses the following options:
- type ethernet: Defines that the connection type is Ethernet.
- con-name connection_name
  : Sets the name of the profile. Use a meaningful name to avoid confusion.
- ifname network_device
  : Sets the network interface.
- ipv4.method manual: Enables to configure a static IP address.
- ipv4.addresses IP_address / subnet_mask
  : Sets the IPv4 addresses and subnet mask.
- ipv4.gateway IP_address
  : Sets the default gateway address.
- ipv4.dns IP_of_DNS_server
  : Sets the IPv4 address of the DNS server.
- connection.zone firewalld_zone
  : Assigns the network interface to the defined firewalld zone. Note that firewalld automatically enables masquerading for interfaces assigned to the external zone.
Configure the network interface to provider B:
```
# nmcli connection add type ethernet con-name Provider-B ifname enp1s0 ipv4.method manual ipv4.addresses 192.0.2.1/30 ipv4.routes "0.0.0.0/0 192.0.2.2 table=5000" connection.zone external
```
This command uses the ipv4.routes parameter instead of ipv4.gateway to set the default gateway. This is required to assign the default gateway for this connection to a different routing table (5000) than the default. NetworkManager automatically creates this new routing table when the connection is activated.
Configure the network interface to the internal workstations subnet:
```
# nmcli connection add type ethernet con-name Internal-Workstations ifname enp8s0 ipv4.method manual ipv4.addresses 10.0.0.1/24 ipv4.routes "10.0.0.0/24 table=5000" ipv4.routing-rules "priority 5 from 10.0.0.0/24 table 5000" connection.zone trusted
```
This command uses the ipv4.routes parameter to add a static route to the routing table with ID 5000. This static route for the 10.0.0.0/24 subnet uses the IP of the local network interface to provider B (192.0.2.1) as next hop.

Additionally, the command uses the ipv4.routing-rules parameter to add a routing rule with priority 5 that routes traffic from the 10.0.0.0/24 subnet to table 5000. Low values have a high priority.

Note that the syntax in the ipv4.routing-rules parameter is the same as in an ip rule add command, except that ipv4.routing-rules always requires specifying a priority.

Configure the network interface to the server subnet:

nmcli connection add type ethernet con-name Servers ifname enp9s0 ipv4.method manual ipv4.addresses 203.0.113.1/24 connection.zone trusted

Verification steps

On a RHEL host in the internal workstation subnet:
1. Install the traceroute package:
```
# yum install traceroute
```
2. Use the traceroute utility to display the route to a host on the Internet:
```
# traceroute redhat.com
traceroute to redhat.com (209.132.183.105), 30 hops max, 60 byte packets
 1  10.0.0.1 (10.0.0.1)     0.337 ms  0.260 ms  0.223 ms
 2  192.0.2.1 (192.0.2.1)   0.884 ms  1.066 ms  1.248 ms
 ...
```
  The output of the command displays that the router sends packets over 192.0.2.1, which is the network of provider B.
On a RHEL host in the server subnet:
1. Install the traceroute package:
```
# yum install traceroute
```
2. Use the traceroute utility to display the route to a host on the Internet:
```
# traceroute redhat.com
traceroute to redhat.com (209.132.183.105), 30 hops max, 60 byte packets
 1  203.0.113.1 (203.0.113.1)    2.179 ms  2.073 ms  1.944 ms
 2  198.51.100.2 (198.51.100.2)  1.868 ms  1.798 ms  1.549 ms
 ...
```
  The output of the command displays that the router sends packets over 198.51.100.2, which is the network of provider A.

Troubleshooting steps

On the RHEL router:

Display the rule list:

ip rule list

0: from all lookup local

from 10.0.0.0/24 lookup 5000

32766: from all lookup main 32767: from all lookup default

By default, RHEL contains rules for the tables local, main, and default.

Display the routes in table 5000:

# ip route list table 5000
0.0.0.0/0 via 192.0.2.2 dev enp1s0 proto static metric 100
10.0.0.0/24 dev enp8s0 proto static scope link src 192.0.2.1 metric 102

Display the interfaces and firewall zones:

firewall-cmd --get-active-zones

external interfaces: enp1s0 enp7s0 trusted interfaces: enp8s0 enp9s0

Verify that the external zone has masquerading enabled:

firewall-cmd --info-zone=external

external (active) target: default icmp-block-inversion: no interfaces: enp1s0 enp7s0 sources: services: ssh ports: protocols:

masquerade: yes

...

Additional resources

nm-settings(5) man page
nmcli(1) man page
Is it possible to set up Policy Based Routing with NetworkManager in RHEL?

21.2. Routing traffic from a specific subnet to a different default gateway using RHEL System Roles

To configure policy-based routing remotely and on multiple nodes, you can use the RHEL network System Role. Perform this procedure on the Ansible control node.

This procedure assumes the following network topology:

policy based routing

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on the them.
The hosts or host groups on which you want run this playbook are listed in the Ansible inventory file.

The managed nodes uses the NetworkManager and firewalld services.
The managed nodes you want to configure has four network interfaces:
- The enp7s0 interface is connected to the network of provider A. The gateway IP in the provider’s network is 198.51.100.2, and the network uses a /30 network mask.
- The enp1s0 interface is connected to the network of provider B. The gateway IP in the provider’s network is 192.0.2.2, and the network uses a /30 network mask.
- The enp8s0 interface is connected to the 10.0.0.0/24 subnet with internal workstations.
- The enp9s0 interface is connected to the 203.0.113.0/24 subnet with the company’s servers.
Hosts in the internal workstations subnet use 10.0.0.1 as the default gateway. In the procedure, you assign this IP address to the enp8s0 network interface of the router.
Hosts in the server subnet use 203.0.113.1 as the default gateway. In the procedure, you assign this IP address to the enp9s0 network interface of the router.

Procedure

Create a playbook file, for example ~/pbr.yml, with the following content:

--- - name: Configuring policy-based routing hosts:

managed-node-01.example.com

tasks: - name: Routing traffic from a specific subnet to a different default gateway include_role: name: rhel-system-roles.network vars: network_connections: - name: Provider-A interface_name: enp7s0 type: ethernet autoconnect: True ip: address: - 198.51.100.1/30 gateway4: 198.51.100.2 dns: - 198.51.100.200 state: up zone: external - name: Provider-B interface_name: enp1s0 type: ethernet autoconnect: True ip: address: - 192.0.2.1/30 route: - network: 0.0.0.0 prefix: 0 gateway: 192.0.2.2 table: 5000 state: up zone: external - name: Internal-Workstations interface_name: enp8s0 type: ethernet autoconnect: True ip: address: - 10.0.0.1/24 route: - network: 10.0.0.0 prefix: 24 table: 5000 routing_rule: - priority: 5 from: 10.0.0.0/24 table: 5000 state: up zone: trusted - name: Servers interface_name: enp9s0 type: ethernet autoconnect: True ip: address: - 203.0.113.1/24 state: up zone: trusted

Run the playbook:
```
# ansible-playbook 
~/pbr.yml
```

Verification

On a RHEL host in the internal workstation subnet:
1. Install the traceroute package:
```
# yum install traceroute
```
2. Use the traceroute utility to display the route to a host on the Internet:
```
# traceroute redhat.com
traceroute to redhat.com (209.132.183.105), 30 hops max, 60 byte packets
 1  10.0.0.1 (10.0.0.1)     0.337 ms  0.260 ms  0.223 ms
 2  192.0.2.1 (192.0.2.1)   0.884 ms  1.066 ms  1.248 ms
 ...
```
  The output of the command displays that the router sends packets over 192.0.2.1, which is the network of provider B.
On a RHEL host in the server subnet:
1. Install the traceroute package:
```
# yum install traceroute
```
2. Use the traceroute utility to display the route to a host on the Internet:
```
# traceroute redhat.com
traceroute to redhat.com (209.132.183.105), 30 hops max, 60 byte packets
 1  203.0.113.1 (203.0.113.1)    2.179 ms  2.073 ms  1.944 ms
 2  198.51.100.2 (198.51.100.2)  1.868 ms  1.798 ms  1.549 ms
 ...
```
  The output of the command displays that the router sends packets over 198.51.100.2, which is the network of provider A.

On the RHEL router that you configured using the RHEL System Role:

Display the rule list:

ip rule list

0: from all lookup local

from 10.0.0.0/24 lookup 5000

32766: from all lookup main 32767: from all lookup default

By default, RHEL contains rules for the tables local, main, and default.

Display the routes in table 5000:

# ip route list table 5000
0.0.0.0/0 via 192.0.2.2 dev enp1s0 proto static metric 100
10.0.0.0/24 dev enp8s0 proto static scope link src 192.0.2.1 metric 102

Display the interfaces and firewall zones:

firewall-cmd --get-active-zones

external interfaces: enp1s0 enp7s0 trusted interfaces: enp8s0 enp9s0

Verify that the external zone has masquerading enabled:

firewall-cmd --info-zone=external

external (active) target: default icmp-block-inversion: no interfaces: enp1s0 enp7s0 sources: services: ssh ports: protocols:

masquerade: yes

...

Additional resources

/usr/share/ansible/roles/rhel-system-roles.network/README.md file

21.3. Overview of configuration files involved in policy-based routing when using the legacy network scripts

If you use the legacy network scripts instead of NetworkManager to configure your network, you can also configure policy-based routing.

Note

Configuring the network using the legacy network scripts provided by the network-scripts package is deprecated in RHEL 8. Red Hat recommends that you use NetworkManager to configure policy-based routing. For an example, see Routing traffic from a specific subnet to a different default gateway using NetworkManager.

The following configuration files are involved in policy-based routing when you use the legacy network scripts:

/etc/sysconfig/network-scripts/route-interface: This file defines the IPv4 routes. Use the table option to specify the routing table. For example:
```
192.0.2.0/24 via 198.51.100.1 table 1
203.0.113.0/24 via 198.51.100.2 table 2
```
/etc/sysconfig/network-scripts/route6- interface
: This file defines the IPv6 routes.
/etc/sysconfig/network-scripts/rule-interface: This file defines the rules for IPv4 source networks for which the kernel routes traffic to specific routing tables. For example:
```
from 192.0.2.0/24 lookup 1
from 203.0.113.0/24 lookup 2
```
/etc/sysconfig/network-scripts/rule6- interface
: This file defines the rules for IPv6 source networks for which the kernel routes traffic to specific routing tables.
/etc/iproute2/rt_tables: This file defines the mappings if you want to use names instead of numbers to refer to specific routing tables. For example:
```
1     Provider_A
2     Provider_B
```

Additional resources

ip-route(8) man page
ip-rule(8) man page

21.4. Routing traffic from a specific subnet to a different default gateway using the legacy network scripts

Important

Configuring the network using the legacy network scripts provided by the network-scripts package is deprecated in RHEL 8. Follow the procedure only if you use the legacy network scripts instead of NetworkManager on your host. If you use NetworkManager to manage your network settings, see Routing traffic from a specific subnet to a different default gateway using NetworkManager.

The procedure assumes the following network topology:

policy based routing

Note

The legacy network scripts process configuration files in alphabetical order. Therefore, you must name the configuration files in a way that ensures that an interface, that is used in rules and routes of other interfaces, are up when a depending interface requires it. To accomplish the correct order, this procedure uses numbers in the ifcfg-*, route-*, and rules-* files.

Prerequisites

The NetworkManager package is not installed, or the NetworkManager service is disabled.
The network-scripts package is installed.
The RHEL router you want to set up in the procedure has four network interfaces:
- The enp7s0 interface is connected to the network of provider A. The gateway IP in the provider’s network is 198.51.100.2, and the network uses a /30 network mask.
- The enp1s0 interface is connected to the network of provider B. The gateway IP in the provider’s network is 192.0.2.2, and the network uses a /30 network mask.
- The enp8s0 interface is connected to the 10.0.0.0/24 subnet with internal workstations.
- The enp9s0 interface is connected to the 203.0.113.0/24 subnet with the company’s servers.
Hosts in the internal workstations subnet use 10.0.0.1 as the default gateway. In the procedure, you assign this IP address to the enp8s0 network interface of the router.
Hosts in the server subnet use 203.0.113.1 as the default gateway. In the procedure, you assign this IP address to the enp9s0 network interface of the router.
The firewalld service is enabled and active.

Procedure

Add the configuration for the network interface to provider A by creating the /etc/sysconfig/network-scripts/ifcfg-1_Provider-A file with the following content:
```
TYPE=Ethernet
IPADDR=198.51.100.1
PREFIX=30
GATEWAY=198.51.100.2
DNS1=198.51.100.200
DEFROUTE=yes
NAME=1_Provider-A
DEVICE=enp7s0
ONBOOT=yes
ZONE=external
```
The configuration file uses the following parameters:
- TYPE=Ethernet: Defines that the connection type is Ethernet.
- IPADDR=IP_address
  : Sets the IPv4 address.
- PREFIX=subnet_mask
  : Sets the subnet mask.
- GATEWAY=IP_address
  : Sets the default gateway address.
- DNS1=IP_of_DNS_server
  : Sets the IPv4 address of the DNS server.
- DEFROUTE=yes|no
  : Defines whether the connection is a default route or not.
- NAME=connection_name
  : Sets the name of the connection profile. Use a meaningful name to avoid confusion.
- DEVICE=network_device
  : Sets the network interface.
- ONBOOT=yes: Defines that RHEL starts this connection when the system boots.
- ZONE=firewalld_zone
  : Assigns the network interface to the defined firewalld zone. Note that firewalld automatically enables masquerading for interfaces assigned to the external zone.
Add the configuration for the network interface to provider B:
1. Create the /etc/sysconfig/network-scripts/ifcfg-2_Provider-B file with the following content:
```
TYPE=Ethernet
IPADDR=192.0.2.1
PREFIX=30
DEFROUTE=no
NAME=2_Provider-B
DEVICE=enp1s0
ONBOOT=yes
ZONE=external
```
  Note that the configuration file for this interface does not contain a default gateway setting.
2. Assign the gateway for the 2_Provider-B connection to a separate routing table. Therefore, create the /etc/sysconfig/network-scripts/route-2_Provider-B file with the following content:
```
0.0.0.0/0 via 192.0.2.2 table 5000
```
  This entry assigns the gateway and traffic from all subnets routed through this gateway to table 5000.
Create the configuration for the network interface to the internal workstations subnet:
1. Create the /etc/sysconfig/network-scripts/ifcfg-3_Internal-Workstations file with the following content:
```
TYPE=Ethernet
IPADDR=10.0.0.1
PREFIX=24
DEFROUTE=no
NAME=3_Internal-Workstations
DEVICE=enp8s0
ONBOOT=yes
ZONE=internal
```
2. Add the routing rule configuration for the internal workstation subnet. Therefore, create the /etc/sysconfig/network-scripts/rule-3_Internal-Workstations file with the following content:
```
pri 5 from 10.0.0.0/24 table 5000
```
  This configuration defines a routing rule with priority 5 that routes all traffic from the 10.0.0.0/24 subnet to table 5000. Low values have a high priority.
3. Create the /etc/sysconfig/network-scripts/route-3_Internal-Workstations file with the following content to add a static route to the routing table with ID 5000:
```
10.0.0.0/24 via 192.0.2.1 table 5000
```
  This static route defines that RHEL sends traffic from the 10.0.0.0/24 subnet to the IP of the local network interface to provider B (192.0.2.1). This interface is to routing table 5000 and used as the next hop.
Add the configuration for the network interface to the server subnet by creating the /etc/sysconfig/network-scripts/ifcfg-4_Servers file with the following content:
```
TYPE=Ethernet
IPADDR=203.0.113.1
PREFIX=24
DEFROUTE=no
NAME=4_Servers
DEVICE=enp9s0
ONBOOT=yes
ZONE=internal
```
Restart the network:
```
# systemctl restart network
```

Verification steps

On a RHEL host in the internal workstation subnet:
1. Install the traceroute package:
```
# yum install traceroute
```
2. Use the traceroute utility to display the route to a host on the internet:
```
# traceroute redhat.com
traceroute to redhat.com (209.132.183.105), 30 hops max, 60 byte packets
 1  10.0.0.1 (10.0.0.1)     0.337 ms  0.260 ms  0.223 ms
 2  192.0.2.1 (192.0.2.1)   0.884 ms  1.066 ms  1.248 ms
 ...
```
  The output of the command displays that the router sends packets over 192.0.2.1, which is the network of provider B.
On a RHEL host in the server subnet:
1. Install the traceroute package:
```
# yum install traceroute
```
2. Use the traceroute utility to display the route to a host on the internet:
```
# traceroute redhat.com
traceroute to redhat.com (209.132.183.105), 30 hops max, 60 byte packets
 1  203.0.113.1 (203.0.113.1)    2.179 ms  2.073 ms  1.944 ms
 2  198.51.100.2 (198.51.100.2)  1.868 ms  1.798 ms  1.549 ms
 ...
```
  The output of the command displays that the router sends packets over 198.51.100.2, which is the network of provider A.

Troubleshooting steps

On the RHEL router:

Display the rule list:

ip rule list

0: from all lookup local

from 10.0.0.0/24 lookup 5000

32766: from all lookup main 32767: from all lookup default

By default, RHEL contains rules for the tables local, main, and default.

Display the routes in table 5000:

ip route list table 5000

default via 192.0.2.2 dev enp1s0 10.0.0.0/24 via 192.0.2.1 dev enp1s0

Display the interfaces and firewall zones:

firewall-cmd --get-active-zones

external interfaces: enp1s0 enp7s0 internal interfaces: enp8s0 enp9s0

Verify that the external zone has masquerading enabled:

firewall-cmd --info-zone=external

external (active) target: default icmp-block-inversion: no interfaces: enp1s0 enp7s0 sources: services: ssh ports: protocols:

masquerade: yes

...

Additional resources

Overview of configuration files involved in policy-based routing when using the legacy network scripts
ip-route(8) man page
ip-rule(8) man page
/usr/share/doc/network-scripts/sysconfig.txt file

Chapter 22. Creating a dummy interface

As a Red Hat Enterprise Linux user, you can create and use dummy network interfaces for debugging and testing purposes. A dummy interface provides a device to route packets without actually transmitting them. It enables you to create additional loopback-like devices managed by NetworkManager and makes an inactive SLIP (Serial Line Internet Protocol) address look like a real address for local programs.

22.1. Creating a dummy interface with both an IPv4 and IPv6 address using nmcli

You can create a dummy interface with various settings, such as IPv4 and IPv6 addresses. After creating the dummy interface, NetworkManager automatically assigns it to the default public firewall zone.

Note

To configure a dummy interface without IPv4 or IPv6 address, set the ipv4.method and ipv6.method parameters to disabled. Otherwise, IP auto-configuration fails, and NetworkManager deactivates the connection and removes the dummy device.

Procedure

To create a dummy interface named dummy0 with static IPv4 and IPv6 addresses, enter:

nmcli connection add type dummy ifname

dummy0

ipv4.method manual ipv4.addresses
192.0.2.1/24
ipv6.method manual ipv6.addresses
2001:db8:2::1/64

Optional:To view the dummy interface, enter:

nmcli connection show

NAME UUID TYPE DEVICE enp1s0 db1060e9-c164-476f-b2b5-caec62dc1b05 ethernet ens3 dummy-dummy0 aaf6eb56-73e5-4746-9037-eed42caa8a65 dummy dummy0

Additional resources

nm-settings(5) man page

Chapter 23. Using nmstate-autoconf to automatically configure the network state using LLDP

Network devices can use the Link Layer Discovery Protocol (LLDP) to advertise their identity, capabilities, and neighbors in a LAN. The nmstate-autoconf utility can use this information to automatically configure local network interfaces.

Important

The nmstate-autoconf utility is provided as a Technology Preview only. Technology Preview features are not supported with Red Hat production Service Level Agreements (SLAs), might not be functionally complete, and Red Hat does not recommend using them for production. These previews provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

See Technology Preview Features Support Scope on the Red Hat Customer Portal for information about the support scope for Technology Preview features.

23.1. Using nmstate-autoconf to automatically configure network interfaces

The nmstate-autoconf utility uses LLDP to identify the VLAN settings of interfaces connected to a switch to configure local devices.

This procedure assumes the following scenario and that the switch broadcasts the VLAN settings using LLDP:

The enp1s0 and enp2s0 interfaces of the RHEL server are connected to switch ports that are configured with VLAN ID 100 and VLAN name prod-net.
The enp3s0 interface of the RHEL server is connected to a switch port that is configured with VLAN ID 200 and VLAN name mgmt-net.

The nmstate-autoconf utility then uses this information to create the following interfaces on the server:

bond100 – A bond interface with enp1s0 and enp2s0 as ports.
prod-net – A VLAN interface on top of bond100 with VLAN ID 100.
mgmt-net – A VLAN interface on top of enp3s0 with VLAN ID 200

If you connect multiple network interfaces to different switch ports for which LLDP broadcasts the same VLAN ID, nmstate-autoconf creates a bond with these interfaces and, additionally, configures the common VLAN ID on top of it.

Prerequisites

The nmstate package is installed.
LLDP is enabled on the network switch.
The Ethernet interfaces are up.

Procedure

Enable LLDP on the Ethernet interfaces:

Create a YAML file, for example ~/enable-lldp.yml, with the following contents:

interfaces:
  - name: enp1s0
    type: ethernet
    lldp:
      enabled: true
  - name: enp2s0
    type: ethernet
    lldp:
      enabled: true
  - name: enp3s0
    type: ethernet
    lldp:
      enabled: true

Apply the settings to the system:
```
# nmstatectl apply ~/enable-lldp.yml
```

Configure the network interfaces using LLDP:

Optional, start a dry-run to display and verify the YAML configuration that nmstate-autoconf generates:

nmstate-autoconf -d

enp1s0

,
enp2s0
,
enp3s0

--- interfaces: - name: prod-net type: vlan state: up vlan: base-iface: bond100 id: 100 - name: mgmt-net type: vlan state: up vlan: base-iface: enp3s0 id: 200 - name: bond100 type: bond state: up link-aggregation: mode: balance-rr port: - enp1s0 - enp2s0

Use nmstate-autoconf to generate the configuration based on information received from LLDP, and apply the settings to the system:
```
# nmstate-autoconf 
enp1s0
,enp2s0
,enp3s0
```

Next steps

If there is no DHCP server in your network that provides the IP settings to the interfaces, configure them manual. For details, see:
- Configuring an Ethernet connection
- Configuring network bonding

Verification

Display the settings of the individual interfaces:
```
# nmstatectl show 
<interface_name>
```

Additional resources

nmstate-autoconf(8) man page

Chapter 24. Using LLDP to debug network configuration problems

You can use the Link Layer Discovery Protocol (LLDP) to debug network configuration problems in the topology. This means that, LLDP can report configuration inconsistencies with other hosts or routers and switches.

24.1. Debugging an incorrect VLAN configuration using LLDP information

If you configured a switch port to use a certain VLAN and a host does not receive these VLAN packets, you can use the Link Layer Discovery Protocol (LLDP) to debug the problem. Perform this procedure on the host that does not receive the packets.

Prerequisites

The nmstate package is installed.
The switch supports LLDP.
LLDP is enabled on neighbor devices.

Procedure

Create the ~/enable-LLDP-enp1s0.yml file with the following content:

interfaces: - name:

enp1s0

type: ethernet lldp: enabled: true

Use the ~/enable-LLDP-enp1s0.yml file to enable LLDP on interface enp1s0:
```
# nmstatectl apply ~/enable-LLDP-enp1s0.yml
```

Display the LLDP information:

nmstatectl show enp1s0

- name: enp1s0 type: ethernet state: up ipv4: enabled: false dhcp: false ipv6: enabled: false autoconf: false dhcp: false lldp: enabled: true neighbors: - - type: 5 system-name: Summit300-48 - type: 6 system-description: Summit300-48 - Version 7.4e.1 (Build 5) 05/27/05 04:53:11 - type: 7 system-capabilities: - MAC Bridge component - Router - type: 1 _description: MAC address chassis-id: 00:01:30:F9:AD:A0 chassis-id-type: 4 - type: 2 _description: Interface name port-id: 1/1 port-id-type: 5 - type: 127 ieee-802-1-vlans: - name: v2-0488-03-0505 vid: 488 oui: 00:80:c2 subtype: 3 - type: 127 ieee-802-3-mac-phy-conf: autoneg: true operational-mau-type: 16 pmd-autoneg-cap: 27648 oui: 00:12:0f subtype: 1 - type: 127 ieee-802-1-ppvids: - 0 oui: 00:80:c2 subtype: 2 - type: 8 management-addresses: - address: 00:01:30:F9:AD:A0 address-subtype: MAC interface-number: 1001 interface-number-subtype: 2 - type: 127 ieee-802-3-max-frame-size: 1522 oui: 00:12:0f subtype: 4 mac-address: 82:75:BE:6F:8C:7A mtu: 1500

Verify the output to ensure that the settings match your expected configuration. For example, the LLDP information of the interface connected to the switch shows that the switch port this host is connected to uses VLAN ID 448:
```
- type: 127
        ieee-802-1-vlans:
        - name: v2-0488-03-0505
          vid: 488
```
If the network configuration of the enp1s0 interface uses a different VLAN ID, change it accordingly.

Additional resources

Configuring VLAN tagging

Chapter 25. Manually creating NetworkManager profiles in keyfile format

NetworkManager supports profiles stored in the keyfile format. However, by default, if you use NetworkManager utilities, such as nmcli, the network RHEL System Role, or the nmstate API to manage profiles, NetworkManager still uses profiles in the ifcfg format.

In the next major RHEL release, the keyfile format will be the default.

25.1. The keyfile format of NetworkManager profiles

NetworkManager uses the INI-style keyfile format when it stores connection profiles on disk.

Example of an Ethernet connection profile in keyfile format

[connection]
id=example_connection
uuid=82c6272d-1ff7-4d56-9c7c-0eb27c300029
type=ethernet
autoconnect=true

[ipv4]
method=auto

[ipv6]
method=auto

[ethernet]
mac-address=00:53:00:8f:fa:66

Each section corresponds to a NetworkManager setting name as described in the nm-settings(5) and nm-settings-keyfile(5) man pages. Each key-value-pair in a section is one of the properties listed in the settings specification of the man page.

Most variables in NetworkManager keyfiles have a one-to-one mapping. This means that a NetworkManager property is stored in the keyfile as a variable of the same name and in the same format. However, there are exceptions, mainly to make the keyfile syntax easier to read. For a list of these exceptions, see the nm-settings-keyfile(5) man page.

Important

For security reasons, because connection profiles can contain sensitive information, such as private keys and passphrases, NetworkManager uses only configuration files owned by the root and that are only readable and writable by root.

Depending on the purpose of the connection profile, save it in one of the following directories:

/etc/NetworkManager/system-connections/: The general location for persistent profiles created by the user that can also be edited. NetworkManager copies them automatically to /etc/NetworkManager/system-connections/.
/run/NetworkManager/system-connections/: For temporary profiles that are automatically removed when you reboot the system.
/usr/lib/NetworkManager/system-connections/: For pre-deployed immutable profiles. When you edit such a profile using the NetworkManager API, NetworkManager copies this profile to either the persistent or temporary storage.

NetworkManager does not automatically reload profiles from disk. When you create or update a connection profile in keyfile format, use the nmcli connection reload command to inform NetworkManager about the changes.

25.2. Creating a NetworkManager profile in keyfile format

You can manually create a NetworkManager connection profile in keyfile format.

Note

Manually creating or updating the configuration files can result in an unexpected or non-functional network configuration. Red Hat recommends that you use NetworkManager utilities, such as nmcli, the network RHEL System Role, or the nmstate API to manage NetworkManager connections.

Procedure

If you create a profile for a hardware interface, such as Ethernet, display the MAC address of this interface:

ip address show

enp1s0

2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether

00:53:00:8f:fa:66

brd ff:ff:ff:ff:ff:ff

Create a connection profile. For example, for a connection profile of an Ethernet device that uses DHCP, create the /etc/NetworkManager/system-connections/example.nmconnection file with the following content:
```
[connection]
id=example_connection
type=ethernet
autoconnect=true

[ipv4]
method=auto

[ipv6]
method=auto

[ethernet]
mac-address=00:53:00:8f:fa:66
```
Note

You can use any file name with a .nmconnection suffix. However, when you later use nmcli commands to manage the connection, you must use the connection name set in the id variable when you refer to this connection. When you omit the id variable, use the file name without the .nmconnection to refer to this connection.

Set permissions on the configuration file so that only the root user can read and update it:

chown root:root

/etc/NetworkManager/system-connections/example.nmconnection

chmod 600

/etc/NetworkManager/system-connections/example.nmconnection

Reload the connection profiles:
```
# nmcli connection reload
```

Verify that NetworkManager read the profile from the configuration file:

nmcli -f NAME,UUID,FILENAME connection

NAME UUID FILENAME

example-connection

86da2486-068d-4d05-9ac7-957ec118afba

/etc/NetworkManager/system-connections/example.nmconnection

...

If the command does not show the newly added connection, verify that the file permissions and the syntax you used in the file are correct.

Optional: If you set the autoconnect variable in the profile to false, activate the connection:
```
# nmcli connection up example_connection
```

Verification

Display the connection profile:

nmcli connection show

example_connection

Display the IP settings of the interface:
```
# ip address show enp1s0
```

Additional resources

nm-settings-keyfile (5)

25.3. Migrating NetworkManager profiles from ifcfg to keyfile format

You can use the nmcli connection migrate command to migrate your existing ifcfg connection profiles to the keyfile format. This way, all your connection profiles will be in one location and in the preferred format.

Prerequisites

You have connection profiles in ifcfg format in the /etc/sysconfig/network-scripts/ directory.

Procedure

Migrate the connection profiles:

nmcli connection migrate

Connection 'enp1s0' (43ed18ab-f0c4-4934-af3d-2b3333948e45) successfully migrated. Connection 'enp2s0' (883333e8-1b87-4947-8ceb-1f8812a80a9b) successfully migrated. ...

Verification

Optionally, you can verify that you successfully migrated all your connection profiles:

nmcli

-f TYPE,FILENAME,NAME

connection

TYPE FILENAME NAME ethernet /etc/NetworkManager/system-connections/enp1s0.nmconnection enp1s0 ethernet /etc/NetworkManager/system-connections/enp2s0.nmconnection enp2s0 ...

Additional resources

nm-settings-keyfile(5)
nm-settings-ifcfg-rh(5)
nmcli(1)

25.4. Using nmcli to create keyfile connection profiles in offline mode

Red Hat recommends using NetworkManager utilities, such as nmcli, the network RHEL System Role, or the nmstate API to manage NetworkManager connections, to create and update configuration files. However, you can also create various connection profiles in the keyfile format in offline mode using the nmcli --offline connection add command.

The offline mode ensures that nmcli operates without the NetworkManager service to produce keyfile connection profiles through standard output. This feature can be useful if:

You want to create your connection profiles that need to be pre-deployed somewhere. For example in a container image, or as an RPM package.
You want to create your connection profiles in an environment where the NetworkManager service is not available. For example when you want to use the chroot utility. Alternatively, when you want to create or modify the network configuration of the RHEL system to be installed through the Kickstart %post script.

You can create the following connection profile types:

static Ethernet connection
dynamic Ethernet connection
network bond
network bridge
VLAN or any kind of supported connections

Warning

Manually creating or updating the configuration files can result in an unexpected or non-functional network configuration.

Prerequisites

The NetworkManager service is stopped.

Procedure

Create a new connection profile in the keyfile format. For example, for a connection profile of an Ethernet device that does not use DHCP, run a similar nmcli command:
```
# nmcli --offline connection add type ethernet con-name 
Example-Connection
 ipv4.addresses 192.0.2.1/24
 ipv4.dns 192.0.2.200
 ipv4.method manual > /etc/NetworkManager/system-connections/output.nmconnection
```
Note

The connection name you specified with the con-name key is saved into the id variable of the generated profile. When you use the nmcli command to manage this connection later, specify the connection as follows:
- When the id variable is not omitted, use the connection name, for example Example-Connection.
- When the id variable is omitted, use the file name without the .nmconnection suffix, for example output.

Set permissions to the configuration file so that only the root user can read and update it:

chmod 600 /etc/NetworkManager/system-connections/

output.nmconnection

chown root:root /etc/NetworkManager/system-connections/

output.nmconnection

Start the NetworkManager service:

systemctl start NetworkManager.service

Optional: If you set the autoconnect variable in the profile to false, activate the connection:
```
# nmcli connection up 
Example-Connection
```

Verification

Verify that the NetworkManager service is running:

# systemctl status NetworkManager.service
● NetworkManager.service - Network Manager
   Loaded: loaded (/usr/lib/systemd/system/NetworkManager.service; enabled; vendor preset: enabled)
   Active: active (running) since Wed 2022-08-03 13:08:32 CEST; 1min 40s ago
     Docs: man:NetworkManager(8)
 Main PID: 7138 (NetworkManager)
    Tasks: 3 (limit: 22901)
   Memory: 4.4M
   CGroup: /system.slice/NetworkManager.service
           └─7138 /usr/sbin/NetworkManager --no-daemon

Aug 03 13:08:33 example.com NetworkManager[7138]: <info>  [1659524913.3600] device (vlan20): state change: secondaries -> activated (reason 'none', sys-iface-state: 'assume')
Aug 03 13:08:33 example.com NetworkManager[7138]: <info>  [1659524913.3607] device (vlan20): Activation: successful, device activated.
...

Verify that NetworkManager can read the profile from the configuration file:

nmcli -f TYPE,FILENAME,NAME connection

TYPE FILENAME NAME

ethernet /etc/NetworkManager/system-connections/output.nmconnection Example-Connection

ethernet /etc/sysconfig/network-scripts/ifcfg-enp1s0 enp1s0 ...

If the output does not show the newly created connection, verify that the keyfile permissions and the syntax you used are correct.

Display the connection profile:

nmcli connection show

Example-Connection

connection.id: Example-Connection connection.uuid: 232290ce-5225-422a-9228-cb83b22056b4 connection.stable-id: -- connection.type: 802-3-ethernet connection.interface-name: -- connection.autoconnect: yes ...

Additional resources

nmcli(1)
nm-settings-keyfile(5)
The keyfile format of NetworkManager profiles
Configuring a static Ethernet connection using nmcli
Configuring a dynamic Ethernet connection using nmcli
Configuring VLAN tagging using nmcli commands
Configuring a network bridge using nmcli commands
Configuring a network bond using nmcli commands

Chapter 26. Systemd network targets and services

NetworkManager configures the network during the system boot process. However, when booting with a remote root (/), such as if the root directory is stored on an iSCSI device, the network settings are applied in the initial RAM disk (initrd) before RHEL is started. For example, if the network configuration is specified on the kernel command line using rd.neednet=1 or a configuration is specified to mount remote file systems, then the network settings are applied on initrd.

RHEL uses the network and network-online targets and the NetworkManager-wait-online service while applying network settings. Also, you can configure systemd services to start after the network is fully available if these services cannot dynamically reload.

26.1. Differences between the network and network-online systemd target

Systemd maintains the network and network-online target units. The special units such as NetworkManager-wait-online.service, have WantedBy=network-online.target and Before=network-online.target parameters. If enabled, these units get started with network-online.target and delay the target to be reached until some form of network connectivity is established. They delay the network-online target until the network is connected.

The network-online target starts a service, which adds substantial delays to further execution. Systemd automatically adds dependencies with Wants and After parameters for this target unit to all the System V (SysV) init script service units with a Linux Standard Base (LSB) header referring to the $network facility. The LSB header is metadata for init scripts. You can use it to specify dependencies. This is similar to the systemd target.

The network target does not significantly delay the execution of the boot process. Reaching the network target means that the service that is responsible for setting up the network has started. However, it does not mean that a network device was configured. This target is important during the shutdown of the system. For example, if you have a service that was ordered after the network target during bootup, then this dependency is reversed during the shutdown. The network does not get disconnected until your service has been stopped. All mount units for remote network file systems automatically start the network-online target unit and order themselves after it.

Note

The network-online target unit is only useful during the system starts. After the system has completed booting up, this target does not track the online state of the network. Therefore, you cannot use network-online to monitor the network connection. This target provides a one-time system startup concept.

26.2. Overview of NetworkManager-wait-online

The synchronous legacy network scripts iterate through all configuration files to set up devices. They apply all network-related configurations and ensure that the network is online.

The NetworkManager-wait-online service waits with a timeout for the network to be configured. This network configuration involves plugging-in an Ethernet device, scanning for a Wi-Fi device, and so forth. NetworkManager automatically activates suitable profiles that are configured to start automatically. The failure of the automatic activation process due to a DHCP timeout or similar event might keep NetworkManager busy for an extended period of time. Depending on the configuration, NetworkManager retries activating the same profile or a different profile.

When the startup completes, either all profiles are in a disconnected state or are successfully activated. You can configure profiles to auto-connect. The following are a few examples of parameters that set timeouts or define when the connection is considered active:

connection.wait-device-timeout – sets the timeout for the driver to detect the device
ipv4.may-fail and ipv6.may-fail – sets activation with one IP address family ready, or whether a particular address family must have completed configuration.
ipv4.gateway-ping-timeout – delays activation.

Additional resources

nm-settings(5) man page

26.3. Configuring a systemd service to start after the network has been started

Red Hat Enterprise Linux installs systemd service files in the /usr/lib/systemd/system/ directory. This procedure creates a drop-in snippet for a service file in /etc/systemd/system/service_name.service.d/ that is used together with the service file in /usr/lib/systemd/system/ to start a particular service after the network is online. It has a higher priority if settings in the drop-in snippet overlap with the ones in the service file in /usr/lib/systemd/system/.

Procedure

To open the service file in the editor, enter:

# systemctl edit service_name
Enter the following, and save the changes:
```
[Unit]
After=network-online.target
```
Reload the systemd service.

# systemctl daemon-reload

Chapter 27. Linux traffic control

Linux offers tools for managing and manipulating the transmission of packets. The Linux Traffic Control (TC) subsystem helps in policing, classifying, shaping, and scheduling network traffic. TC also mangles the packet content during classification by using filters and actions. The TC subsystem achieves this by using queuing disciplines (qdisc), a fundamental element of the TC architecture.

The scheduling mechanism arranges or rearranges the packets before they enter or exit different queues. The most common scheduler is the First-In-First-Out (FIFO) scheduler. You can do the qdiscs operations temporarily using the tc utility or permanently using NetworkManager.

In Red Hat Enterprise Linux, you can configure default queueing disciplines in various ways to manage the traffic on a network interface.

27.1. Overview of queuing disciplines

Queuing disciplines (qdiscs) help with queuing up and, later, scheduling of traffic transmission by a network interface. A qdisc has two operations;

enqueue requests so that a packet can be queued up for later transmission and
dequeue requests so that one of the queued-up packets can be chosen for immediate transmission.

Every qdisc has a 16-bit hexadecimal identification number called a handle, with an attached colon, such as 1: or abcd:. This number is called the qdisc major number. If a qdisc has classes, then the identifiers are formed as a pair of two numbers with the major number before the minor, <major>:<minor>, for example abcd:1. The numbering scheme for the minor numbers depends on the qdisc type. Sometimes the numbering is systematic, where the first-class has the ID <major>:1, the second one <major>:2, and so on. Some qdiscs allow the user to set class minor numbers arbitrarily when creating the class.

Classful qdiscs

Different types of qdiscs exist and help in the transfer of packets to and from a networking interface. You can configure qdiscs with root, parent, or child classes. The point where children can be attached are called classes. Classes in qdisc are flexible and can always contain either multiple children classes or a single child, qdisc. There is no prohibition against a class containing a classful qdisc itself, this facilitates complex traffic control scenarios.

Classful qdiscs do not store any packets themselves. Instead, they enqueue and dequeue requests down to one of their children according to criteria specific to the qdisc. Eventually, this recursive packet passing ends up where the packets are stored (or picked up from in the case of dequeuing).

Classless qdiscs

Some qdiscs contain no child classes and they are called classless qdiscs. Classless qdiscs require less customization compared to classful qdiscs. It is usually enough to attach them to an interface.

Additional resources

tc(8) man page
tc-actions(8) man page

27.2. Inspecting qdiscs of a network interface using the tc utility

By default, Red Hat Enterprise Linux systems use fq_codel qdisc. You can inspect the qdisc counters using the tc utility.

Procedure

Optional: View your current qdisc:

# tc qdisc show dev enp0s1

Inspect the current qdisc counters:

tc -s qdisc show dev

enp0s1

qdisc fq_codel 0: root refcnt 2 limit 10240p flows 1024 quantum 1514 target 5.0ms interval 100.0ms memory_limit 32Mb ecn Sent 1008193 bytes 5559 pkt (dropped 233, overlimits 55 requeues 77) backlog 0b 0p requeues 0

dropped – the number of times a packet is dropped because all queues are full
overlimits – the number of times the configured link capacity is filled
sent – the number of dequeues

27.3. Updating the default qdisc

If you observe networking packet losses with the current qdisc, you can change the qdisc based on your network-requirements.

Procedure

View the current default qdisc:

# sysctl -a | grep qdisc
net.core.default_qdisc = fq_codel

View the qdisc of current Ethernet connection:

tc -s qdisc show dev

enp0s1

qdisc fq_codel 0: root refcnt 2 limit 10240p flows 1024 quantum 1514 target 5.0ms interval 100.0ms memory_limit 32Mb ecn Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0) backlog 0b 0p requeues 0 maxpacket 0 drop_overlimit 0 new_flow_count 0 ecn_mark 0 new_flows_len 0 old_flows_len 0

Update the existing qdisc:

# sysctl -w net.core.default_qdisc=pfifo_fast
To apply the changes, reload the network driver:

# rmmod NETWORKDRIVERNAME

# modprobe NETWORKDRIVERNAME
Start the network interface:

# ip link set enp0s1 up

Verification steps

View the qdisc of the Ethernet connection:

tc -s qdisc show dev

enp0s1

qdisc

pfifo_fast

0: root refcnt 2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1 Sent 373186 bytes 5333 pkt (dropped 0, overlimits 0 requeues 0) backlog 0b 0p requeues 0 ....

Additional resources

How to set sysctl variables on Red Hat Enterprise Linux

27.4. Temporarily setting the current qdisk of a network interface using the tc utility

You can update the current qdisc without changing the default one.

Procedure

Optional: View the current qdisc:

# tc -s qdisc show dev enp0s1
Update the current qdisc:

# tc qdisc replace dev enp0s1 root htb

Verification steps

View the updated current qdisc:

tc -s qdisc show dev

enp0s1

qdisc htb 8001: root refcnt 2 r2q 10 default 0 direct_packets_stat 0 direct_qlen 1000 Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0) backlog 0b 0p requeues 0

27.5. Permanently setting the current qdisk of a network interface using NetworkManager

You can update the current qdisc value of a NetworkManager connection.

Procedure

Optional: View the current qdisc:

tc qdisc show dev

enp0s1

qdisc fq_codel 0: root refcnt 2

Update the current qdisc:

nmcli connection modify

enp0s1

tc.qdiscs ‘root pfifo_fast’

Optional: To add another qdisc over the existing qdisc, use the +tc.qdisc option:
```
# nmcli connection modify 
enp0s1
 +tc.qdisc ‘ingress handle ffff:’
```
Activate the changes:
```
# nmcli connection up 
enp0s1
```

Verification steps

View current qdisc the network interface:

tc qdisc show dev

enp0s1

qdisc

pfifo_fast

8001: root refcnt 2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1 qdisc ingress ffff: parent ffff:fff1 ----------------

Additional resources

nm-settings(5) man page

27.6. Available qdiscs in RHEL

Each qdisc addresses unique networking-related issues. The following is the list of qdiscs available in RHEL. You can use any of the following qdisc to shape network traffic based on your networking requirements.

Table 27.1. Available schedulers in RHEL

qdisc nameIncluded inOffload support

Asynchronous Transfer Mode (ATM)

kernel-modules-extra

Class-Based Queueing

kernel-modules-extra

Credit-Based Shaper

kernel-modules-extra

Yes

CHOose and Keep for responsive flows, CHOose and Kill for unresponsive flows (CHOKE)

kernel-modules-extra

Controlled Delay (CoDel)

kernel-core

Deficit Round Robin (DRR)

kernel-modules-extra

Differentiated Services marker (DSMARK)

kernel-modules-extra

Enhanced Transmission Selection (ETS)

kernel-modules-extra

Yes

Fair Queue (FQ)

kernel-core

Fair Queuing Controlled Delay (FQ_CODel)

kernel-core

Generalized Random Early Detection (GRED)

kernel-modules-extra

Hierarchical Fair Service Curve (HSFC)

kernel-core

Heavy-Hitter Filter (HHF)

kernel-core

Hierarchy Token Bucket (HTB)

kernel-core

INGRESS

kernel-core

Yes

Multi Queue Priority (MQPRIO)

kernel-modules-extra

Yes

Multiqueue (MULTIQ)

kernel-modules-extra

Yes

Network Emulator (NETEM)

kernel-modules-extra

Proportional Integral-controller Enhanced (PIE)

kernel-core

PLUG

kernel-core

Quick Fair Queueing (QFQ)

kernel-modules-extra

Random Early Detection (RED)

kernel-modules-extra

Yes

Stochastic Fair Blue (SFB)

kernel-modules-extra

Stochastic Fairness Queueing (SFQ)

kernel-core

Token Bucket Filter (TBF)

kernel-core

Yes

Trivial Link Equalizer (TEQL)

kernel-modules-extra

Important

The qdisc offload requires hardware and driver support on NIC.

Additional resources

tc(8) man page

Chapter 28. Getting started with Multipath TCP

Transmission Control Protocol (TCP) ensures reliable delivery of the data through the Internet and automatically adjusts its bandwidth in response to network load. Multipath TCP (MPTCP) is an extension to the original TCP protocol (single-path). MPTCP enables a transport connection to operate across multiple paths simultaneously, and brings network connection redundancy to user endpoint devices.

28.1. Understanding MPTCP

The Multipath TCP (MPTCP) protocol allows for simultaneous usage of multiple paths between connection endpoints. The protocol design improves connection stability and also brings other benefits compared to the single-path TCP.

Note

In MPTCP terminology, links are considered as paths.

The following are some of the advantages of using MPTCP:

It allows a connection to simultaneously use multiple network interfaces.
In case a connection is bound to a link speed, the usage of multiple links can increase the connection throughput. Note, that in case of the connection is bound to a CPU, the usage of multiple links causes the connection slowdown.
It increases the resilience to link failures.

For more details about MPTCP, we highly recommend you review the Additional resources.

Additional resources

Understanding Multipath TCP: High availability for endpoints and the networking highway of the future
RFC8684: TCP Extensions for Multipath Operation with Multiple Addresses
Multipath TCP on Red Hat Enterprise Linux 8.3: From 0 to 1 subflows

28.2. Preparing RHEL to enable MPTCP support

By default the MPTCP support is disabled in RHEL. Enable MPTCP so that applications that support this feature can use it. Additionally, you have to configure user space applications to force use MPTCP sockets if those applications have TCP sockets by default.

You can use the sysctl utility to enable MPTCP support and prepare RHEL for enabling MPTCP for applications system-wide using a SystemTap script.

Prerequisites

The following packages are installed:

systemtap
iperf3

Procedure

Enable MPTCP sockets in the kernel:

echo "net.mptcp.enabled=1" > /etc/sysctl.d/90-enable-MPTCP.conf

sysctl -p /etc/sysctl.d/90-enable-MPTCP.conf

Verify that MPTCP is enabled in the kernel:

# sysctl -a | grep mptcp.enabled
net.mptcp.enabled = 1

Create a mptcp-app.stap file with the following content:

#!/usr/bin/env stap

%{
#include <linux/in.h>
#include <linux/ip.h>
%}

/* RSI contains 'type' and RDX contains 'protocol'.
 */

function mptcpify () %{
    if (CONTEXT->kregs->si == SOCK_STREAM &&
        (CONTEXT->kregs->dx == IPPROTO_TCP ||
         CONTEXT->kregs->dx == 0)) {
                CONTEXT->kregs->dx = IPPROTO_MPTCP;
                STAP_RETVALUE = 1;
    } else {
           STAP_RETVALUE = 0;
    }
%}

probe kernel.function("__sys_socket") {
        if (mptcpify() == 1) {
                printf("command %16s mptcpified\n", execname());
        }
}

Force user space applications to create MPTCP sockets instead of TCP ones:
```
# stap -vg mptcp-app.stap
```
Note: This operation affects all TCP sockets which are started after the command. The applications will continue using TCP sockets after you interrupt the command above with Ctrl+C.

Alternatively, to allow MPTCP usage to only specific application, you can modify the mptcp-app.stap file with the following content:

#!/usr/bin/env stap

%{
#include <linux/in.h>
#include <linux/ip.h>
%}

/* according to [1], RSI contains 'type' and RDX
 * contains 'protocol'.
 * [1] https://github.com/torvalds/linux/blob/master/arch/x86/entry/entry_64.S#L79
 */

function mptcpify () %{
	if (CONTEXT->kregs->si == SOCK_STREAM &&
	    (CONTEXT->kregs->dx == IPPROTO_TCP ||
	     CONTEXT->kregs->dx == 0)) {
		CONTEXT->kregs->dx = IPPROTO_MPTCP;
		STAP_RETVALUE = 1;
	} else {
		STAP_RETVALUE = 0;
	}
%}

probe kernel.function("__sys_socket") {
	cur_proc = execname()
	if ((cur_proc == @1) && (mptcpify() == 1)) {
		printf("command %16s mptcpified\n", cur_proc);
	}
}

In case of alternative choice, assuming, you want to force the iperf3 tool to use MPTCP instead of TCP. To do so, enter the following command:
```
# stap -vg mptcp-app.stap iperf3
```

After the mptcp-app.stap script installs the kernel probe, the following warnings appear in the kernel dmesg output

dmesg

... [ 1752.694072] Kprobes globally unoptimized [ 1752.730147] stap_1ade3b3356f3e68765322e26dec00c3d_1476: module_layout: kernel tainted. [ 1752.732162] Disabling lock debugging due to kernel taint [ 1752.733468] stap_1ade3b3356f3e68765322e26dec00c3d_1476: loading out-of-tree module taints kernel. [ 1752.737219] stap_1ade3b3356f3e68765322e26dec00c3d_1476: module verification failed: signature and/or required key missing - tainting kernel [ 1752.737219] stap_1ade3b3356f3e68765322e26dec00c3d_1476 (mptcp-app.stap): systemtap: 4.5/0.185, base: ffffffffc0550000, memory: 224data/32text/57ctx/65638net/367alloc kb, probes: 1

Start the iperf3 server:
```
# iperf3 -s

Server listening on 5201
```
Connect the client to the server:
```
# iperf3 -c 127.0.0.1 -t 3
```

After the connection is established, verify the ss output to see the subflow-specific status:

ss -nti '( dport :5201 )'

State Recv-Q Send-Q Local Address:Port Peer Address:Port Process ESTAB 0 0 127.0.0.1:41842 127.0.0.1:5201 cubic wscale:7,7 rto:205 rtt:4.455/8.878 ato:40 mss:21888 pmtu:65535 rcvmss:536 advmss:65483 cwnd:10 bytes_sent:141 bytes_acked:142 bytes_received:4 segs_out:8 segs_in:7 data_segs_out:3 data_segs_in:3 send 393050505bps lastsnd:2813 lastrcv:2772 lastack:2772 pacing_rate 785946640bps delivery_rate 10944000000bps delivered:4 busy:41ms rcv_space:43690 rcv_ssthresh:43690 minrtt:0.008 tcp-ulp-mptcp flags:Mmec token:0000(id:0)/2ff053ec(id:0) seq:3e2cbea12d7673d4 sfseq:3 ssnoff:ad3d00f4 maplen:2

Verify MPTCP counters by using nstat MPTcp* command:

# nstat MPTcp*

#kernel
MPTcpExtMPCapableSYNRX          2                  0.0
MPTcpExtMPCapableSYNTX          2                  0.0
MPTcpExtMPCapableSYNACKRX       2                  0.0
MPTcpExtMPCapableACKRX          2                  0.0

Additional resources

How can I download or install debuginfo packages for RHEL systems?
tcp(7) man page
mptcpize(8) man page

28.3. Using iproute2 to temporarily configure and enable multiple paths for MPTCP applications

Each MPTCP connection uses a single subflow similar to plain TCP. To leverage the MPTCP benefits, specify a higher limit for maximum number of subflows for each MPTCP connection. Then configure additional endpoints to create those subflows.

Important

The configuration in this procedure will not persist after rebooting your machine.

Note that MPTCP does not yet support mixed IPv6 and IPv4 endpoints for the same socket. Use endpoints belonging to the same address family.

Prerequisites

The iperf3 package is installed
Server network interface settings:
- enp4s0:
  
  192.0.2.1/24
- enp1s0:
  
  198.51.100.1/24
Client network interface settings:
- enp4s0f0:
  
  192.0.2.2/24
- enp4s0f1:
  
  198.51.100.2/24

Procedure

Set the per connection additional subflow limits to 1 on the server:
```
# ip mptcp limits set subflow 
1
```
Note, that sets a maximum number of additional subflows which each connection can have, excluding the initial one.
Set the per connection and additional subflow limits to 1 on the client:
```
# ip mptcp limits set subflow 
1
 add_addr_accepted 1
```
Add IP address 198.51.100.1 as a new MPTCP endpoint on the server:
```
# ip mptcp endpoint add 
198.51.100.1
 dev enp1s0
 signal
```
The signal option ensures that the ADD_ADDR packet is sent after the three-way-handshake.
Start the iperf3 server:
```
# iperf3 -s

Server listening on 5201
```
Connect the client to the server:
```
# iperf3 -c 192.0.2.1 -t 3
```

Verification steps

Verify the connection is established:
```
# ss -nti '( sport :5201 )'
```
Verify the connection and IP address limit:
```
# ip mptcp limit show
```
Verify the newly added endpoint:
```
# ip mptcp endpoint show
```

Verify MPTCP counters by using the nstat MPTcp* command on a server:

nstat MPTcp

* #kernel MPTcpExtMPCapableSYNRX 2 0.0 MPTcpExtMPCapableACKRX 2 0.0 MPTcpExtMPJoinSynRx 2 0.0 MPTcpExtMPJoinAckRx 2 0.0 MPTcpExtEchoAdd 2 0.0

Additional resources

ip-mptcp(8) man page
mptcpize(8) man page

28.4. Permanently configuring multiple paths for MPTCP applications

You can configure MultiPath TCP (MPTCP) using the nmcli command to permanently establish multiple subflows between a source and destination system. The subflows can use different resources, different routes to the destination, and even different networks. Such as Ethernet, cellular, wifi, and so on. As a result, you achieve combined connections, which increase network resilience and throughput.

The server uses the following network interfaces in our example:

enp4s0:

192.0.2.1/24
enp1s0:

198.51.100.1/24
enp7s0:

192.0.2.3/24

The client uses the following network interfaces in our example:

enp4s0f0:

192.0.2.2/24
enp4s0f1:

198.51.101.2/24
enp6s0:

192.0.2.5/24

Prerequisites

You configured the default gateway on the relevant interfaces.

Procedure

Enable MPTCP sockets in the kernel:

echo "net.mptcp.enabled=1" > /etc/sysctl.d/90-enable-MPTCP.conf

sysctl -p /etc/sysctl.d/90-enable-MPTCP.conf

Set the per connection additional subflow limits to 2 on the server:
1. Create the /etc/systemd/system/set_mptcp_limit.service file with the following content:
```
[Unit]
Description=Set MPTCP subflow limit to 2
After=network.target

[Service]
ExecStart=ip mptcp limits set subflows 2
Type=oneshot

[Install]
WantedBy=multi-user.target
```
  In RHEL 8, it is not possible to set the subflow limits using the nmcli utility. Nor is the subflow limit defined in the RHEL kernel configuration. Instead, use a similar oneshot unit that executes the ip mptcp limits set subflows 2 command after your network (network.target) is operational during every boot process.
  
  The ip mptcp limits set subflows 2 command sets the maximum number of additional subflows for each connection, so 3 in total.
2. Enable the set_mptcp_limit service:
```
# systemctl enable --now set_mptcp_limit
```
Enable MPTCP on all connection profiles that you want to use for connection aggregation:
```
# nmcli connection modify 
<profile_name>
 connection.mptcp-flags signal,subflow,also-without-default-route
```
The connection.mptcp-flags parameter configures MPTCP endpoints and the IP address flags. If MPTCP is enabled in a NetworkManager connection profile, the setting will configure the IP addresses of the relevant network interface as MPTCP endpoints.

By default, NetworkManager does not add MPTCP flags to IP addresses if there is no default gateway. If you want to bypass that check, you need to use also the also-without-default-route flag.

Verification

Verify that you enabled the MPTCP kernel parameter:
```
# sysctl net.mptcp.enabled
net.mptcp.enabled = 1
```

Verify that you set the subflow limit correctly:

ip mptcp limit show

add_addr_accepted 1 subflows 2

Verify that you configured the per-address MPTCP setting correctly:

ip mptcp endpoint show

192.0.2.1 id 1 subflow dev enp4s0 198.51.100.1 id 2 subflow dev enp1s0 192.0.2.3 id 3 subflow dev enp7s0 ...

Additional resources

nm-settings-nmcli(5)
ip-mptcp(8)
Section 28.1, “Understanding MPTCP”
Understanding Multipath TCP: High availability for endpoints and the networking highway of the future
RFC8684: TCP Extensions for Multipath Operation with Multiple Addresses
Using Multipath TCP to better survive outages and increase bandwidth

28.5. Monitoring MPTCP sub-flows

The life cycle of a multipath TCP (MPTCP) socket can be complex: The main MPTCP socket is created, the MPTCP path is validated, one or more sub-flows are created and eventually removed. Finally, the MPTCP socket is terminated.

The MPTCP protocol allows monitoring MPTCP-specific events related to socket and sub-flow creation and deletion, using the ip utility provided by the iproute package. This utility uses the netlink interface to monitor MPTCP events.

This procedure demonstrates how to monitor MPTCP events. For that, it simulates a MPTCP server application, and a client connects to this service. The involved clients in this example use the following interfaces and IP addresses:

Server: 192.0.2.1
Client (Ethernet connection): 192.0.2.2
Client (WiFi connection): 192.0.2.3

To simplify this example, all interfaces are within the same subnet. This is not a requirement. However, it is important that routing has been configured correctly, and the client can reach the server via both interfaces.

Prerequisites

A RHEL client with two network interfaces, such as a laptop with Ethernet and WiFi
The client can connect to the server via both interfaces
A RHEL server
Both the client and the server run RHEL 8.6 or later

Procedure

Set the per connection additional subflow limits to 1 on both client and server:
```
# ip mptcp limits set add_addr_accepted 0 subflows 1
```
On the server, to simulate a MPTCP server application, start netcat (nc) in listen mode with enforced MPTCP sockets instead of TCP sockets:
```
# nc -l -k -p 
12345
```
The -k option causes that nc does not close the listener after the first accepted connection. This is required to demonstrate the monitoring of sub-flows.
On the client:
1. Identify the interface with the lowest metric:
```
# ip -4 route
192.0.2.0/24 dev enp1s0 proto kernel scope link src 192.0.2.2 metric 100
192.0.2.0/24 dev wlp1s0 proto kernel scope link src 192.0.2.3 metric 600
```
  The enp1s0 interface has a lower metric than wlp1s0. Therefore, RHEL uses enp1s0 by default.
2. On the first terminal, start the monitoring:
```
# ip mptcp monitor
```
3. On the second terminal, start a MPTCP connection to the server:
```
# nc 192.0.2.1 12345
```
  RHEL uses the enp1s0 interface and its associated IP address as a source for this connection.
  
  On the monitoring terminal, the `ip mptcp monitor ` command now logs:
```
[       CREATED] token=63c070d2 remid=0 locid=0 saddr4=192.0.2.2 daddr4=192.0.2.1 sport=36444 dport=12345
```
  The token identifies the MPTCP socket as an unique ID, and later it enables you to correlate MPTCP events on the same socket.
4. On the terminal with the running nc connection to the server, press Enter. This first data packet fully establishes the connection. Note that, as long as no data has been sent, the connection is not established.
  
  On the monitoring terminal, ip mptcp monitor now logs:
```
[   ESTABLISHED] token=63c070d2 remid=0 locid=0 saddr4=192.0.2.2 daddr4=192.0.2.1 sport=36444 dport=12345
```
5. Optional: Display the connections to port 12345 on the server:
```
# ss -taunp | grep ":12345"
tcp ESTAB  0  0         192.0.2.2:36444 192.0.2.1:12345
```
  At this point, only one connection to the server has been established.
6. On a third terminal, create another endpoint:
```
# ip mptcp endpoint add dev wlp1s0 192.0.2.3 subflow
```
  This command sets the name and IP address of the WiFi interface of the client in this command.
  
  On the monitoring terminal, ip mptcp monitor now logs:
```
[SF_ESTABLISHED] token=63c070d2 remid=0 locid=2 saddr4=192.0.2.3 daddr4=192.0.2.1 sport=53345 dport=12345 backup=0 ifindex=3
```
  The locid field displays the local address ID of the new sub-flow and identifies this sub-flow even if the connection uses network address translation (NAT). The saddr4 field matches the endpoint’s IP address from the ip mptcp endpoint add command.
7. Optional: Display the connections to port 12345 on the server:
```
# ss -taunp | grep ":12345"
tcp ESTAB  0  0         192.0.2.2:36444 192.0.2.1:12345
tcp ESTAB  0  0  192.0.2.3%wlp1s0:53345 192.0.2.1:12345
```
  The command now displays two connections:
  - The connection with source address 192.0.2.2 corresponds to the first MPTCP sub-flow that you established previously.
  - The connection from the sub-flow over the wlp1s0 interface with source address 192.0.2.3.
8. On the third terminal, delete the endpoint:
```
# ip mptcp endpoint delete id 2
```
  Use the ID from the locid field from the ip mptcp monitor output, or retrieve the endpoint ID using the ip mptcp endpoint show command.
  
  On the monitoring terminal, ip mptcp monitor now logs:
```
[     SF_CLOSED] token=63c070d2 remid=0 locid=2 saddr4=192.0.2.3 daddr4=192.0.2.1 sport=53345 dport=12345 backup=0 ifindex=3
```
9. On the first terminal with the nc client, press Ctrl+C to terminate the session.
  
  On the monitoring terminal, ip mptcp monitor now logs:
```
[        CLOSED] token=63c070d2
```

Additional resources

ip-mptcp(1) man page
How NetworkManager manages multiple default gateways

28.6. Disabling Multipath TCP in the kernel

You can explicitly disable the MPTCP option in the kernel.

Procedure

Disable the mptcp.enabled option.

echo "net.mptcp.enabled=0" > /etc/sysctl.d/90-enable-MPTCP.conf

sysctl -p /etc/sysctl.d/90-enable-MPTCP.conf

Verification steps

Verify whether the mptcp.enabled is disabled in the kernel.
```
# sysctl -a | grep mptcp.enabled
net.mptcp.enabled = 0
```

Chapter 29. Configuring the order of DNS servers

Most applications use the getaddrinfo() function of the glibc library to resolve DNS requests. By default, glibc sends all DNS requests to the first DNS server specified in the /etc/resolv.conf file. If this server does not reply, RHEL uses the next server in this file. NetworkManager enables you to influence the order of DNS servers in etc/resolv.conf.

29.1. How NetworkManager orders DNS servers in /etc/resolv.conf

NetworkManager orders DNS servers in the /etc/resolv.conf file based on the following rules:

If only one connection profile exists, NetworkManager uses the order of IPv4 and IPv6 DNS server specified in that connection.
If multiple connection profiles are activated, NetworkManager orders DNS servers based on a DNS priority value. If you set DNS priorities, the behavior of NetworkManager depends on the value set in the dns parameter. You can set this parameter in the [main] section in the /etc/NetworkManager/NetworkManager.conf file:
- dns=default or if the dns parameter is not set:
  
  NetworkManager orders the DNS servers from different connections based on the ipv4.dns-priority and ipv6.dns-priority parameter in each connection.
  
  If you set no value or you set ipv4.dns-priority and ipv6.dns-priority to 0, NetworkManager uses the global default value. See Default values of DNS priority parameters.
- dns=dnsmasq or dns=systemd-resolved:
  
  When you use one of these settings, NetworkManager sets either 127.0.0.1 for dnsmasq or 127.0.0.53 as nameserver entry in the /etc/resolv.conf file.
  
  Both the dnsmasq and systemd-resolved services forward queries for the search domain set in a NetworkManager connection to the DNS server specified in that connection, and forwardes queries to other domains to the connection with the default route. When multiple connections have the same search domain set, dnsmasq and systemd-resolved forward queries for this domain to the DNS server set in the connection with the lowest priority value.

Default values of DNS priority parameters

NetworkManager uses the following default values for connections:

50 for VPN connections
100 for other connections

Valid DNS priority values:

You can set both the global default and connection-specific ipv4.dns-priority and ipv6.dns-priority parameters to a value between -2147483647 and 2147483647.

A lower value has a higher priority.
Negative values have the special effect of excluding other configurations with a greater value. For example, if at least one connection with a negative priority value exists, NetworkManager uses only the DNS servers specified in the connection profile with the lowest priority.
If multiple connections have the same DNS priority, NetworkManager prioritizes the DNS in the following order:
1. VPN connections
2. Connection with an active default route. The active default route is the default route with the lowest metric.

Additional resources

nm-settings(5) man page
Using different DNS servers for different domains

29.2. Setting a NetworkManager-wide default DNS server priority value

NetworkManager uses the following DNS priority default values for connections:

50 for VPN connections
100 for other connections

You can override these system-wide defaults with a custom default value for IPv4 and IPv6 connections.

Procedure

Edit the /etc/NetworkManager/NetworkManager.conf file:
1. Add the [connection] section, if it does not exist:
```
[connection]
```
2. Add the custom default values to the [connection] section. For example, to set the new default for both IPv4 and IPv6 to 200, add:
```
ipv4.dns-priority=200
ipv6.dns-priority=200
```
  You can set the parameters to a value between -2147483647 and 2147483647. Note that setting the parameters to 0 enables the built-in defaults (50 for VPN connections and 100 for other connections).
Reload the NetworkManager service:
```
# systemctl reload NetworkManager
```

Additional resources

NetworkManager.conf(5) man page

29.3. Setting the DNS priority of a NetworkManager connection

If you require a specific order of DNS servers you can set priority values in connection profiles. NetworkManager uses these values to order the servers when the service creates or updates the /etc/resolv.conf file.

Note that setting DNS priorities makes only sense if you have multiple connections with different DNS servers configured. If you have only one connection with multiple DNS servers configured, manually set the DNS servers in the preferred order in the connection profile.

Prerequisites

The system has multiple NetworkManager connections configured.
The system either has no dns parameter set in the /etc/NetworkManager/NetworkManager.conf file or the parameter is set to default.

Procedure

Optionally, display the available connections:

nmcli connection show

NAME UUID TYPE DEVICE Example_con_1 d17ee488-4665-4de2-b28a-48befab0cd43 ethernet enp1s0 Example_con_2 916e4f67-7145-3ffa-9f7b-e7cada8f6bf7 ethernet enp7s0 ...

Set the ipv4.dns-priority and ipv6.dns-priority parameters. For example, to set both parameters to 10 for the Example_con_1 connection:
```
# nmcli connection modify 
Example_con_1
 ipv4.dns-priority 10
 ipv6.dns-priority 10
```
Optionally, repeat the previous step for other connections.
Re-activate the connection you updated:
```
# nmcli connection up 
Example_con_1
```

Verification steps

Display the contents of the /etc/resolv.conf file to verify that the DNS server order is correct:
```
# cat /etc/resolv.conf
```

Chapter 30. Configuring ip networking with ifcfg files

Interface configuration (ifcfg) files control the software interfaces for individual network devices. As the system boots, it uses these files to determine what interfaces to bring up and how to configure them. These files are named ifcfg-name_pass, where the suffix name refers to the name of the device that the configuration file controls. By convention, the ifcfg file’s suffix is the same as the string given by the DEVICE directive in the configuration file itself.

Important

NetworkManager supports profiles stored in the keyfile format. However, by default, NetworkManager uses the ifcfg format when you use the NetworkManager API to create or update profiles.

In a future major RHEL release, the keyfile format will be default. Consider using the keyfile format if you want to manually create and manage configuration files. For details, see Manually creating NetworkManager profiles in keyfile format.

30.1. Configuring an interface with static network settings using ifcfg files

If you do not use the NetworkManager utilities and applications, you can manually configure a network interface by creating ifcfg files.

Procedure

To configure an interface with static network settings using ifcfg files, for an interface with the name enp1s0, create a file with the name ifcfg-enp1s0 in the /etc/sysconfig/network-scripts/ directory that contains:
- For IPv4 configuration:
```
DEVICE=enp1s0
BOOTPROTO=none
ONBOOT=yes
PREFIX=24
IPADDR=10.0.1.27
GATEWAY=10.0.1.1
```
- For IPv6 configuration:
```
DEVICE=enp1s0
BOOTPROTO=none
ONBOOT=yes
IPV6INIT=yes
IPV6ADDR=2001:db8:1::2/64
```

Additional resources

nm-settings-ifcfg-rh(5) man page

30.2. Configuring an interface with dynamic network settings using ifcfg files

If you do not use the NetworkManager utilities and applications, you can manually configure a network interface by creating ifcfg files.

Procedure

To configure an interface named em1 with dynamic network settings using ifcfg files, create a file with the name ifcfg-em1 in the /etc/sysconfig/network-scripts/ directory that contains:
```
DEVICE=em1
BOOTPROTO=dhcp
ONBOOT=yes
```
To configure an interface to send:
- A different host name to the DHCP server, add the following line to the ifcfg file:
```
DHCP_HOSTNAME=hostname
```
- A different fully qualified domain name (FQDN) to the DHCP server, add the following line to the ifcfg file:
```
DHCP_FQDN=fully.qualified.domain.name
```
Note

You can use only one of these settings. If you specify both DHCP_HOSTNAME and DHCP_FQDN, only DHCP_FQDN is used.
To configure an interface to use particular DNS servers, add the following lines to the ifcfg file:
```
  PEERDNS=no
  DNS1=ip-address
  DNS2=ip-address
```
where ip-address is the address of a DNS server. This will cause the network service to update /etc/resolv.conf with the specified DNS servers specified. Only one DNS server address is necessary, the other is optional.

30.3. Managing system-wide and private connection profiles with ifcfg files

By default, all users on a host can use the connections defined in ifcfg files. You can limit this behavior to specific users by adding the USERS parameter to the ifcfg file.

Prerequisite

The ifcfg file already exists.

Procedure

Edit the ifcfg file in the /etc/sysconfig/network-scripts/ directory that you want to limit to certain users, and add:
```
USERS="username1
 username2
 ...
"
```
Reactive the connection:
```
# nmcli connection up connection_name
```

Chapter 31. Using NetworkManager to disable IPv6 for a specific connection

On a system that uses NetworkManager to manage network interfaces, you can disable the IPv6 protocol if the network only uses IPv4. If you disable IPv6, NetworkManager automatically sets the corresponding sysctl values in the Kernel.

Note

If disabling IPv6 using kernel tunables or kernel boot parameters, additional consideration must be given to system configuration. For more information, see the How do I disable or enable the IPv6 protocol in RHEL? article.

31.1. Disabling IPv6 on a connection using nmcli

You can use the nmcli utility to disable the IPv6 protocol on the command line.

Prerequisites

The system uses NetworkManager to manage network interfaces.

Procedure

Optionally, display the list of network connections:

nmcli connection show

NAME UUID TYPE DEVICE Example 7a7e0151-9c18-4e6f-89ee-65bb2d64d365 ethernet enp1s0 ...

Set the ipv6.method parameter of the connection to disabled:

nmcli connection modify

Example

ipv6.method "disabled"

Restart the network connection:
```
# nmcli connection up 
Example
```

Verification steps

Display the IP settings of the device:

ip address show

enp1s0

enp1s0

: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:00:6b:74:be brd ff:ff:ff:ff:ff:ff inet 192.0.2.1/24 brd 192.10.2.255 scope global noprefixroute

enp1s0

valid_lft forever preferred_lft forever

If no inet6 entry is displayed, IPv6 is disabled on the device.

Verify that the /proc/sys/net/ipv6/conf/enp1s0/disable_ipv6 file now contains the value 1:
```
# cat /proc/sys/net/ipv6/conf/
enp1s0
/disable_ipv6
1
```
The value 1 means that IPv6 is disabled for the device.

Chapter 32. Manually configuring the /etc/resolv.conf file

By default, NetworkManager on Red Hat Enterprise Linux (RHEL) 8 dynamically updates the /etc/resolv.conf file with the DNS settings from active NetworkManager connection profiles. However, you can disable this behavior and manually configure DNS settings in /etc/resolv.conf.

Note

Alternatively, if you require a specific order of DNS servers in /etc/resolv.conf, see Configuring the order of DNS servers.

32.1. Disabling DNS processing in the NetworkManager configuration

Procedure

As the root user, create the /etc/NetworkManager/conf.d/90-dns-none.conf file with the following content by using a text editor:
```
[main]
dns=none
```
Reload the NetworkManager service:
```
# systemctl reload NetworkManager
```
Note

After you reload the service, NetworkManager no longer updates the /etc/resolv.conf file. However, the last contents of the file are preserved.
Optionally, remove the Generated by NetworkManager comment from /etc/resolv.conf to avoid confusion.

Verification steps

Edit the /etc/resolv.conf file and manually update the configuration.
Reload the NetworkManager service:
```
# systemctl reload NetworkManager
```
Display the /etc/resolv.conf file:
```
# cat /etc/resolv.conf
```
If you successfully disabled DNS processing, NetworkManager did not override the manually configured settings.

Additional resources

NetworkManager.conf(5) man page
Configuring the order of DNS servers using NetworkManager

32.2. Replacing /etc/resolv.conf with a symbolic link to manually configure DNS settings

By default, NetworkManager manages DNS settings in the /etc/resolv.conf file, and you can configure the order of DNS servers. Alternatively, you can disable DNS processing in NetworkManager if you prefer to manually configure DNS settings in /etc/resolv.conf. For example, NetworkManager does not automatically update the DNS configuration if /etc/resolv.conf is a symbolic link.

Prerequisites

The NetworkManager rc-manager configuration option is not set to file. To verify, use the NetworkManager --print-config command.

Procedure

Create a file, such as /etc/resolv.conf.manually-configured, and add the DNS configuration for your environment to it. Use the same parameters and syntax as in the original /etc/resolv.conf.
Remove the /etc/resolv.conf file:
```
# rm /etc/resolv.conf
```
Create a symbolic link named /etc/resolv.conf that refers to /etc/resolv.conf.manually-configured:
```
# ln -s /etc/resolv.conf.manually-configured /etc/resolv.conf
```

Additional resources

resolv.conf(5) man page
NetworkManager.conf(5) man page
Configuring the order of DNS servers using NetworkManager

Chapter 33. Increasing the ring buffers to reduce a high packet drop rate

Receive ring buffers are shared between the device driver and network interface controller (NIC). The card assigns a transmit (TX) and receive (RX) ring buffer. As the name implies, the ring buffer is a circular buffer where an overflow overwrites existing data. There are two ways to move data from the NIC to the kernel, hardware interrupts and software interrupts, also called SoftIRQs.

The kernel uses the RX ring buffer to store incoming packets until they can be processed by the device driver. The device driver drains the RX ring, typically using SoftIRQs, which puts the incoming packets into a kernel data structure called an sk_buff or skb to begin its journey through the kernel and up to the application which owns the relevant socket.

The kernel uses the TX ring buffer to hold outgoing packets which are destined for the wire. These ring buffers reside at the bottom of the stack and are a crucial point at which packet drop can occur, which in turn will adversely affect network performance.

Increase the size of an Ethernet device’s ring buffers if the packet drop rate causes applications to report a loss of data, timeouts, or other issues.

Procedure

Display the packet drop statistics of the interface:
```
# ethtool -S 
enp1s0

    ...
     rx_queue_0_drops: 97326
     rx_queue_1_drops: 63783
     ...
```
Note that the output of the command depends on the network card and the driver.

High values in counters named discard or drop indicate that the available buffer fills up faster than the kernel can process the packets and tuning the ring buffers is required.

Display the maximum ring buffer sizes:

ethtool -g

enp1s0

Ring parameters for

enp1s0

: Pre-set maximums: RX: 4096 RX Mini: 0 RX Jumbo: 16320 TX: 4096 Current hardware settings: RX: 255 RX Mini: 0 RX Jumbo: 0 TX: 255

If the values in the Pre-set maximums section are higher than in the Current hardware settings section, you can change the settings in the next steps.

Identify the NetworkManager connection profile that uses the interface:

nmcli connection show

NAME UUID TYPE DEVICE

Example-Connection

a5eb6490-cc20-3668-81f8-0314a27f3f75

ethernet

enp1s0

Update the connection profile, and increase the ring buffers:

To increase the RX ring buffer, enter:

nmcli connection modify

Example-Connection

ethtool.ring-rx
4096

To increase the TX ring buffer, enter:

nmcli connection modify

Example-Connection

ethtool.ring-tx
4096

Reload the NetworkManager connection:
```
# nmcli connection up 
Example-Connection
```
Important

Depending on the driver your NIC uses, changing in the ring buffer can shortly interrupt the network connection.

Additional resources

ifconfig and ip commands report packet drops
Should I be concerned about a 0.05% packet drop rate?
ethtool(8) man page

Chapter 34. Configuring 802.3 link settings

34.1. Understanding Auto-negotiation

Auto-negotiation is a feature of the IEEE 802.3u Fast Ethernet protocol. It targets the device ports to provide an optimal performance of speed, duplex mode, and flow control for information exchange over a link. Using the auto-negotiation protocol, you have optimal performance of data transfer over the Ethernet.

Note

To utilize maximum performance of auto-negotiation, use the same configuration on both sides of a link.

34.2. Configuring 802.3 link settings using the nmcli utility

To configure the 802.3 link settings of an Ethernet connection, modify the following configuration parameters:

802-3-ethernet.auto-negotiate
802-3-ethernet.speed
802-3-ethernet.duplex

Procedure

Display the current settings of the connection:

nmcli connection show

Example-connection

... 802-3-ethernet.speed: 0 802-3-ethernet.duplex: -- 802-3-ethernet.auto-negotiate: no ...

You can use these values if you need to reset the parameters in case of any problems.

Set the speed and duplex link settings:

nmcli connection modify

Example-connection

802-3-ethernet.auto-negotiate
no
802-3-ethernet.speed
10000
802-3-ethernet.duplex
full

This command disables auto-negotiation and sets the speed of the connection to 10000 Mbit full duplex.

Reactivate the connection:

nmcli connection up

Example-connection

Verification

Use the ethtool utility to verify the values of Ethernet interface enp1s0:

ethtool enp1s0

Settings for enp1s0: ... Advertised auto-negotiation: No ... Speed: 10000Mb/s Duplex: Full Auto-negotiation: off ... Link detected: yes

Additional resources

Network interface speed is 100Mbps and should be 1Gbps
nm-settings(5) man page

Chapter 35. Configuring ethtool offload features

Network interface cards can use the TCP offload engine (TOE) to offload processing certain operations to the network controller to improve the network throughput.

35.1. Offload features supported by NetworkManager

You can set the following ethtool offload features using NetworkManager:

ethtool.feature-esp-hw-offload
ethtool.feature-esp-tx-csum-hw-offload
ethtool.feature-fcoe-mtu
ethtool.feature-gro
ethtool.feature-gso
ethtool.feature-highdma
ethtool.feature-hw-tc-offload
ethtool.feature-l2-fwd-offload
ethtool.feature-loopback
ethtool.feature-lro
ethtool.feature-macsec-hw-offload
ethtool.feature-ntuple
ethtool.feature-rx
ethtool.feature-rx-all
ethtool.feature-rx-fcs
ethtool.feature-rx-gro-hw
ethtool.feature-rx-gro-list
ethtool.feature-rx-udp_tunnel-port-offload
ethtool.feature-rx-udp-gro-forwarding
ethtool.feature-rx-vlan-filter
ethtool.feature-rx-vlan-stag-filter
ethtool.feature-rx-vlan-stag-hw-parse
ethtool.feature-rxhash
ethtool.feature-rxvlan
ethtool.feature-sg
ethtool.feature-tls-hw-record
ethtool.feature-tls-hw-rx-offload
ethtool.feature-tls-hw-tx-offload
ethtool.feature-tso
ethtool.feature-tx
ethtool.feature-tx-checksum-fcoe-crc
ethtool.feature-tx-checksum-ip-generic
ethtool.feature-tx-checksum-ipv4
ethtool.feature-tx-checksum-ipv6
ethtool.feature-tx-checksum-sctp
ethtool.feature-tx-esp-segmentation
ethtool.feature-tx-fcoe-segmentation
ethtool.feature-tx-gre-csum-segmentation
ethtool.feature-tx-gre-segmentation
ethtool.feature-tx-gso-list
ethtool.feature-tx-gso-partial
ethtool.feature-tx-gso-robust
ethtool.feature-tx-ipxip4-segmentation
ethtool.feature-tx-ipxip6-segmentation
ethtool.feature-tx-nocache-copy
ethtool.feature-tx-scatter-gather
ethtool.feature-tx-scatter-gather-fraglist
ethtool.feature-tx-sctp-segmentation
ethtool.feature-tx-tcp-ecn-segmentation
ethtool.feature-tx-tcp-mangleid-segmentation
ethtool.feature-tx-tcp-segmentation
ethtool.feature-tx-tcp6-segmentation
ethtool.feature-tx-tunnel-remcsum-segmentation
ethtool.feature-tx-udp-segmentation
ethtool.feature-tx-udp_tnl-csum-segmentation
ethtool.feature-tx-udp_tnl-segmentation
ethtool.feature-tx-vlan-stag-hw-insert
ethtool.feature-txvlan

For details about the individual offload features, see the documentation of the ethtool utility and the kernel documentation.

35.2. Configuring an ethtool offload feature using NetworkManager

You can use NetworkManager to enable and disable ethtool offload features in a connection profile.

Procedure

For example, to enable the RX offload feature and disable TX offload in the enp1s0 connection profile, enter:
```
# nmcli con modify 
enp1s0
 ethtool.feature-rx on ethtool.feature-tx off
```
This command explicitly enables RX offload and disables TX offload.
To remove the setting of an offload feature that you previously enabled or disabled, set the feature’s parameter to ignore. For example, to remove the configuration for TX offload, enter:
```
# nmcli con modify 
enp1s0
 ethtool.feature-tx ignore
```
Reactivate the network profile:
```
# nmcli connection up 
enp1s0
```

Verification steps

Use the ethtool -k command to display the current offload features of a network device:
```
# ethtool -k 
network_device
```

Additional resources

Offload features supported by NetworkManager

35.3. Using RHEL System Roles to set ethtool features

You can use the network RHEL System Role to configure ethtool features of a NetworkManager connection.

Important

When you run a play that uses the network RHEL System Role, the system role overrides an existing connection profile with the same name if the value of settings does not match the ones specified in the play. Therefore, always specify the whole configuration of the network connection profile in the play, even if, for example the IP configuration, already exists. Otherwise the role resets these values to their defaults.

Depending on whether it already exists, the procedure creates or updates the enp1s0 connection profile with the following settings:

A static IPv4 address – 198.51.100.20 with a /24 subnet mask
A static IPv6 address – 2001:db8:1::1 with a /64 subnet mask
An IPv4 default gateway – 198.51.100.254
An IPv6 default gateway – 2001:db8:1::fffe
An IPv4 DNS server – 198.51.100.200
An IPv6 DNS server – 2001:db8:1::ffbb
A DNS search domain – example.com
ethtool features:
- Generic receive offload (GRO): disabled
- Generic segmentation offload (GSO): enabled
- TX stream control transmission protocol (SCTP) segmentation: disabled

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on them.
The hosts or host groups on which you want to run this playbook are listed in the Ansible inventory file.

Procedure

Create a playbook file, for example ~/configure-ethernet-device-with-ethtool-features.yml, with the following content:

--- - name: Configure the network hosts:

managed-node-01.example.com

tasks: - name: Configure an Ethernet connection with ethtool features include_role: name: rhel-system-roles.network vars: network_connections: - name: enp1s0 type: ethernet autoconnect: yes ip: address: - 198.51.100.20/24 - 2001:db8:1::1/64 gateway4: 198.51.100.254 gateway6: 2001:db8:1::fffe dns: - 198.51.100.200 - 2001:db8:1::ffbb dns_search: - example.com ethtool: features: gro: "no" gso: "yes" tx_sctp_segmentation: "no" state: up

Run the playbook:

ansible-playbook

~/configure-ethernet-device-with-ethtool-features.yml

Additional resources

/usr/share/ansible/roles/rhel-system-roles.network/README.md file

Chapter 36. Configuring ethtool coalesce settings

Using interrupt coalescing, the system collects network packets and generates a single interrupt for multiple packets. This increases the amount of data sent to the kernel with one hardware interrupt, which reduces the interrupt load, and maximizes the throughput.

36.1. Coalesce settings supported by NetworkManager

You can set the following ethtool coalesce settings using NetworkManager:

coalesce-adaptive-rx
coalesce-adaptive-tx
coalesce-pkt-rate-high
coalesce-pkt-rate-low
coalesce-rx-frames
coalesce-rx-frames-high
coalesce-rx-frames-irq
coalesce-rx-frames-low
coalesce-rx-usecs
coalesce-rx-usecs-high
coalesce-rx-usecs-irq
coalesce-rx-usecs-low
coalesce-sample-interval
coalesce-stats-block-usecs
coalesce-tx-frames
coalesce-tx-frames-high
coalesce-tx-frames-irq
coalesce-tx-frames-low
coalesce-tx-usecs
coalesce-tx-usecs-high
coalesce-tx-usecs-irq
coalesce-tx-usecs-low

36.2. Configuring ethtool coalesce settings using NetworkManager

You can use NetworkManager to set ethtool coalesce settings in connection profiles.

Procedure

For example, to set the maximum number of received packets to delay to 128 in the enp1s0 connection profile, enter:
```
# nmcli connection modify 
enp1s0
 ethtool.coalesce-rx-frames 128
```
To remove a coalesce setting, set the setting to ignore. For example, to remove the ethtool.coalesce-rx-frames setting, enter:
```
# nmcli connection modify 
enp1s0
 ethtool.coalesce-rx-frames ignore
```
To reactivate the network profile:
```
# nmcli connection up 
enp1s0
```

Verification steps

Use the ethtool -c command to display the current offload features of a network device:
```
# ethtool -c 
network_device
```

Additional resources

Coalesce settings supported by NetworkManager

36.3. Using RHEL System Roles to configure ethtool coalesce settings

You can use the network RHEL System Role to configure ethtool coalesce settings of a NetworkManager connection.

Important

When you run a play that uses the network RHEL System Role, the system role overrides an existing connection profile with the same name if the value of settings does not match the ones specified in the play. Therefore, always specify the whole configuration of the network connection profile in the play, even if, for example the IP configuration, already exists. Otherwise the role resets these values to their defaults.

Depending on whether it already exists, the procedure creates or updates the enp1s0 connection profile with the following settings:

A static IPv4 address – 198.51.100.20 with a /24 subnet mask
A static IPv6 address – 2001:db8:1::1 with a /64 subnet mask
An IPv4 default gateway – 198.51.100.254
An IPv6 default gateway – 2001:db8:1::fffe
An IPv4 DNS server – 198.51.100.200
An IPv6 DNS server – 2001:db8:1::ffbb
A DNS search domain – example.com
ethtool coalesce settings:
- RX frames: 128
- TX frames: 128

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on them.
The hosts or host groups on which you want to run this playbook are listed in the Ansible inventory file.

Procedure

Create a playbook file, for example ~/configure-ethernet-device-with-ethtoolcoalesce-settings.yml, with the following content:

---
- name: Configure the network
  hosts: managed-node-01.example.com
  tasks:
  - name: Configure an Ethernet connection with ethtool coalesce settings
    include_role:
      name: rhel-system-roles.network

    vars:
      network_connections:
        - name: enp1s0
          type: ethernet
          autoconnect: yes
          ip:
            address:
              - 198.51.100.20/24
              - 2001:db8:1::1/64
            gateway4: 198.51.100.254
            gateway6: 2001:db8:1::fffe
            dns:
              - 198.51.100.200
              - 2001:db8:1::ffbb
            dns_search:
              - example.com
          ethtool:
            coalesce:
              rx_frames: 128
              tx_frames: 128
          state: up

Run the playbook:

ansible-playbook

~/configure-ethernet-device-with-ethtoolcoalesce-settings.yml

Additional resources

/usr/share/ansible/roles/rhel-system-roles.network/README.md file

Chapter 37. Using MACsec to encrypt layer-2 traffic in the same physical network

You can use MACsec to secure the communication between two devices (point-to-point). For example, your branch office is connected over a Metro-Ethernet connection with the central office, you can configure MACsec on the two hosts that connect the offices to increase the security.

Media Access Control security (MACsec) is a layer 2 protocol that secures different traffic types over the Ethernet links including:

dynamic host configuration protocol (DHCP)
address resolution protocol (ARP)
Internet Protocol version 4 / 6 (IPv4 / IPv6) and
any traffic over IP such as TCP or UDP

MACsec encrypts and authenticates all traffic in LANs, by default with the GCM-AES-128 algorithm, and uses a pre-shared key to establish the connection between the participant hosts. If you want to change the pre-shared key, you need to update the NM configuration on all hosts in the network that uses MACsec.

A MACsec connection uses an Ethernet device, such as an Ethernet network card, VLAN, or tunnel device, as parent. You can either set an IP configuration only on the MACsec device to communicate with other hosts only using the encrypted connection, or you can also set an IP configuration on the parent device. In the latter case, you can use the parent device to communicate with other hosts using an unencrypted connection and the MACsec device for encrypted connections.

MACsec does not require any special hardware. For example, you can use any switch, except if you want to encrypt traffic only between a host and a switch. In this scenario, the switch must also support MACsec.

In other words, there are 2 common methods to configure MACsec;

host to host and
host to switch then switch to other host(s)

Important

You can use MACsec only between hosts that are in the same (physical or virtual) LAN.

37.1. Configuring a MACsec connection using nmcli

You can configure Ethernet interfaces to use MACsec using the nmcli utility. For example, you can create a MACsec connection between two hosts that are connected over Ethernet.

Procedure

On the first host on which you configure MACsec:

Create the connectivity association key (CAK) and connectivity-association key name (CKN) for the pre-shared key:

Create a 16-byte hexadecimal CAK:

# dd if=/dev/urandom count=16 bs=1 2> /dev/null | hexdump -e '1/2 "%04x"'
50b71a8ef0bd5751ea76de6d6c98c03a

Create a 32-byte hexadecimal CKN:

# dd if=/dev/urandom count=32 bs=1 2> /dev/null | hexdump -e '1/2 "%04x"'
f2b4297d39da7330910a74abc0449feb45b5c0b9fc23df1430e1898fcf1c4550

On both hosts you want to connect over a MACsec connection:

Create the MACsec connection:

nmcli connection add type macsec con-name

macsec0

ifname macsec0 connection.autoconnect yes macsec.parent
enp1s0
macsec.mode psk macsec.mka-cak
50b71a8ef0bd5751ea76de6d6c98c03a
macsec.mka-ckn
f2b4297d39da7330910a7abc0449feb45b5c0b9fc23df1430e1898fcf1c4550

Use the CAK and CKN generated in the previous step in the macsec.mka-cak and macsec.mka-ckn parameters. The values must be the same on every host in the MACsec-protected network.

Configure the IP settings on the MACsec connection.
1. Configure the IPv4 settings. For example, to set a static IPv4 address, network mask, default gateway, and DNS server to the macsec0 connection, enter:
```
# nmcli connection modify 
macsec0
 ipv4.method manual ipv4.addresses '192.0.2.1/24
' ipv4.gateway '192.0.2.254
' ipv4.dns '192.0.2.253
'
```
2. Configure the IPv6 settings. For example, to set a static IPv6 address, network mask, default gateway, and DNS server to the macsec0 connection, enter:
```
# nmcli connection modify 
macsec0
 ipv6.method manual ipv6.addresses '2001:db8:1::1/32
' ipv6.gateway '2001:db8:1::fffe
' ipv6.dns '2001:db8:1::fffd
'
```
Activate the connection:
```
# nmcli connection up 
macsec0
```

Verification steps

Verify that the traffic is encrypted:
```
# tcpdump -nn -i 
enp1s0
```
Optional: Display the unencrypted traffic:
```
# tcpdump -nn -i 
macsec0
```
Display MACsec statistics:
```
# ip macsec show
```
Display individual counters for each type of protection: integrity-only (encrypt off) and encryption (encrypt on)
```
# ip -s macsec show
```

37.2. Additional resources

MACsec: a different solution to encrypt network traffic blog.

Chapter 38. Using different DNS servers for different domains

By default, Red Hat Enterprise Linux (RHEL) sends all DNS requests to the first DNS server specified in the /etc/resolv.conf file. If this server does not reply, RHEL uses the next server in this file.

In environments where one DNS server cannot resolve all domains, administrators can configure RHEL to send DNS requests for a specific domain to a selected DNS server. For example, you can configure one DNS server to resolve queries for example.com and another DNS server to resolve queries for example.net. For all other DNS requests, RHEL uses the DNS server configured in the connection with the default gateway.

Important

The systemd-resolved service is provided as a Technology Preview only. Technology Preview features are not supported with Red Hat production Service Level Agreements (SLAs), might not be functionally complete, and Red Hat does not recommend using them for production. These previews provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

See Technology Preview Features Support Scope on the Red Hat Customer Portal for information about the support scope for Technology Preview features.

38.1. Sending DNS requests for a specific domain to a selected DNS server

You can configure systemd-resolved service and NetworkManager to send DNS queries for a specific domain to a selected DNS server.

If you complete the procedure, RHEL uses the DNS service provided by systemd-resolved in the /etc/resolv.conf file. The systemd-resolved service starts a DNS service that listens on port 53 IP address 127.0.0.53. The service dynamically routes DNS requests to the corresponding DNS servers specified in NetworkManager.

Note

The 127.0.0.53 address is only reachable from the local system and not from the network.

Prerequisites

The system has multiple NetworkManager connections configured.
A DNS server and search domain are configured in the NetworkManager connections that are responsible for resolving a specific domain

For example, if the DNS server specified in a VPN connection should resolve queries for the example.com domain, the VPN connection profile must have:
- Configured a DNS server that can resolve example.com
- Configured the search domain to example.com in the ipv4.dns-search and ipv6.dns-search parameters

Procedure

Start and enable the systemd-resolved service:
```
# systemctl --now enable systemd-resolved
```
Edit the /etc/NetworkManager/NetworkManager.conf file, and set the following entry in the [main] section:
```
dns=systemd-resolved
```
Reload the NetworkManager service:
```
# systemctl reload NetworkManager
```

Verification steps

Verify that the nameserver entry in the /etc/resolv.conf file refers to 127.0.0.53:
```
# cat /etc/resolv.conf
nameserver 127.0.0.53
```

Verify that the systemd-resolved service listens on port 53 on the local IP address 127.0.0.53:

# ss -tulpn | grep "127.0.0.53"
udp  UNCONN 0  0      127.0.0.53%lo:53   0.0.0.0:*    users:(("systemd-resolve",pid=1050
,fd=12))
tcp  LISTEN 0  4096   127.0.0.53%lo:53   0.0.0.0:*    users:(("systemd-resolve",pid=1050
,fd=13
))

Additional resources

NetworkManager.conf(5) man page

Chapter 39. Getting started with IPVLAN

IPVLAN is a driver for a virtual network device that can be used in container environment to access the host network. IPVLAN exposes a single MAC address to the external network regardless the number of IPVLAN device created inside the host network. This means that a user can have multiple IPVLAN devices in multiple containers and the corresponding switch reads a single MAC address. IPVLAN driver is useful when the local switch imposes constraints on the total number of MAC addresses that it can manage.

39.1. IPVLAN modes

The following modes are available for IPVLAN:

L2 mode

In IPVLAN L2 mode, virtual devices receive and respond to address resolution protocol (ARP) requests. The netfilter framework runs only inside the container that owns the virtual device. No netfilter chains are executed in the default namespace on the containerized traffic. Using L2 mode provides good performance, but less control on the network traffic.
L3 mode

In L3 mode, virtual devices process only L3 traffic and above. Virtual devices do not respond to ARP request and users must configure the neighbour entries for the IPVLAN IP addresses on the relevant peers manually. The egress traffic of a relevant container is landed on the netfilter POSTROUTING and OUTPUT chains in the default namespace while the ingress traffic is threaded in the same way as L2 mode. Using L3 mode provides good control but decreases the network traffic performance.
L3S mode

In L3S mode, virtual devices process the same way as in L3 mode, except that both egress and ingress traffics of a relevant container are landed on netfilter chain in the default namespace. L3S mode behaves in a similar way to L3 mode but provides greater control of the network.

Note

The IPVLAN virtual device does not receive broadcast and multicast traffic in case of L3 and L3S modes.

39.2. Comparison of IPVLAN and MACVLAN

The following table shows the major differences between MACVLAN and IPVLAN.

MACVLANIPVLAN

Uses MAC address for each MACVLAN device. The overlimit of MAC addresses of MAC table in switch might cause loosing the connectivity.

Uses single MAC address which does not limit the number of IPVLAN devices.

Netfilter rules for global namespace cannot affect traffic to or from MACVLAN device in a child namespace.

It is possible to control traffic to or from IPVLAN device in L3 mode and L3S mode.

Note that both IPVLAN and MACVLAN do not require any level of encapsulation.

39.3. Creating and configuring the IPVLAN device using iproute2

This procedure shows how to set up the IPVLAN device using iproute2.

Procedure

To create an IPVLAN device, enter the following command:

ip link add link

real_NIC_device

name
IPVLAN_device
type ipvlan mode l2

Note that network interface controller (NIC) is a hardware component which connects a computer to a network.

Example 39.1. Creating an IPVLAN device

ip link add link enp0s31f6 name my_ipvlan type ipvlan mode l2

ip link

47: my_ipvlan@enp0s31f6: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000 link/ether e8:6a:6e:8a:a2:44 brd ff:ff:ff:ff:ff:ff

To assign an IPv4 or IPv6 address to the interface, enter the following command:
```
# ip addr add dev 
IPVLAN_device
 IP_address/subnet_mask_prefix
```
In case of configuring an IPVLAN device in L3 mode or L3S mode, make the following setups:
1. Configure the neighbor setup for the remote peer on the remote host:
```
# ip neigh add dev 
peer_device
 IPVLAN_device_IP_address
 lladdr MAC_address
```
  where MAC_address is the MAC address of the real NIC on which an IPVLAN device is based on.
2. Configure an IPVLAN device for L3 mode with the following command:
```
# ip route add dev 
<real_NIC_device>
 <peer_IP_address/32>
```
  For L3S mode:
```
# ip route add dev 
real_NIC_device
 peer_IP_address/32
```
  where IP-address represents the address of the remote peer.
To set an IPVLAN device active, enter the following command:
```
# ip link set dev 
IPVLAN_device
 up
```
To check if the IPVLAN device is active, execute the following command on the remote host:
```
# ping 
IP_address
```
where the IP_address uses the IP address of the IPVLAN device.

Chapter 40. Reusing the same IP address on different interfaces

With Virtual routing and forwarding (VRF), administrators can use multiple routing tables simultaneously on the same host. For that, VRF partitions a network at layer 3. This enables the administrator to isolate traffic using separate and independent route tables per VRF domain. This technique is similar to virtual LANs (VLAN), which partitions a network at layer 2, where the operating system uses different VLAN tags to isolate traffic sharing the same physical medium.

One benefit of VRF over partitioning on layer 2 is that routing scales better considering the number of peers involved.

Red Hat Enterprise Linux uses a virtual vrt device for each VRF domain and adds routes to a VRF domain by adding existing network devices to a VRF device. Addresses and routes previously attached to the original device will be moved inside the VRF domain.

Note that each VRF domain is isolated from each other.

40.1. Permanently reusing the same IP address on different interfaces

You can use the virtual routing and forwarding (VRF) feature to permanently use the same IP address on different interfaces in one server.

Important

To enable remote peers to contact both VRF interfaces while reusing the same IP address, the network interfaces must belong to different broadcasting domains. A broadcast domain in a network is a set of nodes, which receive broadcast traffic sent by any of them. In most configurations, all nodes connected to the same switch belong to the same broadcasting domain.

Prerequisites

You are logged in as the root user.
The network interfaces are not configured.

Procedure

Create and configure the first VRF device:
1. Create a connection for the VRF device and assign it to a routing table. For example, to create a VRF device named vrf0 that is assigned to the 1001 routing table:
```
# nmcli connection add type vrf ifname 
vrf0
 con-name vrf0
 table 1001 ipv4.method disabled ipv6.method disabled
```
2. Enable the vrf0 device:
```
# nmcli connection up 
vrf0
```
3. Assign a network device to the VRF just created. For example, to add the enp1s0 Ethernet device to the vrf0 VRF device and assign an IP address and the subnet mask to enp1s0, enter:
```
# nmcli connection add type ethernet con-name 
vrf.enp1s0
 ifname enp1s0
 master vrf0 ipv4.method manual
 ipv4.address 192.0.2.1/24
```
4. Activate the vrf.enp1s0 connection:
```
# nmcli connection up 
vrf.enp1s0
```
Create and configure the next VRF device:
1. Create the VRF device and assign it to a routing table. For example, to create a VRF device named vrf1 that is assigned to the 1002 routing table, enter:
```
# nmcli connection add type vrf ifname 
vrf1
 con-name vrf1
 table 1002 ipv4.method disabled ipv6.method disabled
```
2. Activate the vrf1 device:
```
# nmcli connection up 
vrf1
```
3. Assign a network device to the VRF just created. For example, to add the enp7s0 Ethernet device to the vrf1 VRF device and assign an IP address and the subnet mask to enp7s0, enter:
```
# nmcli connection add type ethernet con-name 
vrf.enp7s0
 ifname enp7s0
 master vrf1
 ipv4.method manual
 ipv4.address 192.0.2.1/24
```
4. Activate the vrf.enp7s0 device:
```
# nmcli connection up 
vrf.enp7s0
```

40.2. Temporarily reusing the same IP address on different interfaces

You can use the virtual routing and forwarding (VRF) feature to temporarily use the same IP address on different interfaces in one server. Use this procedure only for testing purposes, because the configuration is temporary and lost after you reboot the system.

Important

To enable remote peers to contact both VRF interfaces while reusing the same IP address, the network interfaces must belong to different broadcasting domains. A broadcast domain in a network is a set of nodes which receive broadcast traffic sent by any of them. In most configurations, all nodes connected to the same switch belong to the same broadcasting domain.

Prerequisites

You are logged in as the root user.
The network interfaces are not configured.

Procedure

Create and configure the first VRF device:
1. Create the VRF device and assign it to a routing table. For example, to create a VRF device named blue that is assigned to the 1001 routing table:
```
# ip link add dev blue type vrf table 1001
```
2. Enable the blue device:
```
# ip link set dev blue up
```
3. Assign a network device to the VRF device. For example, to add the enp1s0 Ethernet device to the blue VRF device:
```
# ip link set dev enp1s0 master blue
```
4. Enable the enp1s0 device:
```
# ip link set dev enp1s0 up
```
5. Assign an IP address and subnet mask to the enp1s0 device. For example, to set it to 192.0.2.1/24:
```
# ip addr add dev enp1s0 192.0.2.1/24
```
Create and configure the next VRF device:
1. Create the VRF device and assign it to a routing table. For example, to create a VRF device named red that is assigned to the 1002 routing table:
```
# ip link add dev red type vrf table 1002
```
2. Enable the red device:
```
# ip link set dev red up
```
3. Assign a network device to the VRF device. For example, to add the enp7s0 Ethernet device to the red VRF device:
```
# ip link set dev enp7s0 master red
```
4. Enable the enp7s0 device:
```
# ip link set dev enp7s0 up
```
5. Assign the same IP address and subnet mask to the enp7s0 device as you used for enp1s0 in the blue VRF domain:
```
# ip addr add dev enp7s0 192.0.2.1/24
```
Optionally, create further VRF devices as described above.

40.3. Additional resources

/usr/share/doc/kernel-doc-< kernel_version
>/Documentation/networking/vrf.txt from the kernel-doc package

Chapter 41. Starting a service within an isolated VRF network

With virtual routing and forwarding (VRF), you can create isolated networks with a routing table that is different to the main routing table of the operating system. You can then start services and applications so that they have only access to the network defined in that routing table.

41.1. Configuring a VRF device

To use virtual routing and forwarding (VRF), you create a VRF device and attach a physical or virtual network interface and routing information to it.

Warning

To prevent that you lock out yourself out remotely, perform this procedure on the local console or remotely over a network interface that you do not want to assign to the VRF device.

Prerequisites

You are logged in locally or using a network interface that is different to the one you want to assign to the VRF device.

Procedure

Create the vrf0 connection with a same-named virtual device, and attach it to routing table 1000:

nmcli connection add type vrf ifname

vrf0

con-name
vrf0
table
1000
ipv4.method disabled ipv6.method disabled

Add the enp1s0 device to the vrf0 connection, and configure the IP settings:
```
# nmcli connection add type ethernet con-name 
enp1s0
 ifname enp1s0
 master vrf0
 ipv4.method manual
 ipv4.address 192.0.2.1/24
 ipv4.gateway 192.0.2.254
```
This command creates the enp1s0 connection as a port of the vrf0 connection. Due to this configuration, the routing information are automatically assigned to the routing table 1000 that is associated with the vrf0 device.
If you require static routes in the isolated network:
1. Add the static routes:
```
# nmcli connection modify 
enp1s0
 +ipv4.routes "198.51.100.0/24
 192.0.2.2
"
```
  This adds a route to the 198.51.100.0/24 network that uses 192.0.2.2 as the router.
2. Activate the connection:
```
# nmcli connection up 
enp1s0
```

Verification

Display the IP settings of the device that is associated with vrf0:

ip -br addr show vrf

vrf0

enp1s0

192.0.2.15/24

Display the VRF devices and their associated routing table:

ip vrf show

Name Table -----------------------

vrf0

1000

Display the main routing table:

# ip route show
default via 192.168.0.1
 dev enp1s0
 proto static metric 100

Display the routing table 1000:

# ip route show table 
1000

default via 192.0.2.254
 dev enp1s0 proto static metric 101
broadcast 192.0.2.0
 dev enp1s0
 proto kernel scope link src 192.0.2.1
192.0.2.0
/24 dev enp1s0
 proto kernel scope link src 192.0.2.1 metric 101
local 192.0.2.1
 dev enp1s0
 proto kernel scope host src 192.0.2.1
broadcast 192.0.2.255
 dev enp1s0
 proto kernel scope link src 192.0.2.1
198.51.100.0/24
 via 192.0.2.2
 dev enp1s0
 proto static metric 101

The default entry indicates that services that use this routing table, use 192.0.2.254 as their default gateway and not the default gateway in the main routing table.

Execute the traceroute utility in the network associated with vrf0 to verify that the utility uses the route from table 1000:
```
# ip vrf exec 
vrf0
 traceroute 203.0.113.1
traceroute to 203.0.113.1
 (203.0.113.1), 30 hops max, 60 byte packets
 1  192.0.2.254
 (192.0.2.254)  0.516 ms  0.459 ms  0.430 ms
...
```
The first hop is the default gateway that is assigned to the routing table 1000 and not the default gateway from the system’s main routing table.

Additional resources

ip-vrf(8) man page

41.2. Starting a service within an isolated VRF network

You can configure a service, such as the Apache HTTP Server, to start within an isolated virtual routing and forwarding (VRF) network.

Important

Services can only bind to local IP addresses that are in the same VRF network.

Prerequisites

You configured the vrf0 device.
You configured Apache HTTP Server to listen only on the IP address that is assigned to the interface associated with the vrf0 device.

Procedure

Display the content of the httpd systemd service:
```
# systemctl cat httpd
...
[Service]
ExecStart=/usr/sbin/httpd $OPTIONS -DFOREGROUND
...
```
You require the content of the ExecStart parameter in a later step to run the same command within the isolated VRF network.
Create the /etc/systemd/system/httpd.service.d/ directory:
```
# mkdir /etc/systemd/system/httpd.service.d/
```
Create the /etc/systemd/system/httpd.service.d/override.conf file with the following content:
```
[Service]
ExecStart=
ExecStart=/usr/sbin/ip vrf exec vrf0
 /usr/sbin/httpd $OPTIONS -DFOREGROUND
```
To override the ExecStart parameter, you first need to unset it and then set it to the new value as shown.
Reload systemd.
```
# systemctl daemon-reload
```
Restart the httpd service.
```
# systemctl restart httpd
```

Verification

Display the process IDs (PID) of httpd processes:
```
# pidof -c httpd
1904 ...
```
Display the VRF association for the PIDs, for example:
```
# ip vrf identify 1904
vrf0
```
Display all PIDs associated with the vrf0 device:
```
# ip vrf pids vrf0
1904  httpd
...
```

Additional resources

ip-vrf(8) man page

Chapter 42. Running dhclient exit hooks using NetworkManager a dispatcher script

You can use a NetworkManager dispatcher script to execute dhclient exit hooks.

42.1. The concept of NetworkManager dispatcher scripts

The NetworkManager-dispatcher service executes user-provided scripts in alphabetical order when network events happen. These scripts are typically shell scripts, but can be any executable script or application. You can use dispatcher scripts, for example, to adjust network-related settings that you cannot manage with NetworkManager.

You can store dispatcher scripts in the following directories:

/etc/NetworkManager/dispatcher.d/: The general location for dispatcher scripts the root user can edit.
/usr/lib/NetworkManager/dispatcher.d/: For pre-deployed immutable dispatcher scripts.

For security reasons, the NetworkManager-dispatcher service executes scripts only if the following conditions met:

The script is owned by the root user.
The script is only readable and writable by root.
The setuid bit is not set on the script.

The NetworkManager-dispatcher service runs each script with two arguments:

The interface name of the device the operation happened on.
The action, such as up, when the interface has been activated.

The Dispatcher scripts section in the NetworkManager(8) man page provides an overview of actions and environment variables you can use in scripts.

The NetworkManager-dispatcher service runs one script at a time, but asynchronously from the main NetworkManager process. Note that, if a script is queued, the service will always run it, even if a later event makes it obsolete. However, the NetworkManager-dispatcher service runs scripts that are symbolic links referring to files in /etc/NetworkManager/dispatcher.d/no-wait.d/ immediately, without waiting for the termination of previous scripts, and in parallel.

Additional resources

NetworkManager(8) man page

42.2. Creating a NetworkManager dispatcher script that runs dhclient exit hooks

When a DHCP server assigns or updates an IPv4 address, NetworkManager can run a dispatcher script stored in the /etc/dhcp/dhclient-exit-hooks.d/ directory. This dispatcher script can then, for example, run dhclient exit hooks.

Prerequisites

The dhclient exit hooks are stored in the /etc/dhcp/dhclient-exit-hooks.d/ directory.

Procedure

Create the /etc/NetworkManager/dispatcher.d/12-dhclient-down file with the following content:

#!/bin/bash
# Run dhclient.exit-hooks.d scripts

if [ -n "$DHCP4_DHCP_LEASE_TIME" ] ; then
  if [ "$2" = "dhcp4-change" ] || [ "$2" = "up" ] ; then
    if [ -d /etc/dhcp/dhclient-exit-hooks.d ] ; then
      for f in /etc/dhcp/dhclient-exit-hooks.d/*.sh ; do
        if [ -x "${f}" ]; then
          . "${f}"
        fi
      done
    fi
  fi
fi

Set the root user as owner of the file:

# chown root:root

/etc/NetworkManager/dispatcher.d/12-dhclient-down

Set the permissions so that only the root user can execute it:

chmod 0700

/etc/NetworkManager/dispatcher.d/12-dhclient-down

Restore the SELinux context:

restorecon

/etc/NetworkManager/dispatcher.d/12-dhclient-down

Additional resources

NetworkManager(8) man page

Chapter 43. Introduction to NetworkManager Debugging

Increasing the log levels for all or certain domains helps to log more details of the operations NetworkManager performs. Administrators can use this information to troubleshoot problems. NetworkManager provides different levels and domains to produce logging information. The /etc/NetworkManager/NetworkManager.conf file is the main configuration file for NetworkManager. The logs are stored in the journal.

43.1. Debugging levels and domains

You can use the levels and domains parameters to manage the debugging for NetworkManager. The level defines the verbosity level, whereas the domains define the category of the messages to record the logs with given severity (level).

Log levelsDescription

OFF

Does not log any messages about NetworkManager

ERR

Logs only critical errors

WARN

Logs warnings that can reflect the operation

INFO

Logs various informational messages that are useful for tracking state and operations

DEBUG

Enables verbose logging for debugging purposes

TRACE

Enables more verbose logging than the DEBUG level

Note that subsequent levels log all messages from earlier levels. For example, setting the log level to INFO also logs messages contained in the ERR and WARN log level.

Additional resources

NetworkManager.conf(5) man page

43.2. Setting the NetworkManager log level

By default, all the log domains are set to record the INFO log level. Disable rate-limiting before collecting debug logs. With rate-limiting, systemd-journald drops messages if there are too many of them in a short time. This can occur when the log level is TRACE.

This procedure disables rate-limiting and enables recording debug logs for the all (ALL) domains.

Procedure

To disable rate-limiting, edit the /etc/systemd/journald.conf file, uncomment the RateLimitBurst parameter in the [Journal] section, and set its value as 0:
```
RateLimitBurst=0
```
Restart the systemd-journald service.
```
# systemctl restart systemd-journald
```
Create the /etc/NetworkManager/conf.d/95-nm-debug.conf file with the following content:
```
[logging]
domains=ALL:TRACE
```
The domains parameter can contain multiple comma-separated domain:level pairs.
Restart the NetworkManager service.
```
# systemctl restart NetworkManager
```

Verification

Query the systemd journal to display the journal entries of the NetworkManager unit:

# journalctl -u NetworkManager
...
Jun 30 15:24:32 server NetworkManager[164187]: <debug> [1656595472.4939] active-connection[0x5565143c80a0]: update activation type from assume to managed
Jun 30 15:24:32 server NetworkManager[164187]: <trace> [1656595472.4939] device[55b33c3bdb72840c] (enp1s0): sys-iface-state: assume -> managed
Jun 30 15:24:32 server NetworkManager[164187]: <trace> [1656595472.4939] l3cfg[4281fdf43e356454,ifindex=3]: commit type register (type "update", source "device", existing a369f23014b9ede3) -> a369f23014b9ede3
Jun 30 15:24:32 server NetworkManager[164187]: <info>  [1656595472.4940] manager: NetworkManager state is now CONNECTED_SITE
...

43.3. Temporarily setting log levels at run time using nmcli

You can change the log level at run time using nmcli. However, Red Hat recommends to enable debugging using configuration files and restart NetworkManager. Updating debugging levels and domains using the .conf file helps to debug boot issues and captures all the logs from the initial state.

Procedure

Optional: Display the current logging settings:

nmcli general logging

LEVEL DOMAINS INFO PLATFORM,RFKILL,ETHER,WIFI,BT,MB,DHCP4,DHCP6,PPP,WIFI_SCAN,IP4,IP6,A UTOIP4,DNS,VPN,SHARING,SUPPLICANT,AGENTS,SETTINGS,SUSPEND,CORE,DEVICE,OLPC, WIMAX,INFINIBAND,FIREWALL,ADSL,BOND,VLAN,BRIDGE,DBUS_PROPS,TEAM,CONCHECK,DC B,DISPATCH

To modify the logging level and domains, use the following options:
- To set the log level for all domains to the same LEVEL, enter:
```
# nmcli general logging level 
LEVEL
 domains ALL
```
- To change the level for specific domains, enter:
```
# nmcli general logging level 
LEVEL
 domains DOMAINS
```
  Note that updating the logging level using this command disables logging for all the other domains.
- To change the level of specific domains and preserve the level of all other domains, enter:
```
# nmcli general logging level KEEP domains 
DOMAIN:LEVEL
,DOMAIN:LEVEL
```

43.4. Viewing NetworkManager logs

You can view the NetworkManager logs for troubleshooting.

Procedure

To view the logs, enter:
```
# journalctl -u NetworkManager -b
```

Additional resources

NetworkManager.conf(5) man page
journalctl(1) man page

Chapter 44. Introduction to Nmstate

Nmstate is a declarative network manager API. The nmstate package provides the libnmstate Python library and a command-line utility, nmstatectl, to manage NetworkManager on RHEL. When you use Nmstate, you describe the expected networking state using YAML or JSON-formatted instructions.

Nmstate has many benefits. For example, it:

Provides a stable and extensible interface to manage RHEL network capabilities
Supports atomic and transactional operations at the host and cluster level
Supports partial editing of most properties and preserves existing settings that are not specified in the instructions
Provides plug-in support to enable administrators to use their own plug-ins

44.1. Using the libnmstate library in a Python application

The libnmstate Python library enables developers to use Nmstate in their own application

To use the library, import it in your source code:

import libnmstate

Note that you must install the nmstate package to use this library.

Example 44.1. Querying the network state using the libnmstate library

The following Python code imports the libnmstate library and displays the available network interfaces and their state:

import json
import libnmstate
from libnmstate.schema import Interface

net_state = libnmstate.show()
for iface_state in net_state[Interface.KEY]:
    print(iface_state[Interface.NAME] + ": "
          + iface_state[Interface.STATE])

44.2. Updating the current network configuration using nmstatectl

You can use the nmstatectl utility to store the current network configuration of one or all interfaces in a file. You can then use this file to:

Modify the configuration and apply it to the same system.
Copy the file to a different host and configure the host with the same or modified settings.

For example, you can export the settings of the enp1s0 interface to a file, modify the configuration, and apply the settings to the host.

Prerequisites

The nmstate package is installed.

Procedure

Export the settings of the enp1s0 interface to the ~/network-config.yml file:
```
# nmstatectl show 
enp1s0
 > ~/network-config.yml
```
This command stores the configuration of enp1s0 in YAML format. To store the output in JSON format, pass the --json option to the command.

If you do not specify an interface name, nmstatectl exports the configuration of all interfaces.
Modify the ~/network-config.yml file using a text editor to update the configuration.
Apply the settings from the ~/network-config.yml file:
```
# nmstatectl apply 
~/network-config.yml
```
If you exported the settings in JSON format, pass the --json option to the command.

44.3. Network states for the network RHEL System role

The network RHEL system role supports state configurations in playbooks to configure the devices. For this, use the network_state variable followed by the state configurations.

Benefits of using the network_state variable in a playbook:

Using the declarative method with the state configurations, you can configure interfaces, and the NetworkManager creates a profile for these interfaces in the background.
With the network_state variable, you can specify the options that you require to change, and all the other options will remain the same as they are. However, with the network_connections variable, you must specify all settings to change the network connection profile.

For example, to create an Ethernet connection with dynamic IP address settings, use the following vars block in your playbook:

Playbook with state configurations

Regular playbook

vars:
  network_state:
    interfaces:
    - name: enp7s0
      type: ethernet
      state: up
      ipv4:
        enabled: true
        auto-dns: true
        auto-gateway: true
        auto-routes: true
        dhcp: true
      ipv6:
        enabled: true
        auto-dns: true
        auto-gateway: true
        auto-routes: true
        autoconf: true
        dhcp: true

vars:
  network_connections:
    - name: enp7s0
      interface_name: enp7s0
      type: ethernet
      autoconnect: yes
      ip:
        dhcp4: yes
        auto6: yes
      state: up

For example, to only change the connection status of dynamic IP address settings that you created as above, use the following vars block in your playbook:

Playbook with state configurations

Regular playbook

vars:
  network_state:
    interfaces:
    - name: enp7s0
      type: ethernet
      state: down

vars:
  network_connections:
    - name: enp7s0
      interface_name: enp7s0
      type: ethernet
      autoconnect: yes
      ip:
        dhcp4: yes
        auto6: yes
      state: down

Additional resources

/usr/share/ansible/roles/rhel-system-roles.network/README.md file
Introduction to Nmstate

44.4. Additional resources

/usr/share/doc/nmstate/README.md
/usr/share/doc/nmstate/examples/

Chapter 45. Capturing network packets

To debug network issues and communications, you can capture network packets. The following sections provide instructions and additional information about capturing network packets.

45.1. Using xdpdump to capture network packets including packets dropped by XDP programs

The xdpdump utility captures network packets. Unlike the tcpdump utility, xdpdump uses an extended Berkeley Packet Filter(eBPF) program for this task. This enables xdpdump to also capture packets dropped by Express Data Path (XDP) programs. User-space utilities, such as tcpdump, are not able to capture these dropped packages, as well as original packets modified by an XDP program.

You can use xdpdump to debug XDP programs that are already attached to an interface. Therefore, the utility can capture packets before an XDP program is started and after it has finished. In the latter case, xdpdump also captures the XDP action. By default, xdpdump captures incoming packets at the entry of the XDP program.

Important

On other architectures than AMD and Intel 64-bit, the xdpdump utility is provided as a Technology Preview only. Technology Preview features are not supported with Red Hat production Service Level Agreements (SLAs), might not be functionally complete, and Red Hat does not recommend using them for production. These previews provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

See Technology Preview Features Support Scope on the Red Hat Customer Portal for information about the support scope for Technology Preview features.

Note that xdpdump has no packet filter or decode capabilities. However, you can use it in combination with tcpdump for packet decoding.

Prerequisites

A network driver that supports XDP programs.
An XDP program is loaded to the enp1s0 interface. If no program is loaded, xdpdump captures packets in a similar way tcpdump does, for backward compatibility.

Procedure

To capture packets on the enp1s0 interface and write them to the /root/capture.pcap file, enter:
```
# xdpdump -i enp1s0 -w /root/capture.pcap
```
To stop capturing packets, press

Ctrl

+

C

.

Additional resources

xdpdump(8) man page
If you are a developer and you are interested in the source code of xdpdump, download and install the corresponding source RPM (SRPM) from the Red Hat Customer Portal.

45.2. Additional resources

How to capture network packets with tcpdump?

Chapter 46. Using and configuring firewalld

A firewall is a way to protect machines from any unwanted traffic from outside. It enables users to control incoming network traffic on host machines by defining a set of firewall rules. These rules are used to sort the incoming traffic and either block it or allow through.

firewalld is a firewall service daemon that provides a dynamic customizable host-based firewall with a D-Bus interface. Being dynamic, it enables creating, changing, and deleting the rules without the necessity to restart the firewall daemon each time the rules are changed.

firewalld uses the concepts of zones and services, that simplify the traffic management. Zones are predefined sets of rules. Network interfaces and sources can be assigned to a zone. The traffic allowed depends on the network your computer is connected to and the security level this network is assigned. Firewall services are predefined rules that cover all necessary settings to allow incoming traffic for a specific service and they apply within a zone.

Services use one or more ports or addresses for network communication. Firewalls filter communication based on ports. To allow network traffic for a service, its ports must be open. firewalld blocks all traffic on ports that are not explicitly set as open. Some zones, such as trusted, allow all traffic by default.

Note that firewalld with nftables backend does not support passing custom nftables rules to firewalld, using the --direct option.

46.1. Getting started with `firewalld`

The following is an introduction to firewalld features, such as services and zones, and how to manage the firewalld systemd service.

46.1.1. When to use firewalld, nftables, or iptables

The following is a brief overview in which scenario you should use one of the following utilities:

firewalld: Use the firewalld utility for simple firewall use cases. The utility is easy to use and covers the typical use cases for these scenarios.
nftables: Use the nftables utility to set up complex and performance-critical firewalls, such as for a whole network.
iptables: The iptables utility on Red Hat Enterprise Linux uses the nf_tables kernel API instead of the legacy back end. The nf_tables API provides backward compatibility so that scripts that use iptables commands still work on Red Hat Enterprise Linux. For new firewall scripts, Red Hat recommends to use nftables.

Important

To prevent the different firewall services from influencing each other, run only one of them on a RHEL host, and disable the other services.

46.1.2. Zones

⁠firewalld can be used to separate networks into different zones according to the level of trust that the user has decided to place on the interfaces and traffic within that network. A connection can only be part of one zone, but a zone can be used for many network connections.

NetworkManager notifies firewalld of the zone of an interface. You can assign zones to interfaces with:

NetworkManager
firewall-config tool
firewall-cmd command-line tool
The RHEL web console

The latter three can only edit the appropriate NetworkManager configuration files. If you change the zone of the interface using the web console, firewall-cmd or firewall-config, the request is forwarded to NetworkManager and is not handled by ⁠firewalld.

The predefined zones are stored in the /usr/lib/firewalld/zones/ directory and can be instantly applied to any available network interface. These files are copied to the /etc/firewalld/zones/ directory only after they are modified. The default settings of the predefined zones are as follows:

block: Any incoming network connections are rejected with an icmp-host-prohibited message for IPv4 and icmp6-adm-prohibited for IPv6. Only network connections initiated from within the system are possible.
dmz: For computers in your demilitarized zone that are publicly-accessible with limited access to your internal network. Only selected incoming connections are accepted.
drop: Any incoming network packets are dropped without any notification. Only outgoing network connections are possible.
external: For use on external networks with masquerading enabled, especially for routers. You do not trust the other computers on the network to not harm your computer. Only selected incoming connections are accepted.
home: For use at home when you mostly trust the other computers on the network. Only selected incoming connections are accepted.
internal: For use on internal networks when you mostly trust the other computers on the network. Only selected incoming connections are accepted.
public: For use in public areas where you do not trust other computers on the network. Only selected incoming connections are accepted.
trusted: All network connections are accepted.
work: For use at work where you mostly trust the other computers on the network. Only selected incoming connections are accepted.

One of these zones is set as the default zone. When interface connections are added to NetworkManager, they are assigned to the default zone. On installation, the default zone in firewalld is set to be the public zone. The default zone can be changed.

Note

The network zone names should be self-explanatory and to allow users to quickly make a reasonable decision. To avoid any security problems, review the default zone configuration and disable any unnecessary services according to your needs and risk assessments.

Additional resources

The firewalld.zone(5) man page.

46.1.3. Predefined services

A service can be a list of local ports, protocols, source ports, and destinations, as well as a list of firewall helper modules automatically loaded if a service is enabled. Using services saves users time because they can achieve several tasks, such as opening ports, defining protocols, enabling packet forwarding and more, in a single step, rather than setting up everything one after another.

Service configuration options and generic file information are described in the firewalld.service(5) man page. The services are specified by means of individual XML configuration files, which are named in the following format: service-name.xml. Protocol names are preferred over service or application names in firewalld.

Services can be added and removed using the graphical firewall-config tool, firewall-cmd, and firewall-offline-cmd.

Alternatively, you can edit the XML files in the /etc/firewalld/services/ directory. If a service is not added or changed by the user, then no corresponding XML file is found in /etc/firewalld/services/. The files in the /usr/lib/firewalld/services/ directory can be used as templates if you want to add or change a service.

Additional resources

The firewalld.service(5) man page

46.1.4. Starting firewalld

Procedure

To start firewalld, enter the following command as root:

# systemctl unmask firewalld
# systemctl start firewalld

To ensure firewalld starts automatically at system start, enter the following command as root:
```
# systemctl enable firewalld
```

46.1.5. Stopping firewalld

Procedure

To stop firewalld, enter the following command as root:
```
# systemctl stop firewalld
```
To prevent firewalld from starting automatically at system start:
```
# systemctl disable firewalld
```
To make sure firewalld is not started by accessing the firewalld D-Bus interface and also if other services require firewalld:
```
# systemctl mask firewalld
```

46.1.6. Verifying the permanent firewalld configuration

In certain situations, for example after manually editing firewalld configuration files, administrators want to verify that the changes are correct. You can use the firewall-cmd utility to verify the configuration.

Prerequisites

The firewalld service is running.

Procedure

Verify the permanent configuration of the firewalld service:
```
# firewall-cmd --check-config
success
```
If the permanent configuration is valid, the command returns success. In other cases, the command returns an error with further details, such as the following:
```
# firewall-cmd --check-config
Error: INVALID_PROTOCOL: 'public.xml': 'tcpx' not from {'tcp'|'udp'|'sctp'|'dccp'}
```

46.2. Viewing the current status and settings of `firewalld`

To monitor the firewalld service, you can display the status, allowed services, and settings.

46.2.1. Viewing the current status of `firewalld`

The firewall service, firewalld, is installed on the system by default. Use the firewalld CLI interface to check that the service is running.

Procedure

To see the status of the service:
```
# firewall-cmd --state
```

For more information about the service status, use the systemctl status sub-command:

# systemctl status firewalld
firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor pr
   Active: active (running) since Mon 2017-12-18 16:05:15 CET; 50min ago
     Docs: man:firewalld(1)
 Main PID: 705 (firewalld)
    Tasks: 2 (limit: 4915)
   CGroup: /system.slice/firewalld.service
           └─705 /usr/bin/python3 -Es /usr/sbin/firewalld --nofork --nopid

46.2.2. Viewing allowed services using GUI

To view the list of services using the graphical firewall-config tool, press the Super key to enter the Activities Overview, type firewall, and press Enter. The firewall-config tool appears. You can now view the list of services under the Services tab.

You can start the graphical firewall configuration tool using the command-line.

Prerequisites

You installed the firewall-config package.

Procedure

To start the graphical firewall configuration tool using the command-line:
```
$ firewall-config
```

The Firewall Configuration window opens. Note that this command can be run as a normal user, but you are prompted for an administrator password occasionally.

46.2.3. Viewing firewalld settings using CLI

With the CLI client, it is possible to get different views of the current firewall settings. The --list-all option shows a complete overview of the firewalld settings.

firewalld uses zones to manage the traffic. If a zone is not specified by the --zone option, the command is effective in the default zone assigned to the active network interface and connection.

Procedure

To list all the relevant information for the default zone:

# firewall-cmd --list-all
public
  target: default
  icmp-block-inversion: no
  interfaces:
  sources:
  services: ssh dhcpv6-client
  ports:
  protocols:
  masquerade: no
  forward-ports:
  source-ports:
  icmp-blocks:
  rich rules:

To specify the zone for which to display the settings, add the --zone=zone-name argument to the firewall-cmd --list-all command, for example:

# firewall-cmd --list-all --zone=home
home
  target: default
  icmp-block-inversion: no
  interfaces:
  sources:
  services: ssh mdns samba-client dhcpv6-client
... [trimmed for clarity]

To see the settings for particular information, such as services or ports, use a specific option. See the firewalld manual pages or get a list of the options using the command help:
```
# firewall-cmd --help
```
To see which services are allowed in the current zone:
```
# firewall-cmd --list-services
ssh dhcpv6-client
```

Note

Listing the settings for a certain subpart using the CLI tool can sometimes be difficult to interpret. For example, you allow the SSH service and firewalld opens the necessary port (22) for the service. Later, if you list the allowed services, the list shows the SSH service, but if you list open ports, it does not show any. Therefore, it is recommended to use the --list-all option to make sure you receive a complete information.

46.3. Controlling network traffic using `firewalld`

The firewalld package installs a large number of predefined service files and you can add more or customize them. You can then use these service definitions to open or close ports for services without knowing the protocol and port numbers they use.

46.3.1. Disabling all traffic in case of emergency using CLI

In an emergency situation, such as a system attack, it is possible to disable all network traffic and cut off the attacker.

Procedure

To immediately disable networking traffic, switch panic mode on:
```
# firewall-cmd --panic-on
```
Important

Enabling panic mode stops all networking traffic. For this reason, it should be used only when you have the physical access to the machine or if you are logged in using a serial console.
Switching off panic mode reverts the firewall to its permanent settings. To switch panic mode off, enter:
```
# firewall-cmd --panic-off
```

Verification

To see whether panic mode is switched on or off, use:
```
# firewall-cmd --query-panic
```

46.3.2. Controlling traffic with predefined services using CLI

The most straightforward method to control traffic is to add a predefined service to firewalld. This opens all necessary ports and modifies other settings according to the service definition file.

Procedure

Check that the service is not already allowed:

# firewall-cmd --list-services
ssh dhcpv6-client

List all predefined services:

# firewall-cmd --get-services
RH-Satellite-6 amanda-client amanda-k5-client bacula bacula-client bitcoin bitcoin-rpc bitcoin-testnet bitcoin-testnet-rpc ceph ceph-mon cfengine condor-collector ctdb dhcp dhcpv6 dhcpv6-client dns docker-registry ...
[trimmed for clarity]

Add the service to the allowed services:

# firewall-cmd --add-service=<service-name>

Make the new settings persistent:
```
# firewall-cmd --runtime-to-permanent
```

46.3.3. Controlling traffic with predefined services using GUI

You can control the network traffic with predefined services using graphical user interface.

Prerequisites

You installed the firewall-config package

Procedure

To enable or disable a predefined or custom service:
1. Start the
  
  firewall-config
  
  tool and select the network zone whose services are to be configured.
2. Select the Zones tab and then the Services tab below.
3. Select the check box for each type of service you want to trust or clear the check box to block a service in the selected zone.
To edit a service:
1. Start the
  
  firewall-config
  
  tool.
2. Select Permanent from the menu labeled Configuration. Additional icons and menu buttons appear at the bottom of the
  
  Services
  
  window.
3. Select the service you want to configure.

The Ports, Protocols, and Source Port tabs enable adding, changing, and removing of ports, protocols, and source port for the selected service. The modules tab is for configuring Netfilter helper modules. The Destination tab enables limiting traffic to a particular destination address and Internet Protocol (IPv4 or IPv6).

Note

It is not possible to alter service settings in the Runtime mode.

46.3.4. Adding new services

Services can be added and removed using the graphical firewall-config tool, firewall-cmd, and firewall-offline-cmd. Alternatively, you can edit the XML files in /etc/firewalld/services/. If a service is not added or changed by the user, then no corresponding XML file are found in /etc/firewalld/services/. The files /usr/lib/firewalld/services/ can be used as templates if you want to add or change a service.

Note

Service names must be alphanumeric and can, additionally, include only _ (underscore) and - (dash) characters.

Procedure

To add a new service in a terminal, use firewall-cmd, or firewall-offline-cmd in case of not active firewalld.

Enter the following command to add a new and empty service:
```
$ firewall-cmd --new-service=service-name
 --permanent
```
To add a new service using a local file, use the following command:
```
$ firewall-cmd --new-service-from-file=service-name
.xml --permanent
```
You can change the service name with the additional --name=service-name option.
As soon as service settings are changed, an updated copy of the service is placed into /etc/firewalld/services/.

As root, you can enter the following command to copy a service manually:
```
# cp /usr/lib/firewalld/services/service-name.xml /etc/firewalld/services/service-name.xml
```

firewalld loads files from /usr/lib/firewalld/services in the first place. If files are placed in /etc/firewalld/services and they are valid, then these will override the matching files from /usr/lib/firewalld/services. The overridden files in /usr/lib/firewalld/services are used as soon as the matching files in /etc/firewalld/services have been removed or if firewalld has been asked to load the defaults of the services. This applies to the permanent environment only. A reload is needed to get these fallbacks also in the runtime environment.

46.3.5. Opening ports using GUI

To permit traffic through the firewall to a certain port, you can open the port in the GUI.

Prerequisites

You installed the firewall-config package

Procedure

Start the

firewall-config

tool and select the network zone whose settings you want to change.
Select the Ports tab and click the

Add

button on the right-hand side. The Port and Protocol window opens.
Enter the port number or range of ports to permit.
Select tcp or udp from the list.

46.3.6. Controlling traffic with protocols using GUI

To permit traffic through the firewall using a certain protocol, you can use the GUI.

Prerequisites

You installed the firewall-config package

Procedure

Start the

firewall-config

tool and select the network zone whose settings you want to change.
Select the Protocols tab and click the Add button on the right-hand side. The Protocol window opens.
Either select a protocol from the list or select the Other Protocol check box and enter the protocol in the field.

46.3.7. Opening source ports using GUI

To permit traffic through the firewall from a certain port, you can use the GUI.

Prerequisites

You installed the firewall-config package

Procedure

Start the firewall-config tool and select the network zone whose settings you want to change.
Select the Source Port tab and click the Add button on the right-hand side. The Source Port window opens.
Enter the port number or range of ports to permit. Select tcp or udp from the list.

46.4. Controlling ports using CLI

Ports are logical devices that enable an operating system to receive and distinguish network traffic and forward it accordingly to system services. These are usually represented by a daemon that listens on the port, that is it waits for any traffic coming to this port.

Normally, system services listen on standard ports that are reserved for them. The httpd daemon, for example, listens on port 80. However, system administrators by default configure daemons to listen on different ports to enhance security or for other reasons.

46.4.1. Opening a port

Through open ports, the system is accessible from the outside, which represents a security risk. Generally, keep ports closed and only open them if they are required for certain services.

Procedure

To get a list of open ports in the current zone:

List all allowed ports:
```
# firewall-cmd --list-ports
```
Add a port to the allowed ports to open it for incoming traffic:
```
# firewall-cmd --add-port=port-number
/port-type
```
The port types are either tcp, udp, sctp, or dccp. The type must match the type of network communication.
Make the new settings persistent:
```
# firewall-cmd --runtime-to-permanent
```
The port types are either tcp, udp, sctp, or dccp. The type must match the type of network communication.

46.4.2. Closing a port

When an open port is no longer needed, close that port in firewalld. It is highly recommended to close all unnecessary ports as soon as they are not used because leaving a port open represents a security risk.

Procedure

To close a port, remove it from the list of allowed ports:

List all allowed ports:
```
# firewall-cmd --list-ports
```
Warning

This command will only give you a list of ports that have been opened as ports. You will not be able to see any open ports that have been opened as a service. Therefore, you should consider using the --list-all option instead of --list-ports.
Remove the port from the allowed ports to close it for the incoming traffic:
```
# firewall-cmd --remove-port=port-number/port-type
```
Make the new settings persistent:
```
# firewall-cmd --runtime-to-permanent
```

46.5. Working with firewalld zones

Zones represent a concept to manage incoming traffic more transparently. The zones are connected to networking interfaces or assigned a range of source addresses. You manage firewall rules for each zone independently, which enables you to define complex firewall settings and apply them to the traffic.

46.5.1. Listing zones

You can list zones using the command line.

Procedure

To see which zones are available on your system:
```
# firewall-cmd --get-zones
```
The firewall-cmd --get-zones command displays all zones that are available on the system, but it does not show any details for particular zones.
To see detailed information for all zones:
```
# firewall-cmd --list-all-zones
```
To see detailed information for a specific zone:
```
# firewall-cmd --zone=zone-name --list-all
```

46.5.2. Modifying firewalld settings for a certain zone

The Controlling traffic with predefined services using cli and Controlling ports using cli explain how to add services or modify ports in the scope of the current working zone. Sometimes, it is required to set up rules in a different zone.

Procedure

To work in a different zone, use the --zone=zone-name option. For example, to allow the SSH service in the zone public:
```
# firewall-cmd --add-service=ssh --zone=public
```

46.5.3. Changing the default zone

System administrators assign a zone to a networking interface in its configuration files. If an interface is not assigned to a specific zone, it is assigned to the default zone. After each restart of the firewalld service, firewalld loads the settings for the default zone and makes it active.

Procedure

To set up the default zone:

Display the current default zone:
```
# firewall-cmd --get-default-zone
```
Set the new default zone:
```
# firewall-cmd --set-default-zone zone-name
```
Note

Following this procedure, the setting is a permanent setting, even without the --permanent option.

46.5.4. Assigning a network interface to a zone

It is possible to define different sets of rules for different zones and then change the settings quickly by changing the zone for the interface that is being used. With multiple interfaces, a specific zone can be set for each of them to distinguish traffic that is coming through them.

Procedure

To assign the zone to a specific interface:

List the active zones and the interfaces assigned to them:
```
# firewall-cmd --get-active-zones
```

Assign the interface to a different zone:

# firewall-cmd --zone=zone_name
 --change-interface=interface_name
 --permanent

46.5.5. Assigning a zone to a connection using nmcli

You can add a firewalld zone to a NetworkManager connection using the nmcli utility.

Procedure

Assign the zone to the NetworkManager connection profile:

# nmcli connection modify

profile

connection.zone

zone_name

Activate the connection:
```
# nmcli connection up profile
```

46.5.6. Manually assigning a zone to a network connection in an ifcfg file

When the connection is managed by NetworkManager, it must be aware of a zone that it uses. For every network connection, a zone can be specified, which provides the flexibility of various firewall settings according to the location of the computer with portable devices. Thus, zones and settings can be specified for different locations, such as company or home.

Procedure

To set a zone for a connection, edit the /etc/sysconfig/network-scripts/ifcfg-connection_name file and add a line that assigns a zone to this connection:
```
ZONE=zone_name
```

46.5.7. Creating a new zone

To use custom zones, create a new zone and use it just like a predefined zone. New zones require the --permanent option, otherwise the command does not work.

Procedure

Create a new zone:

firewall-cmd --permanent --new-zone=

zone-name

Check if the new zone is added to your permanent settings:
```
# firewall-cmd --get-zones
```
Make the new settings persistent:
```
# firewall-cmd --runtime-to-permanent
```

46.5.8. Zone configuration files

Zones can also be created using a zone configuration file. This approach can be helpful when you need to create a new zone, but want to reuse the settings from a different zone and only alter them a little.

A firewalld zone configuration file contains the information for a zone. These are the zone description, services, ports, protocols, icmp-blocks, masquerade, forward-ports and rich language rules in an XML file format. The file name has to be zone-name.xml where the length of zone-name is currently limited to 17 chars. The zone configuration files are located in the /usr/lib/firewalld/zones/ and /etc/firewalld/zones/ directories.

The following example shows a configuration that allows one service (SSH) and one port range, for both the TCP and UDP protocols:

<?xml version="1.0" encoding="utf-8"?>
<zone>
  <short>My Zone</short>
  <description>Here you can describe the characteristic features of the zone.</description>
  <service name="ssh"/>
  <port protocol="udp" port="1025-65535"/>
  <port protocol="tcp" port="1025-65535"/>
</zone>

To change settings for that zone, add or remove sections to add ports, forward ports, services, and so on.

Additional resources

firewalld.zone manual page

46.5.9. Using zone targets to set default behavior for incoming traffic

For every zone, you can set a default behavior that handles incoming traffic that is not further specified. Such behavior is defined by setting the target of the zone. There are four options:

ACCEPT: Accepts all incoming packets except those disallowed by specific rules.
REJECT: Rejects all incoming packets except those allowed by specific rules. When firewalld rejects packets, the source machine is informed about the rejection.
DROP: Drops all incoming packets except those allowed by specific rules. When firewalld drops packets, the source machine is not informed about the packet drop.
default: Similar behavior as for REJECT, but with special meanings in certain scenarios. For details, see the Options to Adapt and Query Zones and Policies section in the firewall-cmd(1) man page.

Procedure

To set a target for a zone:

List the information for the specific zone to see the default target:
```
# firewall-cmd --zone=zone-name
 --list-all
```

Set a new target in the zone:

# firewall-cmd --permanent --zone=zone-name --set-target=<default|ACCEPT|REJECT|DROP>

Additional resources

firewall-cmd(1) man page

46.6. Using zones to manage incoming traffic depending on a source

You can use zones to manage incoming traffic based on its source. That enables you to sort incoming traffic and route it through different zones to allow or disallow services that can be reached by that traffic.

If you add a source to a zone, the zone becomes active and any incoming traffic from that source will be directed through it. You can specify different settings for each zone, which is applied to the traffic from the given sources accordingly. You can use more zones even if you only have one network interface.

46.6.1. Adding a source

To route incoming traffic into a specific zone, add the source to that zone. The source can be an IP address or an IP mask in the classless inter-domain routing (CIDR) notation.

Note

In case you add multiple zones with an overlapping network range, they are ordered alphanumerically by zone name and only the first one is considered.

To set the source in the current zone:
```
# firewall-cmd --add-source=<source>
```

To set the source IP address for a specific zone:

# firewall-cmd --zone=zone-name --add-source=<source>

The following procedure allows all incoming traffic from 192.168.2.15 in the trusted zone:

Procedure

List all available zones:
```
# firewall-cmd --get-zones
```
Add the source IP to the trusted zone in the permanent mode:
```
# firewall-cmd --zone=trusted --add-source=192.168.2.15
```
Make the new settings persistent:
```
# firewall-cmd --runtime-to-permanent
```

46.6.2. Removing a source

Removing a source from the zone cuts off the traffic coming from it.

Procedure

List allowed sources for the required zone:

# firewall-cmd --zone=zone-name --list-sources

Remove the source from the zone permanently:

# firewall-cmd --zone=zone-name --remove-source=<source>

Make the new settings persistent:
```
# firewall-cmd --runtime-to-permanent
```

46.6.3. Adding a source port

To enable sorting the traffic based on a port of origin, specify a source port using the --add-source-port option. You can also combine this with the --add-source option to limit the traffic to a certain IP address or IP range.

Procedure

To add a source port:

# firewall-cmd --zone=zone-name --add-source-port=<port-name>/<tcp|udp|sctp|dccp>

46.6.4. Removing a source port

By removing a source port you disable sorting the traffic based on a port of origin.

Procedure

To remove a source port:

# firewall-cmd --zone=zone-name --remove-source-port=<port-name>/<tcp|udp|sctp|dccp>

46.6.5. Using zones and sources to allow a service for only a specific domain

To allow traffic from a specific network to use a service on a machine, use zones and source. The following procedure allows only HTTP traffic from the 192.0.2.0/24 network while any other traffic is blocked.

Warning

When you configure this scenario, use a zone that has the default target. Using a zone that has the target set to ACCEPT is a security risk, because for traffic from 192.0.2.0/24, all network connections would be accepted.

Procedure

List all available zones:

# firewall-cmd --get-zones
block dmz drop external home internal public trusted work

Add the IP range to the internal zone to route the traffic originating from the source through the zone:
```
# firewall-cmd --zone=internal --add-source=192.0.2.0/24
```

Add the http service to the internal zone:

# firewall-cmd --zone=internal --add-service=http

Make the new settings persistent:
```
# firewall-cmd --runtime-to-permanent
```

Verification

Check that the internal zone is active and that the service is allowed in it:

# firewall-cmd --zone=internal --list-all internal (active) target: default icmp-block-inversion: no interfaces: sources:

192.0.2.0/24

services: cockpit dhcpv6-client mdns samba-client ssh

http

...

Additional resources

firewalld.zones(5) man page

46.7. Filtering forwarded traffic between zones

With a policy object, users can group different identities that require similar permissions in the policy. You can apply policies depending on the direction of the traffic.

The policy objects feature provides forward and output filtering in firewalld. You can use firewalld to filter traffic between different zones to allow access to locally hosted VMs to connect the host.

46.7.1. The relationship between policy objects and zones

Policy objects allow the user to attach firewalld’s primitives’ such as services, ports, and rich rules to the policy. You can apply the policy objects to traffic that passes between zones in a stateful and unidirectional manner.

# firewall-cmd --permanent --new-policy

myOutputPolicy

# firewall-cmd --permanent --policy

myOutputPolicy

--add-ingress-zone HOST # firewall-cmd --permanent --policy

myOutputPolicy

--add-egress-zone ANY

HOST and ANY are the symbolic zones used in the ingress and egress zone lists.

The HOST symbolic zone allows policies for the traffic originating from or has a destination to the host running firewalld.
The ANY symbolic zone applies policy to all the current and future zones. ANY symbolic zone acts as a wildcard for all zones.

46.7.2. Using priorities to sort policies

Multiple policies can apply to the same set of traffic, therefore, priorities should be used to create an order of precedence for the policies that may be applied.

To set a priority to sort the policies:

# firewall-cmd --permanent --policy

mypolicy

--set-priority

-500

In the above example -500 is a lower priority value but has higher precedence. Thus, -500 will execute before -100. Higher priority values have precedence over lower values.

The following rules apply to policy priorities:

Policies with negative priorities apply before rules in zones.
Policies with positive priorities apply after rules in zones.
Priority 0 is reserved and hence is unusable.

46.7.3. Using policy objects to filter traffic between locally hosted Containers and a network physically connected to the host

The policy objects feature allows users to filter their container and virtual machine traffic.

Procedure

Create a new policy.

# firewall-cmd --permanent --new-policy podmanToHost

Block all traffic.

# firewall-cmd --permanent --policy podmanToHost --set-target REJECT

# firewall-cmd --permanent --policy podmanToHost --add-service dhcp

# firewall-cmd --permanent --policy podmanToHost --add-service dns

Note

Red Hat recommends that you block all traffic to the host by default and then selectively open the services you need for the host.

Define the ingress zone to use with the policy.

# firewall-cmd --permanent --policy podmanToHost --add-ingress-zone podman

Define the egress zone to use with the policy.

# firewall-cmd --permanent --policy podmanToHost --add-egress-zone ANY

Verification

Verify information about the policy.

# firewall-cmd --info-policy podmanToHost

46.7.4. Setting the default target of policy objects

You can specify –set-target options for policies. The following targets are available:

ACCEPT

– accepts the packet
DROP

– drops the unwanted packets
REJECT

– rejects unwanted packets with an ICMP reply
CONTINUE (default) – packets will be subject to rules in following policies and zones.
```
# firewall-cmd --permanent --policy mypolicy
 --set-target CONTINUE
```

Verification

Verify information about the policy
```
# firewall-cmd --info-policy mypolicy
```

46.8. Configuring NAT using firewalld

With firewalld, you can configure the following network address translation (NAT) types:

Masquerading
Source NAT (SNAT)
Destination NAT (DNAT)
Redirect

46.8.1. NAT types

These are the different network address translation (NAT) types:

Masquerading and source NAT (SNAT)

Use one of these NAT types to change the source IP address of packets. For example, Internet Service Providers do not route private IP ranges, such as 10.0.0.0/8. If you use private IP ranges in your network and users should be able to reach servers on the Internet, map the source IP address of packets from these ranges to a public IP address.

Masquerading and SNAT are very similar to one another. The differences are:

Masquerading automatically uses the IP address of the outgoing interface. Therefore, use masquerading if the outgoing interface uses a dynamic IP address.
SNAT sets the source IP address of packets to a specified IP and does not dynamically look up the IP of the outgoing interface. Therefore, SNAT is faster than masquerading. Use SNAT if the outgoing interface uses a fixed IP address.

Destination NAT (DNAT)

Use this NAT type to rewrite the destination address and port of incoming packets. For example, if your web server uses an IP address from a private IP range and is, therefore, not directly accessible from the Internet, you can set a DNAT rule on the router to redirect incoming traffic to this server.

Redirect

This type is a special case of DNAT that redirects packets to the local machine depending on the chain hook. For example, if a service runs on a different port than its standard port, you can redirect incoming traffic from the standard port to this specific port.

46.8.2. Configuring IP address masquerading

You can enable IP masquerading on your system. IP masquerading hides individual machines behind a gateway when accessing the Internet.

Procedure

To check if IP masquerading is enabled (for example, for the external zone), enter the following command as root:
```
# firewall-cmd --zone=
external
 --query-masquerade
```
The command prints yes with exit status 0 if enabled. It prints no with exit status 1 otherwise. If zone is omitted, the default zone will be used.
To enable IP masquerading, enter the following command as root:
```
# firewall-cmd --zone=
external
 --add-masquerade
```
To make this setting persistent, pass the --permanent option to the command.
To disable IP masquerading, enter the following command as root:
```
# firewall-cmd --zone=
external
 --remove-masquerade
```
To make this setting permanent, pass the --permanent option to the command.

46.9. Using DNAT to forward HTTPS traffic to a different host

If your web server runs in a DMZ with private IP addresses, you can configure destination network address translation (DNAT) to enable clients on the internet to connect to this web server. In this case, the host name of the web server resolves to the public IP address of the router. When a client establishes a connection to a defined port on the router, the router forwards the packets to the internal web server.

Prerequisites

The DNS server resolves the host name of the web server to the router’s IP address.
You know the following settings:
- The private IP address and port number that you want to forward
- The IP protocol to be used
- The destination IP address and port of the web server where you want to redirect the packets

Procedure

Create a firewall policy:
```
# firewall-cmd --permanent --new-policy 
ExamplePolicy
```
The policies, as opposed to zones, allow packet filtering for input, output, and forwarded traffic. This is important, because forwarding traffic to endpoints on locally run web servers, containers, or virtual machines requires such capability.
Configure symbolic zones for the ingress and egress traffic to also enable the router itself to connect to its local IP address and forward this traffic:
```
# firewall-cmd --permanent --policy=
ExamplePolicy
 --add-ingress-zone=HOST
# firewall-cmd --permanent --policy=
ExamplePolicy
 --add-egress-zone=ANY
```
The --add-ingress-zone=HOST option refers to packets generated locally, which are transmitted out of the local host. The --add-egress-zone=ANY option refers to traffic destined to any zone.
Add a rich rule that forwards traffic to the web server:
```
# firewall-cmd --permanent --policy=
ExamplePolicy
 --add-rich-rule='rule family="ipv4" destination address="192.0.2.1
" forward-port port="443
" protocol="tcp" to-port="443
" to-addr="192.51.100.20
"'
```
The rich rule forwards TCP traffic from port 443 on the router’s IP address 192.0.2.1 to port 443 of the web server’s IP 192.51.100.20. The rule uses the ExamplePolicy to ensure that the router can also connect to its local IP address.
Reload the firewall configuration files:
```
# firewall-cmd --reload
success
```

Activate routing of 127.0.0.0/8 in the kernel:

echo "net.ipv4.conf.all.route_localnet=1" > /etc/sysctl.d/90-enable-route-localnet.conf

sysctl -p /etc/sysctl.d/90-enable-route-localnet.conf

Verification

Connect to the router’s IP address and port that you have forwarded to the web server:
```
# curl https://192.0.2.1:443
```

Optional: Verify that net.ipv4.conf.all.route_localnet is active:

sysctl net.ipv4.conf.all.route_localnet

net.ipv4.conf.all.route_localnet = 1

Verify that ExamplePolicy is active and contains the settings you need. Especially the source IP address and port, protocol to be used, and the destination IP address and port:

firewall-cmd --info-policy=

ExamplePolicy

ExamplePolicy (active) priority: -1 target: CONTINUE ingress-zones: HOST egress-zones: ANY services: ports: protocols: masquerade: no forward-ports: source-ports: icmp-blocks: rich rules: rule family="ipv4" destination address="192.0.2.1" forward-port port="443" protocol="tcp" to-port="443" to-addr="192.51.100.20"

Additional resources

firewall-cmd(1), firewalld.policies(5), firewalld.richlanguage(5), sysctl(8), and sysctl.conf(5) man pages
Using configuration files in /etc/sysctl.d/ to adjust kernel parameters

46.10. Managing ICMP requests

The Internet Control Message Protocol (ICMP) is a supporting protocol that is used by various network devices to send error messages and operational information indicating a connection problem, for example, that a requested service is not available. ICMP differs from transport protocols such as TCP and UDP because it is not used to exchange data between systems.

Unfortunately, it is possible to use the ICMP messages, especially echo-request and echo-reply, to reveal information about your network and misuse such information for various kinds of fraudulent activities. Therefore, firewalld enables blocking the ICMP requests to protect your network information.

46.10.1. Listing and blocking ICMP requests

Listing ICMP requests

The ICMP requests are described in individual XML files that are located in the /usr/lib/firewalld/icmptypes/ directory. You can read these files to see a description of the request. The firewall-cmd command controls the ICMP requests manipulation.

To list all available ICMP types:
```
# firewall-cmd --get-icmptypes
```
The ICMP request can be used by IPv4, IPv6, or by both protocols. To see for which protocol the ICMP request has used:
```
# firewall-cmd --info-icmptype=<icmptype>
```
The status of an ICMP request shows yes if the request is currently blocked or no if it is not. To see if an ICMP request is currently blocked:
```
# firewall-cmd --query-icmp-block=<icmptype>
```

Blocking or unblocking ICMP requests

When your server blocks ICMP requests, it does not provide the information that it normally would. However, that does not mean that no information is given at all. The clients receive information that the particular ICMP request is being blocked (rejected). Blocking the ICMP requests should be considered carefully, because it can cause communication problems, especially with IPv6 traffic.

To see if an ICMP request is currently blocked:
```
# firewall-cmd --query-icmp-block=<icmptype>
```

To block an ICMP request:

# firewall-cmd --add-icmp-block=<icmptype>

To remove the block for an ICMP request:

# firewall-cmd --remove-icmp-block=<icmptype>

Blocking ICMP requests without providing any information at all

Normally, if you block ICMP requests, clients know that you are blocking it. So, a potential attacker who is sniffing for live IP addresses is still able to see that your IP address is online. To hide this information completely, you have to drop all ICMP requests.

To block and drop all ICMP requests:

Set the target of your zone to DROP:

# firewall-cmd --permanent --set-target=DROP

Now, all traffic, including ICMP requests, is dropped, except traffic which you have explicitly allowed.

To block and drop certain ICMP requests and allow others:

Set the target of your zone to DROP:

# firewall-cmd --permanent --set-target=DROP

Add the ICMP block inversion to block all ICMP requests at once:
```
# firewall-cmd --add-icmp-block-inversion
```
Add the ICMP block for those ICMP requests that you want to allow:
```
# firewall-cmd --add-icmp-block=<icmptype>
```
Make the new settings persistent:
```
# firewall-cmd --runtime-to-permanent
```

The block inversion inverts the setting of the ICMP requests blocks, so all requests, that were not previously blocked, are blocked because of the target of your zone changes to DROP. The requests that were blocked are not blocked. This means that if you want to unblock a request, you must use the blocking command.

To revert the block inversion to a fully permissive setting:

Set the target of your zone to default or ACCEPT:

# firewall-cmd --permanent --set-target=default

Remove all added blocks for ICMP requests:

# firewall-cmd --remove-icmp-block=<icmptype>

Remove the ICMP block inversion:

# firewall-cmd --remove-icmp-block-inversion

Make the new settings persistent:
```
# firewall-cmd --runtime-to-permanent
```

46.10.2. Configuring the ICMP filter using GUI

To enable or disable an ICMP filter, start the

firewall-config

tool and select the network zone whose messages are to be filtered. Select the ICMP Filter tab and select the check box for each type of ICMP message you want to filter. Clear the check box to disable a filter. This setting is per direction and the default allows everything.
To enable inverting the ICMP Filter, click the Invert Filter check box on the right. Only marked ICMP types are now accepted, all other are rejected. In a zone using the DROP target, they are dropped.

46.11. Setting and controlling IP sets using `firewalld`

To see the list of IP set types supported by firewalld, enter the following command as root.

~]# firewall-cmd --get-ipset-types
hash:ip hash:ip,mark hash:ip,port hash:ip,port,ip hash:ip,port,net hash:mac hash:net hash:net,iface hash:net,net hash:net,port hash:net,port,net

46.11.1. Configuring IP set options using CLI

IP sets can be used in firewalld zones as sources and also as sources in rich rules. In Red Hat Enterprise Linux, the preferred method is to use the IP sets created with firewalld in a direct rule.

To list the IP sets known to firewalld in the permanent environment, use the following command as root:
```
# firewall-cmd --permanent --get-ipsets
```
To add a new IP set, use the following command using the permanent environment as root:
```
# firewall-cmd --permanent --new-ipset=test --type=hash:net
success
```
The previous command creates a new IP set with the name test and the hash:net type for IPv4. To create an IP set for use with IPv6, add the --option=family=inet6 option. To make the new setting effective in the runtime environment, reload firewalld.
List the new IP set with the following command as root:
```
# firewall-cmd --permanent --get-ipsets
test
```
To get more information about the IP set, use the following command as root:
```
# firewall-cmd --permanent --info-ipset=test
test
type: hash:net
options:
entries:
```
Note that the IP set does not have any entries at the moment.
To add an entry to the test IP set, use the following command as root:
```
# firewall-cmd --permanent --ipset=test
 --add-entry=192.168.0.1
success
```
The previous command adds the IP address 192.168.0.1 to the IP set.
To get the list of current entries in the IP set, use the following command as root:
```
# firewall-cmd --permanent --ipset=test --get-entries
192.168.0.1
```
Generate a file containing a list of IP addresses, for example:
```
# cat > iplist.txt <<EOL
192.168.0.2
192.168.0.3
192.168.1.0/24
192.168.2.254
EOL
```
The file with the list of IP addresses for an IP set should contain an entry per line. Lines starting with a hash, a semi-colon, or empty lines are ignored.

To add the addresses from the iplist.txt file, use the following command as root:

# firewall-cmd --permanent --ipset=

test

--add-entries-from-file=

iplist.txt

success

To see the extended entries list of the IP set, use the following command as root:

# firewall-cmd --permanent --ipset=

test

--get-entries 192.168.0.1 192.168.0.2 192.168.0.3 192.168.1.0/24 192.168.2.254

To remove the addresses from the IP set and to check the updated entries list, use the following commands as root:

# firewall-cmd --permanent --ipset=

test

--remove-entries-from-file=

iplist.txt

success # firewall-cmd --permanent --ipset=test --get-entries 192.168.0.1

You can add the IP set as a source to a zone to handle all traffic coming in from any of the addresses listed in the IP set with a zone. For example, to add the test IP set as a source to the drop zone to drop all packets coming from all entries listed in the test IP set, use the following command as root:
```
# firewall-cmd --permanent --zone=drop --add-source=ipset:test
success
```
The ipset: prefix in the source shows firewalld that the source is an IP set and not an IP address or an address range.

Only the creation and removal of IP sets is limited to the permanent environment, all other IP set options can be used also in the runtime environment without the --permanent option.

Warning

Red Hat does not recommend using IP sets that are not managed through firewalld. To use such IP sets, a permanent direct rule is required to reference the set, and a custom service must be added to create these IP sets. This service needs to be started before firewalld starts, otherwise firewalld is not able to add the direct rules using these sets. You can add permanent direct rules with the /etc/firewalld/direct.xml file.

46.12. Prioritizing rich rules

By default, rich rules are organized based on their rule action. For example, deny rules have precedence over allow rules. The priority parameter in rich rules provides administrators fine-grained control over rich rules and their execution order.

46.12.1. How the priority parameter organizes rules into different chains

You can set the priority parameter in a rich rule to any number between -32768 and 32767, and lower values have higher precedence.

The firewalld service organizes rules based on their priority value into different chains:

Priority lower than 0: the rule is redirected into a chain with the _pre suffix.
Priority higher than 0: the rule is redirected into a chain with the _post suffix.
Priority equals 0: based on the action, the rule is redirected into a chain with the _log, _deny, or _allow the action.

Inside these sub-chains, firewalld sorts the rules based on their priority value.

46.12.2. Setting the priority of a rich rule

The following is an example of how to create a rich rule that uses the priority parameter to log all traffic that is not allowed or denied by other rules. You can use this rule to flag unexpected traffic.

Procedure

Add a rich rule with a very low precedence to log all traffic that has not been matched by other rules:
```
# firewall-cmd --add-rich-rule='rule priority=32767 log prefix="UNEXPECTED: " limit value="5/m"'
```
The command additionally limits the number of log entries to 5 per minute.

Optionally, display the nftables rule that the command in the previous step created:

# nft list chain inet firewalld filter_IN_public_post
table inet firewalld {
  chain filter_IN_public_post {
    log prefix "UNEXPECTED: " limit rate 5/minute
  }
}

46.13. Configuring firewall lockdown

Local applications or services are able to change the firewall configuration if they are running as root (for example, libvirt). With this feature, the administrator can lock the firewall configuration so that either no applications or only applications that are added to the lockdown allow list are able to request firewall changes. The lockdown settings default to disabled. If enabled, the user can be sure that there are no unwanted configuration changes made to the firewall by local applications or services.

46.13.1. Configuring lockdown using CLI

You can enable or disable the lockdown feature using the command line.

Procedure

To query whether lockdown is enabled, use the following command as root:
```
# firewall-cmd --query-lockdown
```
The command prints yes with exit status 0 if lockdown is enabled. It prints no with exit status 1 otherwise.
To enable lockdown, enter the following command as root:
```
# firewall-cmd --lockdown-on
```
To disable lockdown, use the following command as root:
```
# firewall-cmd --lockdown-off
```

46.13.2. Configuring lockdown allowlist options using CLI

The lockdown allowlist can contain commands, security contexts, users and user IDs. If a command entry on the allowlist ends with an asterisk “*”, then all command lines starting with that command will match. If the “*” is not there then the absolute command including arguments must match.

The context is the security (SELinux) context of a running application or service. To get the context of a running application use the following command:
```
$ ps -e --context
```
That command returns all running applications. Pipe the output through the grep tool to get the application of interest. For example:
```
$ ps -e --context | grep example_program
```
To list all command lines that are in the allowlist, enter the following command as root:
```
# firewall-cmd --list-lockdown-whitelist-commands
```

To add a command command to the allowlist, enter the following command as root:

# firewall-cmd --add-lockdown-whitelist-command='/usr/bin/python3 -Es /usr/bin/command'

To remove a command command from the allowlist, enter the following command as root:

# firewall-cmd --remove-lockdown-whitelist-command='/usr/bin/python3 -Es /usr/bin/command'

To query whether the command command is in the allowlist, enter the following command as root:
```
# firewall-cmd --query-lockdown-whitelist-command='/usr/bin/python3 -Es /usr/bin/command'
```
The command prints yes with exit status 0 if true. It prints no with exit status 1 otherwise.
To list all security contexts that are in the allowlist, enter the following command as root:
```
# firewall-cmd --list-lockdown-whitelist-contexts
```
To add a context context to the allowlist, enter the following command as root:
```
# firewall-cmd --add-lockdown-whitelist-context=context
```
To remove a context context from the allowlist, enter the following command as root:
```
# firewall-cmd --remove-lockdown-whitelist-context=context
```
To query whether the context context is in the allowlist, enter the following command as root:
```
# firewall-cmd --query-lockdown-whitelist-context=context
```
Prints yes with exit status 0, if true, prints no with exit status 1 otherwise.
To list all user IDs that are in the allowlist, enter the following command as root:
```
# firewall-cmd --list-lockdown-whitelist-uids
```
To add a user ID uid to the allowlist, enter the following command as root:
```
# firewall-cmd --add-lockdown-whitelist-uid=uid
```
To remove a user ID uid from the allowlist, enter the following command as root:
```
# firewall-cmd --remove-lockdown-whitelist-uid=uid
```
To query whether the user ID uid is in the allowlist, enter the following command:
```
$ firewall-cmd --query-lockdown-whitelist-uid=uid
```
Prints yes with exit status 0, if true, prints no with exit status 1 otherwise.
To list all user names that are in the allowlist, enter the following command as root:
```
# firewall-cmd --list-lockdown-whitelist-users
```
To add a user name user to the allowlist, enter the following command as root:
```
# firewall-cmd --add-lockdown-whitelist-user=user
```
To remove a user name user from the allowlist, enter the following command as root:
```
# firewall-cmd --remove-lockdown-whitelist-user=user
```
To query whether the user name user is in the allowlist, enter the following command:
```
$ firewall-cmd --query-lockdown-whitelist-user=user
```
Prints yes with exit status 0, if true, prints no with exit status 1 otherwise.

46.13.3. Configuring lockdown allowlist options using configuration files

The default allowlist configuration file contains the NetworkManager context and the default context of libvirt. The user ID 0 is also on the list.

+ The allowlist configuration files are stored in the /etc/firewalld/ directory.

<?xml version="1.0" encoding="utf-8"?>
	<whitelist>
	  <selinux context="system_u:system_r:NetworkManager_t:s0"/>
	  <selinux context="system_u:system_r:virtd_t:s0-s0:c0.c1023"/>
	  <user id="0"/>
	</whitelist>

Following is an example allowlist configuration file enabling all commands for the firewall-cmd utility, for a user called user whose user ID is 815:

<?xml version="1.0" encoding="utf-8"?>
	<whitelist>
	  <command name="/usr/libexec/platform-python -s /bin/firewall-cmd*"/>
	  <selinux context="system_u:system_r:NetworkManager_t:s0"/>
	  <user id="815"/>
	  <user name="user"/>
	</whitelist>

This example shows both user id and user name, but only one option is required. Python is the interpreter and is prepended to the command line. You can also use a specific command, for example:

/usr/bin/python3 /bin/firewall-cmd --lockdown-on

In that example, only the --lockdown-on command is allowed.

In Red Hat Enterprise Linux, all utilities are placed in the /usr/bin/ directory and the /bin/ directory is sym-linked to the /usr/bin/ directory. In other words, although the path for firewall-cmd when entered as root might resolve to /bin/firewall-cmd, /usr/bin/firewall-cmd can now be used. All new scripts should use the new location. But be aware that if scripts that run as root are written to use the /bin/firewall-cmd path, then that command path must be added in the allowlist in addition to the /usr/bin/firewall-cmd path traditionally used only for non-root users.

The * at the end of the name attribute of a command means that all commands that start with this string match. If the * is not there then the absolute command including arguments must match.

46.14. Enabling traffic forwarding between different interfaces or sources within a firewalld zone

Intra-zone forwarding is a firewalld feature that enables traffic forwarding between interfaces or sources within a firewalld zone.

46.14.1. The difference between intra-zone forwarding and zones with the default target set to ACCEPT

When intra-zone forwarding is enabled, the traffic within a single firewalld zone can flow from one interface or source to another interface or source. The zone specifies the trust level of interfaces and sources. If the trust level is the same, communication between interfaces or sources is possible.

Note that, if you enable intra-zone forwarding in the default zone of firewalld, it applies only to the interfaces and sources added to the current default zone.

The trusted zone of firewalld uses a default target set to ACCEPT. This zone accepts all forwarded traffic, and intra-zone forwarding is not applicable for it.

As for other default target values, forwarded traffic is dropped by default, which applies to all standard zones except the trusted zone.

46.14.2. Using intra-zone forwarding to forward traffic between an Ethernet and Wi-Fi network

You can use intra-zone forwarding to forward traffic between interfaces and sources within the same firewalld zone. For example, use this feature to forward traffic between an Ethernet network connected to enp1s0 and a Wi-Fi network connected to wlp0s20.

Procedure

Enable packet forwarding in the kernel:

echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf

sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf

Ensure that interfaces between which you want to enable intra-zone forwarding are not assigned to a zone different than the internal zone:
```
# firewall-cmd --get-active-zones
```
If the interface is currently assigned to a zone other than internal, reassign it:
```
# firewall-cmd --zone=internal --change-interface=
interface_name
 --permanent
```

Add the enp1s0 and wlp0s20 interfaces to the internal zone:

# firewall-cmd --zone=internal --add-interface=enp1s0 --add-interface=wlp0s20

Enable intra-zone forwarding:

firewall-cmd --zone=internal --add-forward

Verification

The following verification steps require that the nmap-ncat package is installed on both hosts.

Log in to a host that is in the same network as the enp1s0 interface of the host you enabled zone forwarding on.
Start an echo service with ncat to test connectivity:
```
# ncat -e /usr/bin/cat -l 12345
```
Log in to a host that is in the same network as the wlp0s20 interface.
Connect to the echo server running on the host that is in the same network as the enp1s0:
```
# ncat <other host> 12345
```
Type something and press

Enter

, and verify the text is sent back.

Additional resources

firewalld.zones(5) man page

46.15. Configuring `firewalld` using System Roles

You can use the firewall System Role to configure settings of the firewalld service on multiple clients at once. This solution:

Provides an interface with efficient input settings.
Keeps all intended firewalld parameters in one place.

After you run the firewall role on the control node, the System Role applies the firewalld parameters to the managed node immediately and makes them persistent across reboots.

46.15.1. Introduction to the `firewall` RHEL System Role

RHEL System Roles is a set of contents for the Ansible automation utility. This content together with the Ansible automation utility provides a consistent configuration interface to remotely manage multiple systems.

The rhel-system-roles.firewall role from the RHEL System Roles was introduced for automated configurations of the firewalld service. The rhel-system-roles package contains this System Role, and also the reference documentation.

To apply the firewalld parameters on one or more systems in an automated fashion, use the firewall System Role variable in a playbook. A playbook is a list of one or more plays that is written in the text-based YAML format.

You can use an inventory file to define a set of systems that you want Ansible to configure.

With the firewall role you can configure many different firewalld parameters, for example:

Zones.
The services for which packets should be allowed.
Granting, rejection, or dropping of traffic access to ports.
Forwarding of ports or port ranges for a zone.

Additional resources

README.md and README.html files in the /usr/share/doc/rhel-system-roles/firewall/ directory
Working with playbooks
How to build your inventory

46.15.2. Resetting the firewalld settings using the firewall RHEL System Role

With the firewall RHEL system role, you can reset the firewalld settings to their default state. If you add the previous:replaced parameter to the variable list, the System Role removes all existing user-defined settings and resets firewalld to the defaults. If you combine the previous:replaced parameter with other settings, the firewall role removes all existing settings before applying new ones.

Run this procedure on Ansible control node.

Prerequisites

The ansible and rhel-system-roles packages are installed on the control node.
If you use a different remote user than root when you run the playbook, you must have appropriate sudo permissions on the managed node.
One or more managed nodes that you configure with the firewall RHEL System Role.

Procedure

If the host on which you want to execute the instructions in the playbook is not yet inventoried, add the IP or name of this host to the /etc/ansible/hosts Ansible inventory file:
```
node.example.com
```

Create the ~/reset-firewalld.yml playbook with the following content:

- name: Reset firewalld example
  hosts: node.example.com
  tasks:
    - name: Reset firewalld
      include_role:
        name: rhel-system-roles.firewall
      vars:
        firewall:
          - previous: replaced

Run the playbook:
1. To connect as root user to the managed node:
```
# ansible-playbook -u root ~/reset-firewalld.yml
```
2. To connect as a user to the managed node:
```
# ansible-playbook -u 
user_name
 --ask-become-pass ~/reset-firewalld.yml
```
  The --ask-become-pass option makes sure that the ansible-playbook command prompts for the sudo password of the user defined in the -u user_name option.

If you do not specify the -u user_name option, ansible-playbook connects to the managed node as the user that is currently logged in to the control node.

Verification

Run this command as root on the managed node to check all the zones:
```
# firewall-cmd --list-all-zones
```

Additional resources

/usr/share/ansible/roles/rhel-system-roles.firewall/README.md
ansible-playbook(1)
firewalld(1)

46.15.3. Forwarding incoming traffic from one local port to a different local port

With the firewall role you can remotely configure firewalld parameters with persisting effect on multiple managed hosts.

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on the them.
The hosts or host groups on which you want run this playbook are listed in the Ansible inventory file.

Procedure

Create a playbook file, for example ~/port_forwarding.yml, with the following content:

--- - name: Configure firewalld hosts:

managed-node-01.example.com

tasks: - name: Forward incoming traffic on port 8080 to 443 include_role: name: rhel-system-roles.firewall vars: firewall: - { forward_port: 8080/tcp;443;, state: enabled, runtime: true, permanent: true }

Run the playbook:

ansible-playbook

~/port_forwarding.yml

Verification

On the managed host, display the firewalld settings:
```
# firewall-cmd --list-forward-ports
```

Additional resources

/usr/share/ansible/roles/rhel-system-roles.firewall/README.md

46.15.4. Configuring ports using System Roles

You can use the RHEL firewall System Role to open or close ports in the local firewall for incoming traffic and make the new configuration persist across reboots. For example you can configure the default zone to permit incoming traffic for the HTTPS service.

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on the them.
The hosts or host groups on which you want run this playbook are listed in the Ansible inventory file.

Procedure

Create a playbook file, for example ~/opening-a-port.yml, with the following content:

--- - name: Configure firewalld hosts:

managed-node-01.example.com

tasks: - name: Allow incoming HTTPS traffic to the local host include_role: name: rhel-system-roles.firewall vars: firewall: - port: 443/tcp service: http state: enabled runtime: true permanent: true

The permanent: true option makes the new settings persistent across reboots.

Run the playbook:
```
# ansible-playbook 
~/opening-a-port.yml
```

Verification

On the managed node, verify that the 443/tcp port associated with the HTTPS service is open:
```
# firewall-cmd --list-ports
443/tcp
```

Additional resources

/usr/share/ansible/roles/rhel-system-roles.firewall/README.md

46.15.5. Configuring a DMZ firewalld zone by using the `firewalld` RHEL System Role

As a system administrator, you can use the firewall System Role to configure a dmz zone on the enp1s0 interface to permit HTTPS traffic to the zone. In this way, you enable external users to access your web servers.

Perform this procedure on the Ansible control node.

Prerequisites

You have prepared the control node and the managed nodes
You are logged in to the control node as a user who can run playbooks on the managed nodes.
The account you use to connect to the managed nodes has sudo permissions on the them.
The hosts or host groups on which you want run this playbook are listed in the Ansible inventory file.

Procedure

Create a playbook file, for example ~/configuring-a-dmz.yml, with the following content:

--- - name: Configure firewalld hosts:

managed-node-01.example.com

tasks: - name: Creating a DMZ with access to HTTPS port and masquerading for hosts in DMZ include_role: name: rhel-system-roles.firewall vars: firewall: - zone: dmz interface: enp1s0 service: https state: enabled runtime: true permanent: true

Run the playbook:

ansible-playbook

~/configuring-a-dmz.yml

Verification

On the managed node, view detailed information about the dmz zone:

firewall-cmd --zone=dmz --list-all

dmz (active) target: default icmp-block-inversion: no

interfaces: enp1s0

sources:

services: https

ssh ports: protocols: forward: no masquerade: no forward-ports: source-ports: icmp-blocks:

Additional resources

/usr/share/ansible/roles/rhel-system-roles.firewall/README.md

46.16. Additional resources

firewalld(1) man page
firewalld.conf(5) man page
firewall-cmd(1) man page
firewall-config(1) man page
firewall-offline-cmd(1) man page
firewalld.icmptype(5) man page
firewalld.ipset(5) man page
firewalld.service(5) man page
firewalld.zone(5) man page
firewalld.direct(5) man page
firewalld.lockdown-whitelist(5)
firewalld.richlanguage(5)
firewalld.zones(5) man page
firewalld.dbus(5) man page

Chapter 47. Getting started with nftables

The nftables framework classifies packets and it is the successor to the iptables, ip6tables, arptables, ebtables, and ipset utilities. It offers numerous improvements in convenience, features, and performance over previous packet-filtering tools, most notably:

Built-in lookup tables instead of linear processing
A single framework for both the IPv4 and IPv6 protocols
All rules applied atomically instead of fetching, updating, and storing a complete rule set
Support for debugging and tracing in the rule set (nftrace) and monitoring trace events (in the nft tool)
More consistent and compact syntax, no protocol-specific extensions
A Netlink API for third-party applications

The nftables framework uses tables to store chains. The chains contain individual rules for performing actions. The nft utility replaces all tools from the previous packet-filtering frameworks. You can use the libnftnl library for low-level interaction with nftables Netlink API through the libmnl library.

To display the effect of rule set changes, use the nft list ruleset command. Because these utilities add tables, chains, rules, sets, and other objects to the nftables rule set, be aware that nftables rule-set operations, such as the nft flush ruleset command, might affect rule sets installed using the iptables command.

47.1. Migrating from iptables to nftables

If your firewall configuration still uses iptables rules, you can migrate your iptables rules to nftables.

47.1.1. When to use firewalld, nftables, or iptables

The following is a brief overview in which scenario you should use one of the following utilities:

firewalld: Use the firewalld utility for simple firewall use cases. The utility is easy to use and covers the typical use cases for these scenarios.
nftables: Use the nftables utility to set up complex and performance-critical firewalls, such as for a whole network.
iptables: The iptables utility on Red Hat Enterprise Linux uses the nf_tables kernel API instead of the legacy back end. The nf_tables API provides backward compatibility so that scripts that use iptables commands still work on Red Hat Enterprise Linux. For new firewall scripts, Red Hat recommends to use nftables.

Important

To prevent the different firewall services from influencing each other, run only one of them on a RHEL host, and disable the other services.

47.1.2. Converting iptables and ip6tables rule sets to nftables

Use the iptables-restore-translate and ip6tables-restore-translate utilities to translate iptables and ip6tables rule sets to nftables.

Prerequisites

The nftables and iptables packages are installed.
The system has iptables and ip6tables rules configured.

Procedure

Write the iptables and ip6tables rules to a file:

# iptables-save >/root/iptables.dump
# ip6tables-save >/root/ip6tables.dump

Convert the dump files to nftables instructions:

iptables-restore-translate -f /root/iptables.dump > /etc/nftables/ruleset-migrated-from-iptables.nft

ip6tables-restore-translate -f /root/ip6tables.dump > /etc/nftables/ruleset-migrated-from-ip6tables.nft

Review and, if needed, manually update the generated nftables rules.

To enable the nftables service to load the generated files, add the following to the /etc/sysconfig/nftables.conf file:

include "/etc/nftables/ruleset-migrated-from-iptables.nft"

include "/etc/nftables/ruleset-migrated-from-ip6tables.nft"

Stop and disable the iptables service:
```
# systemctl disable --now iptables
```
If you used a custom script to load the iptables rules, ensure that the script no longer starts automatically and reboot to flush all tables.
Enable and start the nftables service:
```
# systemctl enable --now nftables
```

Verification

Display the nftables rule set:
```
# nft list ruleset
```

Additional resources

Automatically loading nftables rules when the system boots

47.1.3. Converting single iptables and ip6tables rules to nftables

Red Hat Enterprise Linux provides the iptables-translate and ip6tables-translate utilities to convert an iptables or ip6tables rule into the equivalent one for nftables.

Prerequisites

The nftables package is installed.

Procedure

Use the iptables-translate or ip6tables-translate utility instead of iptables or ip6tables to display the corresponding nftables rule, for example:
```
# iptables-translate 
-A INPUT -s 192.0.2.0/24 -j ACCEPT

nft add rule ip filter INPUT ip saddr 192.0.2.0/24 counter accept
```
Note that some extensions lack translation support. In these cases, the utility prints the untranslated rule prefixed with the # sign, for example:
```
# iptables-translate 
-A INPUT -j CHECKSUM --checksum-fill

nft # -A INPUT -j CHECKSUM --checksum-fill
```

Additional resources

iptables-translate --help

47.1.4. Comparison of common iptables and nftables commands

The following is a comparison of common iptables and nftables commands:

Listing all rules:

iptablesnftables

iptables-save

nft list ruleset
Listing a certain table and chain:

iptablesnftables

iptables -L

nft list table ip filter

iptables -L INPUT

nft list chain ip filter INPUT

iptables -t nat -L PREROUTING

nft list chain ip nat PREROUTING

The nft command does not pre-create tables and chains. They exist only if a user created them manually.

Example: Listing rules generated by firewalld
```
# nft list table inet firewalld
# nft list table ip firewalld
# nft list table ip6 firewalld
```

47.1.5. Additional resources

iptables: The two variants and their relationship with nftables

47.2. Writing and executing nftables scripts

The major benefit of using the nftables` framework is that the execution of scripts is atomic. This means that the system either applies the whole script or prevents the execution if an error occurs. This guarantees that the firewall is always in a consistent state.

Additionally, with the nftables script environment, you can:

Add comments
Define variables
Include other rule-set files

When you install the nftables package, Red Hat Enterprise Linux automatically creates *.nft scripts in the /etc/nftables/ directory. These scripts contain commands that create tables and empty chains for different purposes.

47.2.1. Supported nftables script formats

You can write scripts in the nftables scripting environment in the following formats:

The same format as the nft list ruleset command displays the rule set:

#!/usr/sbin/nft -f

# Flush the rule set
flush ruleset

table inet example_table {
  chain example_chain {
    # Chain for incoming packets that drops all packets that
    # are not explicitly allowed by any rule in this chain
    type filter hook input priority 0; policy drop;

    # Accept connections to port 22 (ssh)
    tcp dport ssh accept
  }
}

The same syntax as for nft commands:

#!/usr/sbin/nft -f

# Flush the rule set
flush ruleset

# Create a table
add table inet example_table

# Create a chain for incoming packets that drops all packets
# that are not explicitly allowed by any rule in this chain
add chain inet example_table example_chain { type filter hook input priority 0 ; policy drop ; }

# Add a rule that accepts connections to port 22 (ssh)
add rule inet example_table example_chain tcp dport ssh accept

47.2.2. Running nftables scripts

You can run an nftables script either by passing it to the nft utility or by executing the script directly.

Procedure

To run an nftables script by passing it to the nft utility, enter:
```
# nft -f /etc/nftables/<example_firewall_script>.nft
```
To run an nftables script directly:
1. For the single time that you perform this:
  1. Ensure that the script starts with the following shebang sequence:
```
#!/usr/sbin/nft -f
```
    Important
    
    If you omit the -f parameter, the nft utility does not read the script and displays: Error: syntax error, unexpected newline, expecting string.
  2. Optional: Set the owner of the script to root:
```
# chown root /etc/nftables/<example_firewall_script>.nft
```
  3. Make the script executable for the owner:
```
# chmod u+x /etc/nftables/<example_firewall_script>.nft
```
2. Run the script:
```
# /etc/nftables/<example_firewall_script>.nft
```
  If no output is displayed, the system executed the script successfully.

Important

Even if nft executes the script successfully, incorrectly placed rules, missing parameters, or other problems in the script can cause that the firewall behaves not as expected.

Additional resources

chown(1) man page
chmod(1) man page
Automatically loading nftables rules when the system boots

47.2.4. Using variables in nftables script

To define a variable in an nftables script, use the define keyword. You can store single values and anonymous sets in a variable. For more complex scenarios, use sets or verdict maps.

Variables with a single value

The following example defines a variable named INET_DEV with the value enp1s0:

define INET_DEV = enp1s0

You can use the variable in the script by entering the $ sign followed by the variable name:

... add rule inet example_table example_chain iifname

$INET_DEV

tcp dport ssh accept ...

Variables that contain an anonymous set

The following example defines a variable that contains an anonymous set:

define DNS_SERVERS = { 192.0.2.1
, 192.0.2.2
 }

You can use the variable in the script by writing the $ sign followed by the variable name:

add rule inet example_table example_chain ip daddr

$DNS_SERVERS

Note

Curly braces have special semantics when you use them in a rule because they indicate that the variable represents a set.

Additional resources

Using sets in nftables commands
Using verdict maps in nftables commands

47.2.5. Including files in nftables scripts

In the nftables scripting environment, you can include other scripts by using the include statement.

If you specify only a file name without an absolute or relative path, nftables includes files from the default search path, which is set to /etc on Red Hat Enterprise Linux.

Example 47.2. Including files from the default search directory

To include a file from the default search directory:

include "example.nft"

Example 47.3. Including all *.nft files from a directory

To include all files ending with *.nft that are stored in the /etc/nftables/rulesets/ directory:

include "/etc/nftables/rulesets/*.nft"

Note that the include statement does not match files beginning with a dot.

Additional resources

The Include files section in the nft(8) man page

47.2.6. Automatically loading nftables rules when the system boots

The nftables systemd service loads firewall scripts that are included in the /etc/sysconfig/nftables.conf file.

Prerequisites

The nftables scripts are stored in the /etc/nftables/ directory.

Procedure

Edit the /etc/sysconfig/nftables.conf file.
- If you modified the *.nft scripts that were created in /etc/nftables/ with the installation of the nftables package, uncomment the include statement for these scripts.
- If you wrote new scripts, add include statements to include these scripts. For example, to load the /etc/nftables/example.nft script when the nftables service starts, add:
```
include "/etc/nftables/example
.nft"
```
Optional: Start the nftables service to load the firewall rules without rebooting the system:
```
# systemctl start nftables
```
Enable the nftables service.
```
# systemctl enable nftables
```

Additional resources

Supported nftables script formats

47.3. Creating and managing nftables tables, chains, and rules

You can display nftables rule sets and manage them.

47.3.1. Basics of nftables tables

A table in nftables is a namespace that contains a collection of chains, rules, sets, and other objects.

Each table must have an address family assigned. The address family defines the packet types that this table processes. You can set one of the following address families when you create a table:

ip: Matches only IPv4 packets. This is the default if you do not specify an address family.
ip6: Matches only IPv6 packets.
inet: Matches both IPv4 and IPv6 packets.
arp: Matches IPv4 address resolution protocol (ARP) packets.
bridge: Matches packets that pass through a bridge device.
netdev: Matches packets from ingress.

If you want to add a table, the format to use depends on your firewall script:

In scripts in native syntax, use:

table 
<table_address_family>
 <table_name>
 {
}

In shell scripts, use:

nft add table 
<table_address_family>
 <table_name>

47.3.2. Basics of nftables chains

Tables consist of chains which in turn are containers for rules. The following two rule types exists:

Base chain

: You can use base chains as an entry point for packets from the networking stack.
Regular chain

: You can use regular chains as a jump target to better organize rules.

If you want to add a base chain to a table, the format to use depends on your firewall script:

In scripts in native syntax, use:

table <table_address_family>
 <table_name> {
  chain 
<chain_name>
 {
    type 
<type>
 hook <hook>
 priority <priority>
    policy 
<policy>
 ;
  }
}

In shell scripts, use:
```
nft add chain 
<table_address_family>
 <table_name>
 <chain_name>
 { type <type>
 hook <hook>
 priority <priority>
 \; policy <policy>
 \; }
```
To avoid that the shell interprets the semicolons as the end of the command, place the \ escape character in front of the semicolons.

Both examples create base chains. To create a regular chain, do not set any parameters in the curly brackets.

Chain types

The following are the chain types and an overview with which address families and hooks you can use them:

TypeAddress familiesHooksDescription

filter

all

Standard chain type

nat

ip, ip6, inet

prerouting, input, output, postrouting

Chains of this type perform native address translation based on connection tracking entries. Only the first packet traverses this chain type.

route

ip, ip6

output

Accepted packets that traverse this chain type cause a new route lookup if relevant parts of the IP header have changed.

Chain priorities

The priority parameter specifies the order in which packets traverse chains with the same hook value. You can set this parameter to an integer value or use a standard priority name.

The following matrix is an overview of the standard priority names and their numeric values, and with which address families and hooks you can use them:

Textual valueNumeric valueAddress familiesHooks

raw

-300

ip, ip6, inet

all

mangle

-150

ip, ip6, inet

all

dstnat

-100

ip, ip6, inet

prerouting

-300

bridge

prerouting

filter

0

ip, ip6, inet, arp, netdev

all

-200

bridge

all

security

50

ip, ip6, inet

all

srcnat

100

ip, ip6, inet

postrouting

300

bridge

postrouting

out

100

bridge

output

Chain policies

The chain policy defines whether nftables should accept or drop packets if rules in this chain do not specify any action. You can set one of the following policies in a chain:

accept (default)
drop

47.3.3. Basics of nftables rules

Rules define actions to perform on packets that pass a chain that contains this rule. If the rule also contains matching expressions, nftables performs the actions only if all previous expressions apply.

If you want to add a rule to a chain, the format to use depends on your firewall script:

In scripts in native syntax, use:

table <table_address_family>
 <table_name> {
  chain <chain_name> {
    type <type>
 hook <hook>
 priority <priority>
 ; policy <policy> ;
      
<rule>

  }
}

In shell scripts, use:
```
nft add rule 
<table_address_family>
 <table_name>
 <chain_name>
 <rule>
```
This shell command appends the new rule at the end of the chain. If you prefer to add a rule at the beginning of the chain, use the nft insert command instead of nft add.

47.3.4. Managing tables, chains, and rules using nft commands

To manage an nftables firewall on the command line or in shell scripts, use the nft utility.

Important

The commands in this procedure do not represent a typical workflow and are not optimized. This procedure only demonstrates how to use nft commands to manage tables, chains, and rules in general.

Procedure

Create a table named nftables_svc with the inet address family so that the table can process both IPv4 and IPv6 packets:
```
# nft add table inet 
nftables_svc
```
Add a base chain named INPUT, that processes incoming network traffic, to the inet nftables_svc table:
```
# nft add chain inet 
nftables_svc
 INPUT
 { type filter
 hook input
 priority filter
 \; policy accept
 \; }
```
To avoid that the shell interprets the semicolons as the end of the command, escape the semicolons using the \ character.
Add rules to the INPUT chain. For example, allow incoming TCP traffic on port 22 and 443, and, as the last rule of the INPUT chain, reject other incoming traffic with an Internet Control Message Protocol (ICMP) port unreachable message:
```
# nft add rule inet 
nftables_svc
 INPUT
 tcp dport 22 accept
# nft add rule inet 
nftables_svc
 INPUT
 tcp dport 443 accept
# nft add rule inet 
nftables_svc
 INPUT
 reject with icmpx type port-unreachable
```
If you enter the nft add rule commands as shown, nft adds the rules in the same order to the chain as you run the commands.

Display the current rule set including handles:

nft -a list table inet

nftables_svc

table inet

nftables_svc

{ # handle

chain

INPUT

{ # handle

type

filter

hook

input

priority

filter

; policy

; tcp dport 22 accept # handle

tcp dport 443 accept # handle

reject # handle

} }

Insert a rule before the existing rule with handle 3. For example, to insert a rule that allows TCP traffic on port 636, enter:
```
# nft insert rule inet 
nftables_svc
 INPUT
 position 3 tcp dport 636 accept
```
Append a rule after the existing rule with handle 3. For example, to insert a rule that allows TCP traffic on port 80, enter:
```
# nft add rule inet 
nftables_svc
 INPUT
 position 3
 tcp dport 80 accept
```

Display the rule set again with handles. Verify that the later added rules have been added to the specified positions:

nft -a list table inet

nftables_svc

table inet

nftables_svc

{ # handle

chain

INPUT

{ # handle

type

filter

hook

input

priority

filter

; policy

; tcp dport 22 accept # handle

tcp dport 636 accept # handle

tcp dport 443 accept # handle

tcp dport 80 accept # handle

reject # handle

} }

Remove the rule with handle 6:
```
# nft delete rule inet 
nftables_svc
 INPUT
 handle 6
```
To remove a rule, you must specify the handle.

Display the rule set, and verify that the removed rule is no longer present:

nft -a list table inet

nftables_svc

table inet

nftables_svc

{ # handle

chain

INPUT

{ # handle

type

filter

hook

input

priority

filter

; policy

; tcp dport 22 accept # handle

tcp dport 636 accept # handle

tcp dport 443 accept # handle

reject # handle

} }

Remove all remaining rules from the INPUT chain:
```
# nft flush chain inet 
nftables_svc
 INPUT
```

Display the rule set, and verify that the INPUT chain is empty:

# nft list table inet 
nftables_svc

table inet nftables_svc {
  chain INPUT {
    type filter hook input priority filter; policy accept
  }
}

Delete the INPUT chain:
```
# nft delete chain inet 
nftables_svc
 INPUT
```
You can also use this command to delete chains that still contain rules.
Display the rule set, and verify that the INPUT chain has been deleted:
```
# nft list table inet 
nftables_svc

table inet nftables_svc {
}
```
Delete the nftables_svc table:
```
# nft delete table inet 
nftables_svc
```
You can also use this command to delete tables that still contain chains.

Note

To delete the entire rule set, use the nft flush ruleset command instead of manually deleting all rules, chains, and tables in separate commands.

Additional resources

nft(8) man page

47.4. Configuring NAT using nftables

With nftables, you can configure the following network address translation (NAT) types:

Masquerading
Source NAT (SNAT)
Destination NAT (DNAT)
Redirect

Important

You can only use real interface names in iifname and oifname parameters, and alternative names (altname) are not supported.

47.4.1. NAT types

These are the different network address translation (NAT) types:

Masquerading and source NAT (SNAT)

Masquerading and SNAT are very similar to one another. The differences are:

Masquerading automatically uses the IP address of the outgoing interface. Therefore, use masquerading if the outgoing interface uses a dynamic IP address.
SNAT sets the source IP address of packets to a specified IP and does not dynamically look up the IP of the outgoing interface. Therefore, SNAT is faster than masquerading. Use SNAT if the outgoing interface uses a fixed IP address.

Destination NAT (DNAT)

Redirect

47.4.2. Configuring masquerading using nftables

Masquerading enables a router to dynamically change the source IP of packets sent through an interface to the IP address of the interface. This means that if the interface gets a new IP assigned, nftables automatically uses the new IP when replacing the source IP.

Replace the source IP of packets leaving the host through the ens3 interface to the IP set on ens3.

Procedure

Create a table:
```
# nft add table nat
```
Add the prerouting and postrouting chains to the table:
```
# nft add chain nat postrouting { type nat hook postrouting priority 100 \; }
```
Important

Even if you do not add a rule to the prerouting chain, the nftables framework requires this chain to match incoming packet replies.

Note that you must pass the -- option to the nft command to prevent the shell from interpreting the negative priority value as an option of the nft command.
Add a rule to the postrouting chain that matches outgoing packets on the ens3 interface:
```
# nft add rule nat postrouting oifname "ens3
" masquerade
```

47.4.3. Configuring source NAT using nftables

On a router, Source NAT (SNAT) enables you to change the IP of packets sent through an interface to a specific IP address. The router then replaces the source IP of outgoing packets.

Procedure

Create a table:
```
# nft add table nat
```
Add the prerouting and postrouting chains to the table:
```
# nft add chain nat postrouting { type nat hook postrouting priority 100 \; }
```
Important

Even if you do not add a rule to the postrouting chain, the nftables framework requires this chain to match outgoing packet replies.

Note that you must pass the -- option to the nft command to prevent the shell from interpreting the negative priority value as an option of the nft command.
Add a rule to the postrouting chain that replaces the source IP of outgoing packets through ens3 with 192.0.2.1:
```
# nft add rule nat postrouting oifname "ens3
" snat to 192.0.2.1
```

Additional resources

Forwarding incoming packets on a specific local port to a different host

47.4.4. Configuring destination NAT using nftables

Destination NAT (DNAT) enables you to redirect traffic on a router to a host that is not directly accessible from the Internet.

For example, with DNAT the router redirects incoming traffic sent to port 80 and 443 to a web server with the IP address 192.0.2.1.

Procedure

Create a table:
```
# nft add table nat
```
Add the prerouting and postrouting chains to the table:
```
# nft -- add chain nat prerouting { type nat hook prerouting priority -100 \; }
# nft add chain nat postrouting { type nat hook postrouting priority 100 \; }
```
Important

Even if you do not add a rule to the postrouting chain, the nftables framework requires this chain to match outgoing packet replies.

Note that you must pass the -- option to the nft command to prevent the shell from interpreting the negative priority value as an option of the nft command.
Add a rule to the prerouting chain that redirects incoming traffic to port 80 and 443 on the ens3 interface of the router to the web server with the IP address 192.0.2.1:”
```
# nft add rule nat prerouting iifname ens3
 tcp dport { 80, 443 } dnat to 192.0.2.1
```
Depending on your environment, add either a SNAT or masquerading rule to change the source address for packets returning from the web server to the sender:
1. If the ens3 interface uses a dynamic IP addresses, add a masquerading rule:
```
# nft add rule nat postrouting oifname "ens3" masquerade
```
2. If the ens3 interface uses a static IP address, add a SNAT rule. For example, if the ens3 uses the 198.51.100.1 IP address:
```
# nft add rule nat postrouting oifname "ens3" snat to 198.51.100.1
```

Enable packet forwarding:

# echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf
# sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf

Additional resources

NAT types

47.4.5. Configuring a redirect using nftables

The redirect feature is a special case of destination network address translation (DNAT) that redirects packets to the local machine depending on the chain hook.

For example, you can redirect incoming and forwarded traffic sent to port 22 of the local host to port 2222.

Procedure

Create a table:
```
# nft add table nat
```
Add the prerouting chain to the table:
```
# nft -- add chain nat prerouting { type nat hook prerouting priority -100 \; }
```
Note that you must pass the -- option to the nft command to prevent the shell from interpreting the negative priority value as an option of the nft command.
Add a rule to the prerouting chain that redirects incoming traffic on port 22 to port 2222:
```
# nft add rule nat prerouting tcp dport 22 redirect to 2222
```

Additional resources

NAT types

47.5. Using sets in nftables commands

The nftables framework natively supports sets. You can use sets, for example, if a rule should match multiple IP addresses, port numbers, interfaces, or any other match criteria.

47.5.1. Using anonymous sets in nftables

An anonymous set contains comma-separated values enclosed in curly brackets, such as { 22, 80, 443 }, that you use directly in a rule. You can use anonymous sets also for IP addresses and any other match criteria.

The drawback of anonymous sets is that if you want to change the set, you must replace the rule. For a dynamic solution, use named sets as described in Using named sets in nftables.

Prerequisites

The example_chain chain and the example_table table in the inet family exists.

Procedure

For example, to add a rule to example_chain in example_table that allows incoming traffic to port 22, 80, and 443:
```
# nft add rule inet
 example_table
 example_chain
 tcp dport { 22, 80, 443 } accept
```

Optional: Display all chains and their rules in example_table:

# nft list table inet example_table
table inet example_table {
  chain example_chain {
    type filter hook input priority filter; policy accept;
    tcp dport { ssh, http, https } accept
  }
}

47.5.2. Using named sets in nftables

The nftables framework supports mutable named sets. A named set is a list or range of elements that you can use in multiple rules within a table. Another benefit over anonymous sets is that you can update a named set without replacing the rules that use the set.

When you create a named set, you must specify the type of elements the set contains. You can set the following types:

ipv4_addr for a set that contains IPv4 addresses or ranges, such as 192.0.2.1 or 192.0.2.0/24.
ipv6_addr for a set that contains IPv6 addresses or ranges, such as 2001:db8:1::1 or 2001:db8:1::1/64.
ether_addr for a set that contains a list of media access control (MAC) addresses, such as 52:54:00:6b:66:42.
inet_proto for a set that contains a list of Internet protocol types, such as tcp.
inet_service for a set that contains a list of Internet services, such as ssh.
mark for a set that contains a list of packet marks. Packet marks can be any positive 32-bit integer value (0 to 2147483647).

Prerequisites

The example_chain chain and the example_table table exists.

Procedure

Create an empty set. The following examples create a set for IPv4 addresses:
- To create a set that can store multiple individual IPv4 addresses:
```
# nft add set inet
 example_table
 example_set
 { type ipv4_addr \; }
```
- To create a set that can store IPv4 address ranges:
```
# nft add set inet
 example_table
 example_set
 { type ipv4_addr \; flags interval \; }
```
Important

To prevent the shell from interpreting the semicolons as the end of the command, you must escape the semicolons with a backslash.
Optional: Create rules that use the set. For example, the following command adds a rule to the example_chain in the example_table that will drop all packets from IPv4 addresses in example_set.
```
# nft add rule inet
 example_table
 example_chain
 ip saddr @example_set
 drop
```
Because example_set is still empty, the rule has currently no effect.
Add IPv4 addresses to example_set:
- If you create a set that stores individual IPv4 addresses, enter:
```
# nft add element inet
 example_table
 example_set
 { 192.0.2.1, 192.0.2.2
 }
```
- If you create a set that stores IPv4 ranges, enter:
```
# nft add element inet
 example_table
 example_set
 { 192.0.2.0-192.0.2.255
 }
```
  When you specify an IP address range, you can alternatively use the Classless Inter-Domain Routing (CIDR) notation, such as 192.0.2.0/24 in the above example.

47.5.3. Additional resources

The Sets section in the nft(8) man page

47.6. Using verdict maps in nftables commands

Verdict maps, which are also known as dictionaries, enable nft to perform an action based on packet information by mapping match criteria to an action.

47.6.1. Using anonymous maps in nftables

An anonymous map is a { match_criteria : action } statement that you use directly in a rule. The statement can contain multiple comma-separated mappings.

The drawback of an anonymous map is that if you want to change the map, you must replace the rule. For a dynamic solution, use named maps as described in Using named maps in nftables.

For example, you can use an anonymous map to route both TCP and UDP packets of the IPv4 and IPv6 protocol to different chains to count incoming TCP and UDP packets separately.

Procedure

Create a new table:
```
# nft add table inet example_table
```

Create the tcp_packets chain in example_table:

# nft add chain inet example_table tcp_packets

Add a rule to tcp_packets that counts the traffic in this chain:
```
# nft add rule inet example_table tcp_packets counter
```

Create the udp_packets chain in example_table

# nft add chain inet example_table udp_packets

Add a rule to udp_packets that counts the traffic in this chain:
```
# nft add rule inet example_table udp_packets counter
```
Create a chain for incoming traffic. For example, to create a chain named incoming_traffic in example_table that filters incoming traffic:
```
# nft add chain inet example_table incoming_traffic { type filter hook input priority 0 \; }
```
Add a rule with an anonymous map to incoming_traffic:
```
# nft add rule inet example_table incoming_traffic ip protocol vmap { tcp : jump tcp_packets, udp : jump udp_packets }
```
The anonymous map distinguishes the packets and sends them to the different counter chains based on their protocol.

To list the traffic counters, display example_table:

# nft list table inet example_table
table inet example_table {
  chain tcp_packets {
    counter packets 36379 bytes 2103816
  }

  chain udp_packets {
    counter packets 10 bytes 1559
  }

  chain incoming_traffic {
    type filter hook input priority filter; policy accept;
    ip protocol vmap { tcp : jump tcp_packets, udp : jump udp_packets }
  }
}

The counters in the tcp_packets and udp_packets chain display both the number of received packets and bytes.

47.6.2. Using named maps in nftables

The nftables framework supports named maps. You can use these maps in multiple rules within a table. Another benefit over anonymous maps is that you can update a named map without replacing the rules that use it.

When you create a named map, you must specify the type of elements:

ipv4_addr for a map whose match part contains an IPv4 address, such as 192.0.2.1.
ipv6_addr for a map whose match part contains an IPv6 address, such as 2001:db8:1::1.
ether_addr for a map whose match part contains a media access control (MAC) address, such as 52:54:00:6b:66:42.
inet_proto for a map whose match part contains an Internet protocol type, such as tcp.
inet_service for a map whose match part contains an Internet services name port number, such as ssh or 22.
mark for a map whose match part contains a packet mark. A packet mark can be any positive 32-bit integer value (0 to 2147483647).
counter for a map whose match part contains a counter value. The counter value can be any positive 64-bit integer value.
quota for a map whose match part contains a quota value. The quota value can be any positive 64-bit integer value.

For example, you can allow or drop incoming packets based on their source IP address. Using a named map, you require only a single rule to configure this scenario while the IP addresses and actions are dynamically stored in the map.

Procedure

Create a table. For example, to create a table named example_table that processes IPv4 packets:
```
# nft add table ip example_table
```
Create a chain. For example, to create a chain named example_chain in example_table:
```
# nft add chain ip example_table
 example_chain
 { type filter hook input
 priority 0 \; }
```
Important

To prevent the shell from interpreting the semicolons as the end of the command, you must escape the semicolons with a backslash.

Create an empty map. For example, to create a map for IPv4 addresses:

# nft add map ip example_table
 example_map
 { type ipv4_addr : verdict \; }

Create rules that use the map. For example, the following command adds a rule to example_chain in example_table that applies actions to IPv4 addresses which are both defined in example_map:
```
# nft add rule example_table
 example_chain
 ip saddr vmap @example_map
```
Add IPv4 addresses and corresponding actions to example_map:
```
# nft add element ip example_table
 example_map
 { 192.0.2.1 : accept, 192.0.2.2 : drop }
```
This example defines the mappings of IPv4 addresses to actions. In combination with the rule created above, the firewall accepts packet from 192.0.2.1 and drops packets from 192.0.2.2.
Optional: Enhance the map by adding another IP address and action statement:
```
# nft add element ip example_table
 example_map
 { 192.0.2.3 : accept }
```

Optional: Remove an entry from the map:

# nft delete element ip example_table
 example_map
 { 192.0.2.1 }

Optional: Display the rule set:

# nft list ruleset
table ip example_table {
  map example_map {
    type ipv4_addr : verdict
    elements = { 192.0.2.2 : drop, 192.0.2.3 : accept }
  }

  chain example_chain {
    type filter hook input priority filter; policy accept;
    ip saddr vmap @example_map
  }
}

47.6.3. Additional resources

The Maps section in the nft(8) man page

47.7. Example: Protecting a LAN and DMZ using an nftables script

Use the nftables framework on a RHEL router to write and install a firewall script that protects the network clients in an internal LAN and a web server in a DMZ from unauthorized access from the Internet and from other networks.

Important

This example is only for demonstration purposes and describes a scenario with specific requirements.

Firewall scripts highly depend on the network infrastructure and security requirements. Use this example to learn the concepts of nftables firewalls when you write scripts for your own environment.

47.7.1. Network conditions

The network in this example has the following conditions:

The router is connected to the following networks:
- The Internet through interface enp1s0
- The internal LAN through interface enp7s0
- The DMZ through enp8s0
The Internet interface of the router has both a static IPv4 address (203.0.113.1) and IPv6 address (2001:db8:a::1) assigned.
The clients in the internal LAN use only private IPv4 addresses from the range 10.0.0.0/24. Consequently, traffic from the LAN to the Internet requires source network address translation (SNAT).
The administrator PCs in the internal LAN use the IP addresses 10.0.0.100 and 10.0.0.200.
The DMZ uses public IP addresses from the ranges 198.51.100.0/24 and 2001:db8:b::/56.
The web server in the DMZ uses the IP addresses 198.51.100.5 and 2001:db8:b::5.
The router acts as a caching DNS server for hosts in the LAN and DMZ.

47.7.2. Security requirements to the firewall script

The following are the requirements to the nftables firewall in the example network:

The router must be able to:
- Recursively resolve DNS queries.
- Perform all connections on the loopback interface.
Clients in the internal LAN must be able to:
- Query the caching DNS server running on the router.
- Access the HTTPS server in the DMZ.
- Access any HTTPS server on the Internet.
The PCs of the administrators must be able to access the router and every server in the DMZ using SSH.
The web server in the DMZ must be able to:
- Query the caching DNS server running on the router.
- Access HTTPS servers on the Internet to download updates.
Hosts on the Internet must be able to:
- Access the HTTPS servers in the DMZ.
Additionally, the following security requirements exists:
- Connection attempts that are not explicitly allowed should be dropped.
- Dropped packets should be logged.

47.7.3. Configuring logging of dropped packets to a file

By default, systemd logs kernel messages, such as for dropped packets, to the journal. Additionally, you can configure the rsyslog service to log such entries to a separate file. To ensure that the log file does not grow infinitely, configure a rotation policy.

Prerequisites

The rsyslog package is installed.
The rsyslog service is running.

Procedure

Create the /etc/rsyslog.d/nftables.conf file with the following content:
```
:msg, startswith, "nft drop" -/var/log/nftables.log
& stop
```
Using this configuration, the rsyslog service logs dropped packets to the /var/log/nftables.log file instead of /var/log/messages.
Restart the rsyslog service:
```
# systemctl restart rsyslog
```
Create the /etc/logrotate.d/nftables file with the following content to rotate /var/log/nftables.log if the size exceeds 10 MB:
```
/var/log/nftables.log {
  size +10M
  maxage 30
  sharedscripts
  postrotate
    /usr/bin/systemctl kill -s HUP rsyslog.service >/dev/null 2>&1 || true
  endscript
}
```
The maxage 30 setting defines that logrotate removes rotated logs older than 30 days during the next rotation operation.

Additional resources

rsyslog.conf(5) man page
logrotate(8) man page

47.7.4. Writing and activating the nftables script

This example is an nftables firewall script that runs on a RHEL router and protects the clients in an internal LAN and a web server in a DMZ. For details about the network and the requirements for the firewall used in the example, see Network conditions and Security requirements to the firewall script.

Warning

This nftables firewall script is only for demonstration purposes. Do not use it without adapting it to your environments and security requirements.

Prerequisites

The network is configured as described in Network conditions.

Procedure

Create the /etc/nftables/firewall.nft script with the following content:

# Remove all rules
flush ruleset


# Table for both IPv4 and IPv6 rules
table inet nftables_svc {

  # Define variables for the interface name
  define INET_DEV = enp1s0
  define LAN_DEV  = enp7s0
  define DMZ_DEV  = enp8s0


  # Set with the IPv4 addresses of admin PCs
  set admin_pc_ipv4 {
    type ipv4_addr
    elements = { 10.0.0.100, 10.0.0.200 }
  }


  # Chain for incoming trafic. Default policy: drop
  chain INPUT {
    type filter hook input priority filter
    policy drop

    # Accept packets in established and related state, drop invalid packets
    ct state vmap { established:accept, related:accept, invalid:drop }

    # Accept incoming traffic on loopback interface
    iifname lo accept

    # Allow request from LAN and DMZ to local DNS server
    iifname { $LAN_DEV, $DMZ_DEV } meta l4proto { tcp, udp } th dport 53 accept

    # Allow admins PCs to access the router using SSH
    iifname $LAN_DEV ip saddr @admin_pc_ipv4 tcp dport 22 accept

    # Last action: Log blocked packets
    # (packets that were not accepted in previous rules in this chain)
    log prefix "nft drop IN : "
  }


  # Chain for outgoing traffic. Default policy: drop
  chain OUTPUT {
    type filter hook output priority filter
    policy drop

    # Accept packets in established and related state, drop invalid packets
    ct state vmap { established:accept, related:accept, invalid:drop }

    # Accept outgoing traffic on loopback interface
    oifname lo accept

    # Allow local DNS server to recursively resolve queries
    oifname $INET_DEV meta l4proto { tcp, udp } th dport 53 accept

    # Last action: Log blocked packets
    log prefix "nft drop OUT: "
  }


  # Chain for forwarding traffic. Default policy: drop
  chain FORWARD {
    type filter hook forward priority filter
    policy drop

    # Accept packets in established and related state, drop invalid packets
    ct state vmap { established:accept, related:accept, invalid:drop }

    # IPv4 access from LAN and Internet to the HTTPS server in the DMZ
    iifname { $LAN_DEV, $INET_DEV } oifname $DMZ_DEV ip daddr 198.51.100.5 tcp dport 443 accept

    # IPv6 access from Internet to the HTTPS server in the DMZ
    iifname $INET_DEV oifname $DMZ_DEV ip6 daddr 2001:db8:b::5 tcp dport 443 accept

    # Access from LAN and DMZ to HTTPS servers on the Internet
    iifname { $LAN_DEV, $DMZ_DEV } oifname $INET_DEV tcp dport 443 accept

    # Last action: Log blocked packets
    log prefix "nft drop FWD: "
  }


  # Postrouting chain to handle SNAT
  chain postrouting {
    type nat hook postrouting priority srcnat; policy accept;

    # SNAT for IPv4 traffic from LAN to Internet
    iifname $LAN_DEV oifname $INET_DEV snat ip to 203.0.113.1
  }
}

Include the /etc/nftables/firewall.nft script in the /etc/sysconfig/nftables.conf file:
```
include "/etc/nftables/firewall.nft"
```

Enable IPv4 forwarding:

echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf

sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf

Enable and start the nftables service:
```
# systemctl enable --now nftables
```

Verification

Optional: Verify the nftables rule set:
```
# nft list ruleset
...
```
Try to perform an access that the firewall prevents. For example, try to access the router using SSH from the DMZ:
```
# ssh router.example.com
ssh: connect to host router.example.com
 port 22
: Network is unreachable
```

Depending on your logging settings, search:

The systemd journal for the blocked packets:

# journalctl -k -g "nft drop"
Oct 14 17:27:18 router kernel: nft drop IN : IN=enp8s0 OUT= MAC=... SRC=198.51.100.5 DST=198.51.100.1 ... PROTO=TCP SPT=40464 DPT=22 ... SYN ...

The /var/log/nftables.log file for the blocked packets:

Oct 14 17:27:18 router kernel: nft drop IN : IN=enp8s0 OUT= MAC=... SRC=198.51.100.5 DST=198.51.100.1 ... PROTO=TCP SPT=40464 DPT=22 ... SYN ...

47.8. Configuring port forwarding using nftables

Port forwarding enables administrators to forward packets sent to a specific destination port to a different local or remote port.

For example, if your web server does not have a public IP address, you can set a port forwarding rule on your firewall that forwards incoming packets on port 80 and 443 on the firewall to the web server. With this firewall rule, users on the internet can access the web server using the IP or host name of the firewall.

47.8.1. Forwarding incoming packets to a different local port

You can use nftables to forward packets. For example, you can forward incoming IPv4 packets on port 8022 to port 22 on the local system.

Procedure

Create a table named nat with the ip address family:
```
# nft add table ip nat
```
Add the prerouting and postrouting chains to the table:
```
# nft -- add chain ip nat prerouting { type nat hook prerouting priority -100 \; }
```
Note

Pass the -- option to the nft command to prevent the shell from interpreting the negative priority value as an option of the nft command.
Add a rule to the prerouting chain that redirects incoming packets on port 8022 to the local port 22:
```
# nft add rule ip nat prerouting tcp dport 8022 redirect to :22
```

47.8.2. Forwarding incoming packets on a specific local port to a different host

You can use a destination network address translation (DNAT) rule to forward incoming packets on a local port to a remote host. This enables users on the Internet to access a service that runs on a host with a private IP address.

For example, you can forward incoming IPv4 packets on the local port 443 to the same port number on the remote system with the 192.0.2.1 IP address.

Prerequisites

You are logged in as the root user on the system that should forward the packets.

Procedure

Create a table named nat with the ip address family:
```
# nft add table ip nat
```
Add the prerouting and postrouting chains to the table:
```
# nft -- add chain ip nat prerouting { type nat hook prerouting priority -100 \; }
# nft add chain ip nat postrouting { type nat hook postrouting priority 100 \; }
```
Note

Pass the -- option to the nft command to prevent the shell from interpreting the negative priority value as an option of the nft command.
Add a rule to the prerouting chain that redirects incoming packets on port 443 to the same port on 192.0.2.1:
```
# nft add rule ip nat prerouting tcp dport 443 dnat to 192.0.2.1
```
Add a rule to the postrouting chain to masquerade outgoing traffic:
```
# nft add rule ip nat postrouting daddr 192.0.2.1 masquerade
```

Enable packet forwarding:

# echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf
# sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf

47.9. Using nftables to limit the amount of connections

You can use nftables to limit the number of connections or to block IP addresses that attempt to establish a given amount of connections to prevent them from using too many system resources.

47.9.1. Limiting the number of connections using nftables

The ct count parameter of the nft utility enables administrators to limit the number of connections.

Prerequisites

The base example_chain in example_table exists.

Procedure

Create a dynamic set for IPv4 addresses:

# nft add set inet example_table example_meter { type ipv4_addr\; flags dynamic \;}

Add a rule that allows only two simultaneous connections to the SSH port (22) from an IPv4 address and rejects all further connections from the same IP:
```
# nft add rule ip example_table
 example_chain
 tcp dport ssh meter example_meter
 { ip saddr ct count over 2 } counter reject
```
Optional: Display the set created in the previous step:
```
# nft list set inet example_table
 example_meter
table inet example_table {
  meter example_meter {
    type ipv4_addr
    size 65535
    elements = { 192.0.2.1
 ct count over 2 , 192.0.2.2 ct count over 2  }
  }
}
```
The elements entry displays addresses that currently match the rule. In this example, elements lists IP addresses that have active connections to the SSH port. Note that the output does not display the number of active connections or if connections were rejected.

47.9.2. Blocking IP addresses that attempt more than ten new incoming TCP connections within one minute

You can temporarily block hosts that are establishing more than ten IPv4 TCP connections within one minute.

Procedure

Create the filter table with the ip address family:
```
# nft add table ip filter
```

Add the input chain to the filter table:

# nft add chain ip filter
 input
 { type filter hook input priority 0 \; }

Add a rule that drops all packets from source addresses that attempt to establish more than ten TCP connections within one minute:
```
# nft add rule ip filter
 input ip protocol tcp ct state new, untracked meter ratemeter
 { ip saddr timeout 5m
 limit rate over 10/minute
 } drop
```
The timeout 5m parameter defines that nftables automatically removes entries after five minutes to prevent that the meter fills up with stale entries.

Verification

To display the meter’s content, enter:

# nft list meter ip filter
 ratemeter
table ip filter {
  meter ratemeter {
    type ipv4_addr
    size 65535
    flags dynamic,timeout
    elements = { 192.0.2.1 limit rate over 10/minute timeout 5m expires 4m58s224ms }
  }
}

47.10. Debugging nftables rules

The nftables framework provides different options for administrators to debug rules and if packets match them.

47.10.1. Creating a rule with a counter

To identify if a rule is matched, you can use a counter.

For more information on a procedure that adds a counter to an existing rule, see Adding a counter to an existing rule.

Prerequisites

The chain to which you want to add the rule exists.

Procedure

Add a new rule with the counter parameter to the chain. The following example adds a rule with a counter that allows TCP traffic on port 22 and counts the packets and traffic that match this rule:
```
# nft add rule inet
 example_table
 example_chain
 tcp
 dport 22
 counter
 accept
```

To display the counter values:

# nft list ruleset
table inet example_table {
  chain example_chain {
    type filter hook input priority filter; policy accept;
    tcp dport ssh counter packets 
6872
 bytes 105448565 accept
  }
}

47.10.2. Adding a counter to an existing rule

To identify if a rule is matched, you can use a counter.

For more information on a procedure that adds a new rule with a counter, see Creating a rule with the counter.

Prerequisites

The rule to which you want to add the counter exists.

Procedure

Display the rules in the chain including their handles:

# nft --handle list chain inet
 example_table
 example_chain
table inet example_table {
  chain example_chain { # handle 1
    type filter hook input priority filter; policy accept;
    tcp dport ssh accept # handle 4
  }
}

Add the counter by replacing the rule but with the counter parameter. The following example replaces the rule displayed in the previous step and adds a counter:
```
# nft replace rule inet
 example_table
 example_chain
 handle 4
 tcp
 dport 22
 counter
 accept
```

To display the counter values:

# nft list ruleset
table inet
 example_table {
  chain example_chain {
    type filter hook input priority filter; policy accept;
    tcp dport ssh counter packets 
6872
 bytes 105448565 accept
  }
}

47.10.3. Monitoring packets that match an existing rule

The tracing feature in nftables in combination with the nft monitor command enables administrators to display packets that match a rule. You can enable tracing for a rule an use it to monitoring packets that match this rule.

Prerequisites

The rule to which you want to add the counter exists.

Procedure

Display the rules in the chain including their handles:

# nft --handle list chain inet
 example_table
 example_chain
table inet example_table {
  chain example_chain { # handle 1
    type filter hook input priority filter; policy accept;
    tcp dport ssh accept # handle 4
  }
}

Add the tracing feature by replacing the rule but with the meta nftrace set 1 parameters. The following example replaces the rule displayed in the previous step and enables tracing:
```
# nft replace rule inet
 example_table
 example_chain
 handle 4
 tcp
 dport 22
 meta nftrace set 1
 accept
```

Use the nft monitor command to display the tracing. The following example filters the output of the command to display only entries that contain inet example_table example_chain:

# nft monitor | grep "inet example_table example_chain"
trace id 3c5eb15e inet example_table example_chain packet: iif "enp1s0" ether saddr 52:54:00:17:ff:e4 ether daddr 52:54:00:72:2f:6e ip saddr 192.0.2.1 ip daddr 192.0.2.2 ip dscp cs0 ip ecn not-ect ip ttl 64 ip id 49710 ip protocol tcp ip length 60 tcp sport 56728 tcp dport ssh tcp flags == syn tcp window 64240
trace id 3c5eb15e inet example_table example_chain rule tcp dport ssh nftrace set 1 accept (verdict accept)
...

Warning

Depending on the number of rules with tracing enabled and the amount of matching traffic, the nft monitor command can display a lot of output. Use grep or other utilities to filter the output.

47.11. Backing up and restoring the nftables rule set

You can backup nftables rules to a file and later restoring them. Also, administrators can use a file with the rules to, for example, transfer the rules to a different server.

47.11.1. Backing up the nftables rule set to a file

You can use the nft utility to back up the nftables rule set to a file.

Procedure

To backup nftables rules:
- In a format produced by nft list ruleset format:
```
# nft list ruleset > file
.nft
```
- In JSON format:
```
# nft -j list ruleset > file
.json
```

47.11.2. Restoring the nftables rule set from a file

You can restore the nftables rule set from a file.

Procedure

To restore nftables rules:
- If the file to restore is in the format produced by nft list ruleset or contains nft commands directly:
```
# nft -f file
.nft
```
- If the file to restore is in JSON format:
```
# nft -j -f file
.json
```

47.12. Additional resources

Using nftables in Red Hat Enterprise Linux 8
What comes after iptables? Its successor, of course: nftables
Firewalld: The Future is nftables

Chapter 48. Using xdp-filter for high-performance traffic filtering to prevent DDoS attacks

Compared to packet filters, such as nftables, Express Data Path (XDP) processes and drops network packets right at the network interface. Therefore, XDP determines the next step for the package before it reaches a firewall or other applications. As a result, XDP filters require less resources and can process network packets at a much higher rate than conventional packet filters to defend against distributed denial of service (DDoS) attacks. For example, during testing, Red Hat dropped 26 million network packets per second on a single core, which is significantly higher than the drop rate of nftables on the same hardware.

The xdp-filter utility allows or drops incoming network packets using XDP. You can create rules to filter traffic to or from specific:

IP addresses
MAC addresses
Ports

Note that, even if xdp-filter has a significantly higher packet-processing rate, it does not have the same capabilities as, for example, nftables. Consider xdp-filter a conceptual utility to demonstrate packet filtering using XDP. Additionally, you can use the code of the utility for a better understanding of how to write your own XDP applications.

Important

On other architectures than AMD and Intel 64-bit, the xdp-filter utility is provided as a Technology Preview only. Technology Preview features are not supported with Red Hat production Service Level Agreements (SLAs), might not be functionally complete, and Red Hat does not recommend using them for production. These previews provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

See Technology Preview Features Support Scope on the Red Hat Customer Portal for information about the support scope for Technology Preview features.

48.1. Dropping network packets that match an xdp-filter rule

You can use xdp-filter to drop network packets:

To a specific destination port
From a specific IP address
From a specific MAC address

The allow policy of xdp-filter defines that all traffic is allowed and the filter drops only network packets that match a particular rule. For example, use this method if you know the source IP addresses of packets you want to drop.

Prerequisites

The xdp-tools package is installed.
A network driver that supports XDP programs.

Procedure

Load xdp-filter to process incoming packets on a certain interface, such as enp1s0:
```
# xdp-filter load enp1s0
```
By default, xdp-filter uses the allow policy, and the utility drops only traffic that matches any rule.

Optionally, use the -f feature option to enable only particular features, such as tcp, ipv4, or ethernet. Loading only the required features instead of all of them increases the speed of packet processing. To enable multiple features, separate them with a comma.

If the command fails with an error, the network driver does not support XDP programs.
Add rules to drop packets that match them. For example:
- To drop incoming packets to port 22, enter:
```
# xdp-filter port 22
```
  This command adds a rule that matches TCP and UDP traffic. To match only a particular protocol, use the -p protocol option.
- To drop incoming packets from 192.0.2.1, enter:
```
# xdp-filter ip 192.0.2.1
 -m src
```
  Note that xdp-filter does not support IP ranges.
- To drop incoming packets from MAC address 00:53:00:AA:07:BE, enter:
```
# xdp-filter ether 00:53:00:AA:07:BE
 -m src
```

Verification steps

Use the following command to display statistics about dropped and allowed packets:
```
# xdp-filter status
```

Additional resources

xdp-filter(8) man page
If you are a developer and interested in the code of xdp-filter, download and install the corresponding source RPM (SRPM) from the Red Hat Customer Portal.

48.2. Dropping all network packets except the ones that match an xdp-filter rule

You can use xdp-filter to allow only network packets:

From and to a specific destination port
From and to a specific IP address
From and to specific MAC address

To do so, use the deny policy of xdp-filter which defines that the filter drops all network packets except the ones that match a particular rule. For example, use this method if you do not know the source IP addresses of packets you want to drop.

Warning

If you set the default policy to deny when you load xdp-filter on an interface, the kernel immediately drops all packets from this interface until you create rules that allow certain traffic. To avoid being locked out from the system, enter the commands locally or connect through a different network interface to the host.

Prerequisites

The xdp-tools package is installed.
You are logged in to the host either locally or using a network interface for which you do not plan to filter the traffic.
A network driver that supports XDP programs.

Procedure

Load xdp-filter to process packets on a certain interface, such as enp1s0:
```
# xdp-filter load enp1s0
 -p deny
```
Optionally, use the -f feature option to enable only particular features, such as tcp, ipv4, or ethernet. Loading only the required features instead of all of them increases the speed of packet processing. To enable multiple features, separate them with a comma.

If the command fails with an error, the network driver does not support XDP programs.
Add rules to allow packets that match them. For example:
- To allow packets to port 22, enter:
```
# xdp-filter port 22
```
  This command adds a rule that matches TCP and UDP traffic. To match only a particular protocol, pass the -p protocol option to the command.
- To allow packets to 192.0.2.1, enter:
```
# xdp-filter ip 192.0.2.1
```
  Note that xdp-filter does not support IP ranges.
- To allow packets to MAC address 00:53:00:AA:07:BE, enter:
```
# xdp-filter ether 00:53:00:AA:07:BE
```
Important

The xdp-filter utility does not support stateful packet inspection. This requires that you either do not set a mode using the -m mode option or you add explicit rules to allow incoming traffic that the machine receives in reply to outgoing traffic.

Verification steps

Use the following command to display statistics about dropped and allowed packets:
```
# xdp-filter status
```

Additional resources

xdp-filter(8) man page.
If you are a developer and you are interested in the code of xdp-filter, download and install the corresponding source RPM (SRPM) from the Red Hat Customer Portal.

Chapter 49. Getting started with DPDK

The data plane development kit (DPDK) provides libraries and network drivers to accelerate packet processing in user space.

Administrators use DPDK, for example, in virtual machines to use Single Root I/O Virtualization (SR-IOV) to reduce latencies and increase I/O throughput.

Note

Red Hat does not support experimental DPDK APIs.

49.1. Installing the dpdk package

To use DPDK, install the dpdk package.

Procedure

Use the yum utility to install the dpdk package:
```
# yum install dpdk
```

49.2. Additional resources

Network Adapter Fast Datapath Feature Support Matrix

Chapter 50. Understanding the eBPF networking features in RHEL 8

The extended Berkeley Packet Filter (eBPF) is an in-kernel virtual machine that allows code execution in the kernel space. This code runs in a restricted sandbox environment with access only to a limited set of functions.

In networking, you can use eBPF to complement or replace kernel packet processing. Depending on the hook you use, eBPF programs have, for example:

Read and write access to packet data and metadata
Can look up sockets and routes
Can set socket options
Can redirect packets

50.1. Overview of networking eBPF features in RHEL 8

You can attach extended Berkeley Packet Filter (eBPF) networking programs to the following hooks in RHEL:

eXpress Data Path (XDP): Provides early access to received packets before the kernel networking stack processes them.
tc eBPF classifier with direct-action flag: Provides powerful packet processing on ingress and egress.
Control Groups version 2 (cgroup v2): Enables filtering and overriding socket-based operations performed by programs in a control group.
Socket filtering: Enables filtering of packets received from sockets. This feature was also available in the classic Berkeley Packet Filter (cBPF), but has been extended to support eBPF programs.
Stream parser: Enables splitting up streams to individual messages, filtering, and redirecting them to sockets.
SO_REUSEPORT socket selection: Provides a programmable selection of a receiving socket from a reuseport socket group.
Flow dissector: Enables overriding the way the kernel parses packet headers in certain situations.
TCP congestion control callbacks: Enables implementing a custom TCP congestion control algorithm.
Routes with encapsulation: Enables creating custom tunnel encapsulation.

Note that Red Hat does not support all of the eBPF functionality that is available in RHEL and described here. For further details and the support status of the individual hooks, see the RHEL 8 Release Notes and the following overview.

XDP

You can attach programs of the BPF_PROG_TYPE_XDP type to a network interface. The kernel then executes the program on received packets before the kernel network stack starts processing them. This allows fast packet forwarding in certain situations, such as fast packet dropping to prevent distributed denial of service (DDoS) attacks and fast packet redirects for load balancing scenarios.

You can also use XDP for different forms of packet monitoring and sampling. The kernel allows XDP programs to modify packets and to pass them for further processing to the kernel network stack.

The following XDP modes are available:

Native (driver) XDP: The kernel executes the program from the earliest possible point during packet reception. At this moment, the kernel did not parse the packet and, therefore, no metadata provided by the kernel is available. This mode requires that the network interface driver supports XDP but not all drivers support this native mode.
Generic XDP: The kernel network stack executes the XDP program early in the processing. At that time, kernel data structures have been allocated, and the packet has been pre-processed. If a packet should be dropped or redirected, it requires a significant overhead compared to the native mode. However, the generic mode does not require network interface driver support and works with all network interfaces.
Offloaded XDP: The kernel executes the XDP program on the network interface instead of on the host CPU. Note that this requires specific hardware, and only certain eBPF features are available in this mode.

On RHEL, load all XDP programs using the libxdp library. This library enables system-controlled usage of XDP.

Note

Currently, there are some system configuration limitations for XDP programs. For example, you must disable certain hardware offload features on the receiving interface. Additionally, not all features are available with all drivers that support the native mode.

In RHEL 8.7, Red Hat supports the XDP feature only if all of the following conditions apply:

You load the XDP program on an AMD or Intel 64-bit architecture.
You use the libxdp library to load the program into the kernel.
The XDP program does not use the XDP hardware offloading.

Additionally, Red Hat provides the following usage of XDP features as unsupported Technology Preview:

Loading XDP programs on architectures other than AMD and Intel 64-bit. Note that the libxdp library is not available for architectures other than AMD and Intel 64-bit.
The XDP hardware offloading.

AF_XDP

Using an XDP program that filters and redirects packets to a given AF_XDP socket, you can use one or more sockets from the AF_XDP protocol family to quickly copy packets from the kernel to the user space.

In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.

Traffic Control

The Traffic Control (tc) subsystem offers the following types of eBPF programs:

BPF_PROG_TYPE_SCHED_CLS
BPF_PROG_TYPE_SCHED_ACT

These types enable you to write custom tc classifiers and tc actions in eBPF. Together with the parts of the tc ecosystem, this provides the ability for powerful packet processing and is the core part of several container networking orchestration solutions.

In most cases, only the classifier is used, as with the direct-action flag, the eBPF classifier can execute actions directly from the same eBPF program. The clsact Queueing Discipline (qdisc) has been designed to enable this on the ingress side.

Note that using a flow dissector eBPF program can influence operation of some other qdiscs and tc classifiers, such as flower.

The eBPF for tc feature is fully supported in RHEL 8.2 and later.

Socket filter

Several utilities use or have used the classic Berkeley Packet Filter (cBPF) for filtering packets received on a socket. For example, the tcpdump utility enables the user to specify expressions, which tcpdump then translates into cBPF code.

As an alternative to cBPF, the kernel allows eBPF programs of the BPF_PROG_TYPE_SOCKET_FILTER type for the same purpose.

In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.

Control Groups

In RHEL, you can use multiple types of eBPF programs that you can attach to a cgroup. The kernel executes these programs when a program in the given cgroup performs an operation. Note that you can use only cgroups version 2.

The following networking-related cgroup eBPF programs are available in RHEL:

BPF_PROG_TYPE_SOCK_OPS: The kernel calls this program on various TCP events. The program can adjust the behavior of the kernel TCP stack, including custom TCP header options, and so on.
BPF_PROG_TYPE_CGROUP_SOCK_ADDR: The kernel calls this program during connect, bind, sendto, recvmsg, getpeername, and getsockname operations. This program allows changing IP addresses and ports. This is useful when you implement socket-based network address translation (NAT) in eBPF.
BPF_PROG_TYPE_CGROUP_SOCKOPT: The kernel calls this program during setsockopt and getsockopt operations and allows changing the options.
BPF_PROG_TYPE_CGROUP_SOCK: The kernel calls this program during socket creation, socket releasing, and binding to addresses. You can use these programs to allow or deny the operation, or only to inspect socket creation for statistics.
BPF_PROG_TYPE_CGROUP_SKB: This program filters individual packets on ingress and egress, and can accept or reject packets.
BPF_PROG_TYPE_CGROUP_SYSCTL: This program allows filtering of access to system controls (sysctl).
BPF_CGROUP_INET4_GETPEERNAME, BPF_CGROUP_INET6_GETPEERNAME, BPF_CGROUP_INET4_GETSOCKNAME, and BPF_CGROUP_INET6_GETSOCKNAME: Using these programs, you can override the result of getsockname and getpeername system calls. This is useful when you implement socket-based network address translation (NAT) in eBPF.

In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.

Stream Parser

A stream parser operates on a group of sockets that are added to a special eBPF map. The eBPF program then processes packets that the kernel receives or sends on those sockets.

The following stream parser eBPF programs are available in RHEL:

BPF_PROG_TYPE_SK_SKB: An eBPF program parses packets received from the socket into individual messages, and instructs the kernel to drop those messages or send them to another socket in the group.
BPF_PROG_TYPE_SK_MSG: This program filters egress messages. An eBPF program parses the packets into individual messages and either approves or rejects them.

In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.

SO_REUSEPORT socket selection

Using this socket option, you can bind multiple sockets to the same IP address and port. Without eBPF, the kernel selects the receiving socket based on a connection hash. With the BPF_PROG_TYPE_SK_REUSEPORT program, the selection of the receiving socket is fully programmable.

In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.

Flow dissector

When the kernel needs to process packet headers without going through the full protocol decode, they are dissected. For example, this happens in the tc subsystem, in multipath routing, in bonding, or when calculating a packet hash. In this situation the kernel parses the packet headers and fills internal structures with the information from the packet headers. You can replace this internal parsing using the BPF_PROG_TYPE_FLOW_DISSECTOR program. Note that you can only dissect TCP and UDP over IPv4 and IPv6 in eBPF in RHEL.

In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.

TCP Congestion Control

You can write a custom TCP congestion control algorithm using a group of BPF_PROG_TYPE_STRUCT_OPS programs that implement struct tcp_congestion_oops callbacks. An algorithm that is implemented this way is available to the system alongside the built-in kernel algorithms.

In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.

Routes with encapsulation

You can attach one of the following eBPF program types to routes in the routing table as a tunnel encapsulation attribute:

BPF_PROG_TYPE_LWT_IN
BPF_PROG_TYPE_LWT_OUT
BPF_PROG_TYPE_LWT_XMIT

The functionality of such an eBPF program is limited to specific tunnel configurations and does not allow creating a generic encapsulation or decapsulation solution.

In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.

Socket lookup

To bypass limitations of the bind system call, use an eBPF program of the BPF_PROG_TYPE_SK_LOOKUP type. Such programs can select a listening socket for new incoming TCP connections or an unconnected socket for UDP packets.

In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.

50.2. Overview of XDP features in RHEL 8 by network cards

The following is an overview of XDP-enabled network cards and the XDP features you can use with them:

Network cardDriverBasicRedirectTargetHW offloadZero-copy

Amazon Elastic Network Adapter

ena

yes

Broadcom NetXtreme-C/E 10/25/40/50 gigabit Ethernet

bnxt_en

yes

Cavium Thunder Virtual function

nicvf

yes

Intel® 10GbE PCI Express Virtual Function Ethernet

ixgbevf

yes

Intel® 10GbE PCI Express adapters

ixgbe

yes

Intel® Ethernet Connection E800 Series

ice

yes

Intel® Ethernet Controller I225-LM/I225-V family

igc

yes

Intel® Ethernet Controller XL710 Family

i40e

yes

Intel® PCI Express Gigabit adapters

igb

yes

Mellanox 5th generation network adapters (ConnectX series)

mlx5_core

yes

Mellanox Technologies 1/10/40Gbit Ethernet

mlx4_en

yes

Microsoft Azure Network Adapter

mana

yes

Microsoft Hyper-V virtual network

hv_netvsc

yes

Netronome® NFP4000/NFP6000 NIC

nfp

yes

QEMU Virtio network

virtio_net

yes

QLogic QED 25/40/100Gb Ethernet NIC

qede

yes

Solarflare SFC9000/SFC9100/EF100-family

sfc

yes

Universal TUN/TAP device

tun

yes

Virtual Ethernet pair device

veth

yes

Legend:

Basic: Supports basic return codes: DROP, PASS, ABORTED, and TX.
Redirect: Supports the REDIRECT return code.
Target: Can be a target of a REDIRECT return code.
HW offload: Supports XDP hardware offload.
Zero-copy: Supports the zero-copy mode for the AF_XDP protocol family.

Chapter 51. Network tracing using the BPF compiler collection

BPF Compiler Collection (BCC) is a library, which facilitates the creation of the extended Berkeley Packet Filter (eBPF) programs. The main utility of eBPF programs is analyzing the operating system performance and network performance without experiencing overhead or security issues.

BCC removes the need for users to know deep technical details of eBPF, and provides many out-of-the-box starting points, such as the bcc-tools package with pre-created eBPF programs.

Note

The eBPF programs are triggered on events, such as disk I/O, TCP connections, and process creations. It is unlikely that the programs should cause the kernel to crash, loop or become unresponsive because they run in a safe virtual machine in the kernel.

51.2. Displaying TCP connections added to the Kernel’s accept queue

After the kernel receives the ACK packet in a TCP 3-way handshake, the kernel moves the connection from the SYN queue to the accept queue after the connection’s state changes to ESTABLISHED. Therefore, only successful TCP connections are visible in this queue.

The tcpaccept utility uses eBPF features to display all connections the kernel adds to the accept queue. The utility is lightweight because it traces the accept() function of the kernel instead of capturing packets and filtering them. For example, use tcpaccept for general troubleshooting to display new connections the server has accepted.

Procedure

Enter the following command to start the tracing the kernel accept queue:

/usr/share/bcc/tools/tcpaccept

PID COMM IP RADDR RPORT LADDR LPORT 843 sshd 4 192.0.2.17 50598 192.0.2.1 22 1107 ns-slapd 4 198.51.100.6 38772 192.0.2.1 389 1107 ns-slapd 4 203.0.113.85 38774 192.0.2.1 389 ...

Each time the kernel accepts a connection, tcpaccept displays the details of the connections.

Press

Ctrl

+

C

to stop the tracing process.

Additional resources

tcpaccept(8) man page
/usr/share/bcc/tools/doc/tcpaccept_example.txt file

51.3. Tracing outgoing TCP connection attempts

The tcpconnect utility uses eBPF features to trace outgoing TCP connection attempts. The output of the utility also includes connections that failed.

The tcpconnect utility is lightweight because it traces, for example, the connect() function of the kernel instead of capturing packets and filtering them.

Procedure

Enter the following command to start the tracing process that displays all outgoing connections:

/usr/share/bcc/tools/tcpconnect

PID COMM IP SADDR DADDR DPORT 31346 curl 4 192.0.2.1 198.51.100.16 80 31348 telnet 4 192.0.2.1 203.0.113.231 23 31361 isc-worker00 4 192.0.2.1 192.0.2.254 53 ...

Each time the kernel processes an outgoing connection, tcpconnect displays the details of the connections.

Press

Ctrl

+

C

to stop the tracing process.

Additional resources

tcpconnect(8) man page
/usr/share/bcc/tools/doc/tcpconnect_example.txt file

51.4. Measuring the latency of outgoing TCP connections

The TCP connection latency is the time taken to establish a connection. This typically involves the kernel TCP/IP processing and network round trip time, and not the application runtime.

The tcpconnlat utility uses eBPF features to measure the time between a sent SYN packet and the received response packet.

Procedure

Start measuring the latency of outgoing connections:

/usr/share/bcc/tools/tcpconnlat

PID COMM IP SADDR DADDR DPORT LAT(ms) 32151 isc-worker00 4 192.0.2.1 192.0.2.254 53 0.60 32155 ssh 4 192.0.2.1 203.0.113.190 22 26.34 32319 curl 4 192.0.2.1 198.51.100.59 443 188.96 ...

Each time the kernel processes an outgoing connection, tcpconnlat displays the details of the connection after the kernel receives the response packet.

Press

Ctrl

+

C

to stop the tracing process.

Additional resources

tcpconnlat(8) man page
/usr/share/bcc/tools/doc/tcpconnlat_example.txt file

51.5. Displaying details about TCP packets and segments that were dropped by the kernel

The tcpdrop utility enables administrators to display details about TCP packets and segments that were dropped by the kernel. Use this utility to debug high rates of dropped packets that can cause the remote system to send timer-based retransmits. High rates of dropped packets and segments can impact the performance of a server.

Instead of capturing and filtering packets, which is resource-intensive, the tcpdrop utility uses eBPF features to retrieve the information directly from the kernel.

Procedure

Enter the following command to start displaying details about dropped TCP packets and segments:

# /usr/share/bcc/tools/tcpdrop
TIME     PID    IP SADDR:SPORT       > DADDR:DPORT   STATE (FLAGS)
13:28:39 32253  4  192.0.2.85:51616  > 192.0.2.1:22  CLOSE_WAIT (FIN|ACK)
	b'tcp_drop+0x1'
	b'tcp_data_queue+0x2b9'
	...

13:28:39 1      4  192.0.2.85:51616  > 192.0.2.1:22   CLOSE (ACK)
	b'tcp_drop+0x1'
	b'tcp_rcv_state_process+0xe2'
	...

Each time the kernel drops TCP packets and segments, tcpdrop displays the details of the connection, including the kernel stack trace that led to the dropped package.

Press

Ctrl

+

C

to stop the tracing process.

Additional resources

tcpdrop(8) man page
/usr/share/bcc/tools/doc/tcpdrop_example.txt file

51.6. Tracing TCP sessions

The tcplife utility uses eBPF to trace TCP sessions that open and close, and prints a line of output to summarize each one. Administrators can use tcplife to identify connections and the amount of transferred traffic.

For example, you can display connections to port 22 (SSH) to retrieve the following information:

The local process ID (PID)
The local process name
The local IP address and port number
The remote IP address and port number
The amount of received and transmitted traffic in KB.
The time in milliseconds the connection was active

Procedure

Enter the following command to start the tracing of connections to the local port 22:

/usr/share/bcc/tools/tcplife -L 22
PID   COMM    LADDR      LPORT RADDR       RPORT TX_KB  RX_KB      MS
19392 sshd    192.0.2.1  22    192.0.2.17  43892    53     52 6681.95
19431 sshd    192.0.2.1  22    192.0.2.245 43902    81 249381 7585.09
19487 sshd    192.0.2.1  22    192.0.2.121 43970  6998     7 16740.35
...

Each time a connection is closed, tcplife displays the details of the connections.

Press

Ctrl

+

C

to stop the tracing process.

Additional resources

tcplife(8) man page
/usr/share/bcc/tools/doc/tcplife_example.txt file

51.7. Tracing TCP retransmissions

The tcpretrans utility displays details about TCP retransmissions, such as the local and remote IP address and port number, as well as the TCP state at the time of the retransmissions.

The utility uses eBPF features and, therefore, has a very low overhead.

Procedure

Use the following command to start displaying TCP retransmission details:

/usr/share/bcc/tools/tcpretrans

TIME PID IP LADDR:LPORT T> RADDR:RPORT STATE 00:23:02 0 4 192.0.2.1:22 R> 198.51.100.0:26788 ESTABLISHED 00:23:02 0 4 192.0.2.1:22 R> 198.51.100.0:26788 ESTABLISHED 00:45:43 0 4 192.0.2.1:22 R> 198.51.100.0:17634 ESTABLISHED ...

Each time the kernel calls the TCP retransmit function, tcpretrans displays the details of the connection.

Press

Ctrl

+

C

to stop the tracing process.

Additional resources

tcpretrans(8) man page
/usr/share/bcc/tools/doc/tcpretrans_example.txt file

51.8. Displaying TCP state change information

During a TCP session, the TCP state changes. The tcpstates utility uses eBPF functions to trace these state changes, and prints details including the duration in each state. For example, use tcpstates to identify if connections spend too much time in the initialization state.

Procedure

Use the following command to start tracing TCP state changes:

/usr/share/bcc/tools/tcpstates

SKADDR C-PID C-COMM LADDR LPORT RADDR RPORT OLDSTATE -> NEWSTATE MS ffff9cd377b3af80 0 swapper/1 0.0.0.0 22 0.0.0.0 0 LISTEN -> SYN_RECV 0.000 ffff9cd377b3af80 0 swapper/1 192.0.2.1 22 192.0.2.45 53152 SYN_RECV -> ESTABLISHED 0.067 ffff9cd377b3af80 818 sssd_nss 192.0.2.1 22 192.0.2.45 53152 ESTABLISHED -> CLOSE_WAIT 65636.773 ffff9cd377b3af80 1432 sshd 192.0.2.1 22 192.0.2.45 53152 CLOSE_WAIT -> LAST_ACK 24.409 ffff9cd377b3af80 1267 pulseaudio 192.0.2.1 22 192.0.2.45 53152 LAST_ACK -> CLOSE 0.376 ...

Each time a connection changes its state, tcpstates displays a new line with updated connection details.

If multiple connections change their state at the same time, use the socket address in the first column (SKADDR) to determine which entries belong to the same connection.

Press

Ctrl

+

C

to stop the tracing process.

Additional resources

tcpstates(8) man page
/usr/share/bcc/tools/doc/tcpstates_example.txt file

51.9. Summarizing and aggregating TCP traffic sent to specific subnets

The tcpsubnet utility summarizes and aggregates IPv4 TCP traffic that the local host sends to subnets and displays the output on a fixed interval. The utility uses eBPF features to collect and summarize the data to reduce the overhead.

By default, tcpsubnet summarizes traffic for the following subnets:

127.0.0.1/32
10.0.0.0/8
172.16.0.0/12
192.0.2.0/24/16
0.0.0.0/0

Note that the last subnet (0.0.0.0/0) is a catch-all option. The tcpsubnet utility counts all traffic for subnets different than the first four in this catch-all entry.

Follow the procedure to count the traffic for the 192.0.2.0/24 and 198.51.100.0/24 subnets. Traffic to other subnets will be tracked in the 0.0.0.0/0 catch-all subnet entry.

Procedure

Start monitoring the amount of traffic send to the 192.0.2.0/24, 198.51.100.0/24, and other subnets:

/usr/share/bcc/tools/tcpsubnet 192.0.2.0/24,198.51.100.0/24,0.0.0.0/0

Tracing... Output every 1 secs. Hit Ctrl-C to end [02/21/20 10:04:50] 192.0.2.0/24 856 198.51.100.0/24 7467 [02/21/20 10:04:51] 192.0.2.0/24 1200 198.51.100.0/24 8763 0.0.0.0/0 673 ...

This command displays the traffic in bytes for the specified subnets once per second.

Press

Ctrl

+

C

to stop the tracing process.

Additional resources

tcpsubnet(8) man page
/usr/share/bcc/tools/doc/tcpsubnet.txt file

51.10. Displaying the network throughput by IP address and port

The tcptop utility displays TCP traffic the host sends and receives in kilobytes. The report automatically refreshes and contains only active TCP connections. The utility uses eBPF features and, therefore, has only a very low overhead.

Procedure

To monitor the sent and received traffic, enter:

/usr/share/bcc/tools/tcptop

13:46:29 loadavg: 0.10 0.03 0.01 1/215 3875 PID COMM LADDR RADDR RX_KB TX_KB 3853 3853 192.0.2.1:22 192.0.2.165:41838 32 102626 1285 sshd 192.0.2.1:22 192.0.2.45:39240 0 0 ...

The output of the command includes only active TCP connections. If the local or remote system closes a connection, the connection is no longer visible in the output.

Press

Ctrl

+

C

to stop the tracing process.

Additional resources

tcptop(8) man page
/usr/share/bcc/tools/doc/tcptop.txt file

51.11. Tracing established TCP connections

The tcptracer utility traces the kernel functions that connect, accept, and close TCP connections. The utility uses eBPF features and, therefore, has a very low overhead.

Procedure

Use the following command to start the tracing process:

/usr/share/bcc/tools/tcptracer

Tracing TCP established connections. Ctrl-C to end. T PID COMM IP SADDR DADDR SPORT DPORT A 1088 ns-slapd 4 192.0.2.153 192.0.2.1 0 65535 A 845 sshd 4 192.0.2.1 192.0.2.67 22 42302 X 4502 sshd 4 192.0.2.1 192.0.2.67 22 42302 ...

Each time the kernel connects, accepts, or closes a connection, tcptracer displays the details of the connections.

Press

Ctrl

+

C

to stop the tracing process.

Additional resources

tcptracer(8) man page
/usr/share/bcc/tools/doc/tcptracer_example.txt file

51.12. Tracing IPv4 and IPv6 listen attempts

The solisten utility traces all IPv4 and IPv6 listen attempts. It traces the listen attempts including that ultimately fail or the listening program that does not accept the connection. The utility traces function that the kernel calls when a program wants to listen for TCP connections.

Procedure

Enter the following command to start the tracing process that displays all listen TCP attempts:

/usr/share/bcc/tools/solisten

PID COMM PROTO BACKLOG PORT ADDR 3643 nc TCPv4 1 4242 0.0.0.0 3659 nc TCPv6 1 4242 2001:db8:1::1 4221 redis-server TCPv6 128 6379 :: 4221 redis-server TCPv4 128 6379 0.0.0.0 ....

Press

Ctrl

+

C

to stop the tracing process.

Additional resources

solisten(9) man page
/usr/share/bcc/tools/doc/solisten_example.txt file

51.13. Summarizing the service time of soft interrupts

The softirqs utility summarizes the time spent servicing soft interrupts (soft IRQs) and shows this time as either totals or histogram distributions. This utility uses the irq:softirq_enter and irq:softirq_exit kernel tracepoints, which is a stable tracing mechanism.

Procedure

Enter the following command to start the tracing soft irq event time:

/usr/share/bcc/tools/softirqs

Tracing soft irq event time... Hit Ctrl-C to end. ^C SOFTIRQ TOTAL_usecs tasklet 166 block 9152 net_rx 12829 rcu 53140 sched 182360 timer 306256

Press

Ctrl

+

C

to stop the tracing process.

Additional resources

softirqs(8) man page
/usr/share/bcc/tools/doc/softirqs_example.txt file
mpstat(1) man page

51.14. Additional resources

/usr/share/doc/bcc/README.md file

Chapter 52. Getting started with TIPC

Transparent Inter-process Communication (TIPC), which is also known as Cluster Domain Sockets, is an Inter-process Communication (IPC) service for cluster-wide operation.

Applications that are running in a high-available and dynamic cluster environment have special needs. The number of nodes in a cluster can vary, routers can fail, and, due to load balancing considerations, functionality can be moved to different nodes in the cluster. TIPC minimizes the effort by application developers to deal with such situations, and maximizes the chance that they are handled in a correct and optimal way. Additionally, TIPC provides a more efficient and fault-tolerant communication than general protocols, such as TCP.

52.1. The architecture of TIPC

TIPC is a layer between applications using TIPC and a packet transport service (bearer), and spans the level of transport, network, and signaling link layers. However, TIPC can use a different transport protocol as bearer, so that, for example, a TCP connection can serve as a bearer for a TIPC signaling link.

TIPC supports the following bearers:

Ethernet
InfiniBand
UDP protocol

TIPC provides a reliable transfer of messages between TIPC ports, that are the endpoints of all TIPC communication.

The following is a diagram of the TIPC architecture:

52.2. Loading the tipc module when the system boots

Before you can use the TIPC protocol, you must load the tipc kernel module. You can configure Red Hat Enterprise Linux to automatically load this kernel module automatically when the system boots.

Procedure

Create the /etc/modules-load.d/tipc.conf file with the following content:
```
tipc
```
Restart the systemd-modules-load service to load the module without rebooting the system:
```
# systemctl start systemd-modules-load
```

Verification steps

Use the following command to verify that RHEL loaded the tipc module:
```
# lsmod | grep tipc
tipc    311296
  0
```
If the command shows no entry for the tipc module, RHEL failed to load it.

Additional resources

modules-load.d(5) man page

52.3. Creating a TIPC network

To create a TIPC network, perform this procedure on each host that should join the TIPC network.

Important

The commands configure the TIPC network only temporarily. To permanently configure TIPC on a node, use the commands of this procedure in a script, and configure RHEL to execute that script when the system boots.

Prerequisites

The tipc module has been loaded. For details, see Loading the tipc module when the system boots

Procedure

Optional: Set a unique node identity, such as a UUID or the node’s host name:
```
# tipc node set identity 
host_name
```
The identity can be any unique string consisting of a maximum 16 letters and numbers.

You cannot set or change an identity after this step.
Add a bearer. For example, to use Ethernet as media and enp0s1 device as physical bearer device, enter:
```
# tipc bearer enable media 
eth
 device enp1s0
```
Optional: For redundancy and better performance, attach further bearers using the command from the previous step. You can configure up to three bearers, but not more than two on the same media.
Repeat all previous steps on each node that should join the TIPC network.

Verification steps

Display the link status for cluster members:
```
# tipc link list
broadcast-link: up
5254006b74be:enp1s0-525400df55d1:enp1s0: up
```
This output indicates that the link between bearer enp1s0 on node 5254006b74be and bearer enp1s0 on node 525400df55d1 is up.
Display the TIPC publishing table:
```
# tipc nametable show
Type       Lower      Upper      Scope    Port       Node
0          1795222054 1795222054 cluster  0          5254006b74be
0          3741353223 3741353223 cluster  0          525400df55d1
1          1          1          node     2399405586 5254006b74be
2          3741353223 3741353223 node     0          5254006b74be
```
- The two entries with service type 0 indicate that two nodes are members of this cluster.
- The entry with service type 1 represents the built-in topology service tracking service.
- The entry with service type 2 displays the link as seen from the issuing node. The range limit 3741353223 represents peer endpoint’s address (a unique 32-bit hash value based on the node identity) in decimal format.

Additional resources

tipc-bearer(8) man page
tipc-namespace(8) man page

52.4. Additional resources

Red Hat recommends to use other bearer level protocols to encrypt the communication between nodes based on the transport media. For example:
- MACSec: See Using MACsec to encrypt layer 2 traffic
- IPsec: See Configuring a VPN with IPsec
For examples of how to use TIPC, clone the upstream GIT repository using the git clone git://git.code.sf.net/p/tipc/tipcutils command. This repository contains the source code of demos and test programs that use TIPC features. Note that this repository is not provided by Red Hat.
/usr/share/doc/kernel-doc- <kernel_version>
/Documentation/output/networking/tipc.html provided by the kernel-doc package.

Chapter 53. Automatically configuring network interfaces in public clouds using nm-cloud-setup

Normally, a virtual machine (VM) has only one interface that is configurable by DHCP. However, some VMs might have multiple network interfaces, IP addresses, and IP subnets on one interface that is not configurable by DHCP. Also, administrators can reconfigure the network while the machine is running. The nm-cloud-setup utility automatically retrieves configuration information from the metadata server of the cloud service provider and updates the network configurations of VM in public clouds.

53.1. Configuring and pre-deploying nm-cloud-setup

To enable and configure network interfaces in public clouds, run nm-cloud-setup as a timer and service.

Note

On Red Hat Enterprise Linux On Demand and AWS golden images, nm-cloud-setup is already enabled and no action is required.

Prerequisite

A network connection exists.
The connection uses DHCP.

By default, NetworkManager creates a connection profile which uses DHCP. If no profile was created because you set the no-auto-default parameter in /etc/NetworkManager/NetworkManager.conf, create this initial connection manually.

Procedure

Install the nm-cloud-setup package:

yum install NetworkManager-cloud-setup

Create and run the snap-in file for the nm-cloud-setup service:
1. Use the following command to start editing the snap-in file:
```
# systemctl edit nm-cloud-setup.service
```
  It is important to either start the service explicitly or reboot the system to make configuration settings effective.
2. Use the systemd snap-in file to configure the cloud provider in nm-cloud-setup. For example, to use Amazon EC2, enter:
```
[Service]
Environment=NM_CLOUD_SETUP_EC2=yes
```
  You can set the following environment variables to enable the cloud provide you use:
  - NM_CLOUD_SETUP_AZURE for Microsoft Azure
  - NM_CLOUD_SETUP_EC2 for Amazon EC2 (AWS)
  - NM_CLOUD_SETUP_GCP for Google Cloud Platform(GCP)
  - NM_CLOUD_SETUP_ALIYUN for Alibaba Cloud (Aliyun)
3. Save the file and quit the editor.
Reload the systemd configuration:
```
# systemctl daemon-reload
```

Enable and start the nm-cloud-setup service:

systemctl enable --now nm-cloud-setup.service

Enable and start the nm-cloud-setup timer:

systemctl enable --now nm-cloud-setup.timer

Additional resources

nm-cloud-setup(8) man page
Configuring an Ethernet connection

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Configuring and managing networking Red Hat Enterprise Linux 8 | Red Hat Customer Portal

Configuring and managing networking

Managing network interfaces, firewalls, and advanced networking features

Making open source more inclusive

Providing feedback on Red Hat documentation

Chapter 1. Consistent network interface device naming

1.1. Network interface device naming hierarchy

1.2. How the network device renaming works

1.3. Predictable network interface device names on the x86_64 platform explained

1.4. Predictable network interface device names on the System z platform explained

1.5. Customizing the prefix of Ethernet interfaces during the installation

1.6. Assigning user-defined network interface names using udev rules

1.7. Assigning user-defined network interface names using systemd link files

Chapter 2. Configuring an Ethernet connection

2.1. Configuring a static Ethernet connection using nmcli

2.2. Configuring a static Ethernet connection using the nmcli interactive editor

2.3. Configuring a static Ethernet connection using nmtui

2.4. Configuring a static Ethernet connection using nmstatectl

2.5. Configuring a static Ethernet connection using RHEL System Roles with the interface name

2.6. Configuring a static Ethernet connection using RHEL System Roles with a device path

2.7. Configuring a dynamic Ethernet connection using nmcli

2.8. Configuring a dynamic Ethernet connection using the nmcli interactive editor

2.9. Configuring a dynamic Ethernet connection using nmtui

2.10. Configuring a dynamic Ethernet connection using nmstatectl

2.11. Configuring a dynamic Ethernet connection using RHEL System Roles with the interface name

2.12. Configuring a dynamic Ethernet connection using RHEL System Roles with a device path

2.13. Configuring an Ethernet connection using control-center

2.14. Configuring an Ethernet connection using nm-connection-editor

2.15. Changing the DHCP client of NetworkManager

2.16. Configuring the DHCP behavior of a NetworkManager connection

2.17. Configuring multiple Ethernet interfaces using a single connection profile by interface name

2.18. Configuring a single connection profile for multiple Ethernet interfaces using PCI IDs

Chapter 3. Managing wifi connections

3.1. Supported wifi security types

3.2. Connecting to a WPA2 or WPA3 Personal-protected wifi network using nmcli commands

3.3. Configuring a wifi connection using nmtui

3.4. Connecting to a wifi network using the GNOME system menu

3.5. Connecting to a wifi network using the GNOME settings application

3.6. Configuring a wifi connection using nm-connection-editor

3.7. Configuring a wifi connection with 802.1X network authentication using the RHEL System Roles

3.8. Configuring 802.1X network authentication on an existing wifi connection using nmcli

3.9. Manually setting the wireless regulatory domain

Chapter 4. Configuring RHEL as a wifi access point

4.1. Identifying whether a wifi device supports the access point mode

4.2. Configuring RHEL as a WPA2 or WPA3 Personal access point

Chapter 5. Configuring VLAN tagging

5.1. Configuring VLAN tagging using nmcli commands

5.2. Configuring VLAN tagging using the RHEL web console

5.3. Configuring VLAN tagging using nmtui

5.4. Configuring VLAN tagging using nm-connection-editor

5.5. Configuring VLAN tagging using nmstatectl

5.6. Configuring VLAN tagging using RHEL System Roles

5.7. Additional resources

Chapter 6. Using a VXLAN to create a virtual layer-2 domain for VMs

6.1. Benefits of VXLANs

6.2. Configuring the Ethernet interface on the hosts

6.3. Creating a network bridge with a VXLAN attached

6.4. Creating a virtual network in libvirt with an existing bridge

6.5. Configuring virtual machines to use VXLAN

Chapter 7. Configuring a network bridge

7.1. Configuring a network bridge using nmcli commands

7.2. Configuring a network bridge using the RHEL web console

7.3. Configuring a network bridge using nmtui

7.4. Configuring a network bridge using nm-connection-editor

7.5. Configuring a network bridge using nmstatectl

7.6. Configuring a network bridge using RHEL System Roles

Chapter 9. Configuring network bonding

9.1. Understanding network bonding

9.2. Understanding the default behavior of controller and port interfaces

9.3. Comparison of network teaming and bonding features

9.4. Upstream Switch Configuration Depending on the Bonding Modes

9.5. Configuring a network bond using nmcli commands

9.6. Configuring a network bond using the RHEL web console

9.7. Configuring a network bond using nmtui

9.8. Configuring a network bond using nm-connection-editor

9.9. Configuring a network bond using nmstatectl

9.10. Configuring a network bond using RHEL System Roles

9.11. Creating a network bond to enable switching between an Ethernet and wireless connection without interrupting the VPN

9.12. The different network bonding modes

9.13. The xmit_hash_policy bonding parameter