What is SFP Port? Everything You Need to Know - Optcore - EU-Vietnam Business Network (EVBN)

An SFP port is a physically small-size slot in a networking device that accepts an SFP module insert. Generally, most modern networking devices have two or more built-in SFP ports, such as Ethernet switches, servers, routers, network interface cards, and fiber media converters. With the port equipped, you may connect different switches via SFP modules and corresponding cables. As a result, it helps you achieve greater bandwidth and higher network throughput.

In this guide, we’ll cover the following:

Mục Lục

What types of SFP ports are there?

Based on the different functions, we can divide them into two types.

SFP combo port

It is simply a compound physical opening that shares the same switch fabric and port number along with the corresponding Ethernet port. In other words, it functions the same as another physical port (primarily as a 1000BASE-T RJ45 port). Since those two ports were compounded, we can not use the two ports simultaneously.

For example, if the SFP combo port is activated, the related RJ45 port is automatically disabled. Because of this principle, we called those ports combo ports.

Now let us look at the real combo port on a switch.

Figure 1: MikroTik 28-Port 10G Ethernet switch port note, image source

SFP uplink port

Before talking about this word, we need to know the uplink port definition. Lifewire explains it like this:

An uplink in computer networking refers to a wired or wireless connection from a local area network (LAN) to a wide area network (WAN). An uplink port on a home router is a special kind of port used to connect to a broadband modem (which is a LAN), and ultimately to the internet (which is a WAN).

Now let’s turn back to discuss the SFP uplink port.

Also called an SFP uplink port, an SFP uplink port usually connects with the downlink port of higher-speed switches. In this scenario, it is acted as the lower-tier network, while another connected device serves as the higher network layer.

For example, we could connect the uplink port of the Lan switch to the downlink port of the higher-speed WAN switch. Of curse, remember they must go via the transceiver module and fiber patch cable.

To avoid any possible error, you should NOT try to connect two uplink ports. Because it will cause a failed link, remember to carefully check the port type before merging with other devices.

However, We can classify them as more different types based on the speed supported.

1G Port: also referred to as gigabit port, supports 1.25G or 1G SFP module; it is the most common transceiver type in the Ethernet switch and router
2G Port: support 2G or 2.5G SFP module. It is an unpopular type, mainly for the 2G FC or SDH/SONET devices
4G Port: support 4G SFP module. It is usually used in fiber channel SAN switches or servers.
8G Port: support 8G SFP+ module. Like a 4G port, it is commonly found in SAN switches or servers.
10G Port: also called 10G SFP+ port, is an enhanced port that supports higher speed. It is suitable for a 10G SFP+ transceiver, providing 10x bandwidth than the regular SFP module.
Multi-rate port: unlike the fixed data rate port, this port supports multi-rate SFP modules. Some 10G Ethernet switches from the top brand feature this port, allowing the network administrator to use multiple speed transceivers in the same ports. It helps to build a flexible and scalable network.

Why is the SFP port important?

Nearly all high-speed network switches will only work with fiber ports, because only fiber can provide the maximum bandwidth over a long distance. Though copper cables yet support high-speed transmission, they are thicker and more expensive, more badly, only suitable for very short lengths.

So, the fiber port is an essential part of modern Ethernet switches. They acted as an important bridge to connect the transceiver and switches. Then transmit the signal to even hundreds of kilometers over the fiber cable.

Now let’s turn to the reason for its importance.

First, since the SFP form factor is the most popular and thriving in the transceiver industry, the SFP form is the most reasonable and cost-effective choice.
Second, SFP is more miniature than GBIC port. Hence, sometimes we also referred it as a mini-GBIC port. That helps double the port density in the same switch space.
Third, it is hot-pluggable. The network administrator can quickly replace the appropriate SFP module without shutting the switches. That makes it perfect for expanding or modifying existing networks without completely changing the cable infrastructure.
Finally, it is cost-effective. Because of the popularity of the SFP form factor, there are so many vendors and choices on the market. Hence, switch manufacturers can easily find a reliable supplier at low prices. And those costs finally react to the switch device pricing, furthermore expanding the networking market.

SFP port vs. SFP+ port vs. XFP port vs. QSFP28 port, what is the difference?

If you are a new man to the networking industry, you may also hear about other related words, such as SFP+ port, XFP port, and QSFP28 port.

Now let’s take a simple look at those words.

SFP port is the most common way to call. However, we may also refer to the SFP high-speed port as an SFP+ port, such as 8G, 10G, and 16G data rates.

Figure 2: MikroTik 100G Ethernet switch port note, image source

XFP port is a physical slot that accepts XFP module plug-ins. It is only for 8G and 10G XFP transceivers but doesn’t support other speeds.

QSFP28 port is primarily for a much higher speed of 100G. Unlike the SFP port, it not only supports a higher-speed transceiver, but also features a bigger size and more pins on the connector.

In a word, SFP and SFP+ port have the same size and refers to the same thing except for the support speed. The QSFP28 port is of different types and is suitable for 100G data center switches.

Below table list the comparison between them.

ComparisonSFP PortSFP+ PortXFP PortQSFP28 PortReachmax 180kmmax 100kmmax 100kmmax 80kmData Rate155M, 622M, 1G, 2G, 4G8G, 10G, 16G8G, 10G100G, 112GPower ConsumptionLowestLowMediumHighPriceLowestMediumMediumHighSizeSmallSmallA bit BiggerA bit BiggerApplicationAccess SwitchesCampus SwitchesCampus SwitchesData center switchTable 1: SFP, SFP+, XFP, QSFP28 port difference

FAQ

What is the maximum link distance between two SFP ports?

It depends on the SFP module and fiber cable. Different optical modules and fiber optic cables determine the max transmission distance.

Take an SFP 1G port as an example. It usually supports the copper module, fiber module, and DAC cable.

If you use a 1000BASE-T copper SFP module, the max distance reaches 100m over the cat5e cable.
If you use a fiber SFP module, the max distance reaches 180km over single mode OS2 fiber cable, or 550m over multimode OM2 fiber.
If you use an SFP DAC cable, the max length only supports around 10m.

What is the mainstream speed for SFP ports?

Definitely, 1Gbps and 10Gbps speed is the most common type. But the answer is typically applied to the usual enterprise network, and we should say 8G or 16G SFP for the storage networks.

Can you aggregate multiple SFP ports?

Of course, you can. Link aggregation can provide more bandwidth, redundancy, and load-balancing benefits. That will ensure that one link can immediately switch to a second available link when it fails. So, it is critical for enterprise networks where performance and security are more important.

Sidenote: Make sure you have configured both switches for link aggregation before connecting these ports. Otherwise, it will cause network loops.

Can you connect SFP ports on switches from different brands?

In most cases, you can connect them with different brand switches. But in some cases, you maybe connect them failed.

However, it would be best if you took care of the below tips.

Use the SFP module with the same wavelength on the two slots. But for the BiDi transceiver module, choose the opposite wavelength on two slots. The wrong wavelength will cause failed connectivity.
Check the switch and SFP module compatibility prior. Some large brands like Cisco locked their SFP slots from generic SFP transceivers. Therefore you should better choose an original transceiver. However, You may also order third-party compatible transceivers because those are usually budget-friendly and help to save a lot of money.
Ensure to use correct and quality fiber cable. A wrong fiber cable may shorten the link distance and even fail the link in some wholes. Remember the SMF SFP transceiver only support single mode fiber, while the MMF SFP transceiver only supports multimode fiber (to achieve the longer distance, use OM3 fiber cable instead of OM2 fiber cable)

How Many SFP Ports Does a Switch Have?

The number of SFP ports on a switch may vary depending on different types. A cheap SOHO switch may only have RJ45 port, but no SFP port.

However, a typical enterprise switch for large networks may have 48 SFP fiber ports and one console port. That is because equipped with as many ports as possible to improve the density and throughput.

What is an SPF port?

SPF port is the typing error of it. Because they are unfamiliar with this word, some guys may mistype it and call it SPF port. In fact, they are the same thing.