What Is NAT?

NAT stands for network address translation. It’s a way to map multiple private addresses
inside a local network to a public IP address before transferring the information onto the internet. Organizations that want multiple devices to employ a single IP address use NAT, as do most home routers. If you’re connecting from your home right
now, chances are your cable modem or DSL router is already providing NAT to your home.

How Does NAT Work?

NAT stands for network address translation. It’s a way to map multiple private addresses inside a local network to a public IP address before transferring the information onto the internet. Organizations that want multiple devices to employ a single IP address use NAT, as do most home routers. If you’re connecting from your home right now, chances are your cable modem or DSL router is already providing NAT to your home.

Let’s say that there is a laptop connected to a home network using NAT. That network eventually connects to a router that addresses the internet. Suppose that someone uses that laptop to search for directions to their favorite restaurant. The laptop
is using NAT. So, it sends this request in an IP packet to the router, which passes that request along to the internet and the search service you’re using. But before your request leaves your home network, the router first changes the internal
IP address from a private local IP address to a public IP address. Your router effectively translates the private address you’re using to one that can be used on the internet, and then back again. Now you know that your humble little cable modem
or DSL router has a little, automated translator working inside of it.

If the packet keeps a private address, the receiving server won’t know where to send the information back to. This is because a private IP address cannot be routed onto the internet. If your router were to try doing this, all internet routers are
programmed to automatically drop private IP addresses. The nice thing is, though, that all routers sold today for home offices and small offices can readily translate back and forth between private IP address and publicly-routed IP addresses.