Network Address Translator (NAT)

A NAT device is a device that will translate one ▲IP address into another IP address. Generally, this includes the translation of a port number into a different port number, though not necessarily.

NAT devices are useful in networks where there are limited public addresses or where there is a desire to hide the topology of an internal network from the outside world.

NAT devices break the fundemental end-to-end principle of the Internet. Even so, they are a fact of life, as virtually every enterprise network and home network relies on NAT devices in order to access services on the public ▲Internet.

NAT devices are generally integrated with ▲firewall devices, but the functionality of the two devices are quite different in scope and purpose.