Network address translation (NAT)

Network address translation (NAT)

To overcome IP address limitations, the use of private addresses is commonly teamed with a technique called Network Address Translation (NAT) to provide access to the Internet by hosts that require it. Typically, some device (such as a router, firewall, or proxy server) has a supply of legitimate addresses and translates between a private address and a public one for a host that needs access to or from the Internet.

Note: Some administrators choose to implement IP addressing on their private networks using legitimate addresses (such as 205.254.1.0) that have not been assigned to them. They use NAT to translate between the legitimate external address and the illegitimate internal address. Depending on how the Internet connection works, this may cause problems in the event of a failure in the connection. It is always best to use private address ranges instead.

See Figure 3 for examples of private networks and routers using NAT to translate between private and public IP addresses.