Network Address Translation
In computer networking, network address translation (NAT, also known as network masquerading, native address translation or IP masquerading) is a technique of transceiving network traffic through a router that involves re-writing the source and/or destination IP addresses and usually also the TCP/UDP port numbers of IP packets as they pass through. Checksums (both IP and TCP/UDP) must also be rewritten to take account of the changes. Most systems using NAT do so in order to enable multiple hosts on a private network to access the Internet using a single public IP address (see gateway). Nonetheless, NAT can introduce complications in communication between hosts and may have a performance impact.