Port address translation

Port Address Translation (PAT) is a feature of a NAT device that translates TCP or UDP connections made to a host and port on an outside network to a host and port on an inside network.

PAT allows services on multiple inside hosts to appear as services on a single outside host ip address.

In a typical firewall configuration, the outside network is the Internet and the inside network is the LAN.

In a typical DMZ configuration, the outside network is the Internet and the inside network is the DMZ.