Port address translation
lastmod 2018-08-17created 2017-01-132 edits
PAT is a function of network equipment that translates TCP (or UDP) communication between hosts and ports on an external network and hosts and ports on an internal network. The advantage you can expect from using PAT is that multiple internal hosts can be used with a single IP address.
PAT equipment can automatically and transparently modify the destination or source host IP of IP packets and the port fields belonging to internal hosts. In theory, PAT can handle communication for up to 65,535 internal hosts with a single public IP address, but the actual number of hosts allowed varies slightly according to limits preset by each manufacturer.