CCNP Routing and Switching ROUTE 300-101 Official Cert Guide

PAT

Port Address Translation (PAT)

A challenge with basic NAT, however, is that there is a one-to-one mapping of inside local addresses to inside global addresses, meaning that a company would need as many publicly routable IP addresses as it had internal devices needing IP addresses. This does not scale well, because a service provider will often only provide a customer with a single IP address or a small block of IP addresses.

Fortunately, Cisco routers support Port Address Translation (PAT), which allows multiple inside local addresses to share a single inside global address (that is, a single publicly routable IP address). Recall that when ...