|  |  | Network Address Translation (NAT) is a method of hiding internal IP address information. A firewall or router that translates address information assigns two different network addresses to each interface. The external IP addresses are public, and are assigned or owned by a company; anyone can route or send information to them. Internal addresses may be public or private. Private addresses can be used by anyone but are never routed to the Internet. This is the job of the device doing the network address translation; it changes the internal network's IP address to an available one from an address pool that is assigned to the external interface.