This article is about IP addresses in a private network. Only the "outside" interface(s) of the NAT need to have Internet-routable addresses[5].
Most commonly, the NAT device maps TCP or UDP port numbers on the outside to individual private addresses on the inside. Just as a telephone number may have site-specific extensions, the port numbers are site-specific extensions to an IP address.
In small home networks, NAT functions usually take place in a residential gateway device, typically one marketed as a "router". In this scenario, the computers connected to the router would have a 'public' address to communicate with the Internet. This type of router allows several
