Editing IP address (section)

==Address translation==
Multiple client devices can appear to {{anchor|shared_IP}}share an IP address, either because they are part of a [[shared web hosting service]] environment or because an IPv4 [[network address translator]] (NAT) or [[proxy server]] acts as an [[intermediary]] agent on behalf of the client, in which case the real originating IP address is masked from the server receiving a request. A common practice is to have a NAT mask many devices in a private network. Only the public interface(s) of the NAT needs to have an Internet-routable address.<ref>{{Cite book |last=Comer |first=Douglas |url=http://www.cs.purdue.edu/homes/dec/netbooks.html |title=Internetworking with TCP/IP:Principles, Protocols, and Architectures – 4th ed. |publisher=Prentice Hall |year=2000 |isbn=978-0-13-018380-4 |location=Upper Saddle River, NJ |page=394 |archive-url=https://web.archive.org/web/20100413232359/http://www.cs.purdue.edu/homes/dec/netbooks.html |archive-date=13 April 2010 |url-status=live |df=dmy-all}}</ref>

The NAT device maps different IP addresses on the private network to different TCP or UDP [[port number]]s on the public network. In residential networks, NAT functions are usually implemented in a [[residential gateway]]. In this scenario, the computers connected to the router have private IP addresses and the router has a public address on its external interface to communicate on the Internet. The internal computers appear to share one public IP address.