Editing Localhost (section)

==Loopback==
{{main article|Loopback}}
The local loopback mechanism may be used to run a network service on a host without requiring a physical network interface, or without making the service accessible from the networks the computer may be connected to.  For example, a locally installed [[website]] may be accessed from a Web browser by the [[URL]] ''<nowiki>http://localhost</nowiki>'' to display its home page.

[[IPv4]] network standards [[Reserved IP addresses|reserve]] the entire address block {{IPaddr|127.0.0.0|8}} (more than 16 million addresses) for loopback purposes.{{Ref RFC|6890}} That means any packet sent to any of those addresses is looped back. The address {{IPaddr|127.0.0.1}} is the standard address for IPv4 loopback traffic; the rest are not supported by all operating systems. However, they can be used to set up multiple server applications on the host, all listening on the same port number. In the [[IPv6 address]]ing architecture{{Ref RFC|4291}} there is only a single address assigned for loopback: {{IPaddr|::1}}. The standard precludes the assignment of that address to any physical interface, as well as its use as the source or destination address in any packet sent to remote hosts.