Loopback

A loopback is a communications channel with only one endpoint. Any message transmitted through such a channel is immediately received by the selfsame channel.

The .

On Unix-like systems, the loopback interface is commonly called lo or lo0.

A loopback interface has several uses. It may be used by network client software on a computer to communicate with server software on the same computer -- viz., on a computer running a the loopback interface is a basic test that one s IP stack is working properly.

Loopback addresses are the subject of a reasonably common Internet prank: directing an inexperienced user to connect to (or attack) his own loopback interface as if it were a remote server [http://bash.org/38640].

Packets sent on a real IP network with a source address on the loopback interface can cause a number of problems for older or buggy network software. Such packets are known as martian packets . [http://www.catb.org/~esr/jargon/html/M/martian.html]