Loopback

A loopback or a loop circuit is a message or an information channel with a single endpoint, so that transmitter and receiver are the same.

In communication technology loopbacks are typically used to test the reachability of a target. In this way, both the communication channel to the target and the target itself is checked. Usually, the communication channel of a plurality of successive transmission sections. By the loop circuit is successively performed on all endpoints of the communication links, the route can be checked to destination and possible suspension be found. Generally, there are various types of loopback:

  • Loopback, in which the remote station the received signal, both loops back to the transmitter, and passes unchanged to the destination.
  • Loopback, in which the remote station the received signal loops back to the sender and the destination of this signal instead of feeding an alarm indication signal.

Loopback on the Internet Protocol

The Internet Protocol ( IP) specifies a loopback network. Specially reserved IP addresses for IPv4, the address space of up to 127 255 255 254 127.0.0.1, where 127.0.0.1 is usually used, and for the IPv6 address :: 1 Most IP implementations support a loopback loop, where all packets, that a computer program sends to those addresses, are addressed to the same computer. The default for domains of these addresses is localhost.

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

The loopback interface is used, among others, the client software in order to communicate with a server on the same computer.

An example: On a computer running a web server. If you supply the browser as a URL http://127.0.0.1/, it will access the web page of one's computer. Since it is no network connection is needed, loopback is quite helpful to examine various services without making them accessible Remote.

Moreover, it is a popular test method to ping the loopback interface, for verifying the correct functioning of the Internet protocol implementation.

Loopback addresses are often used on the internet to perform newbies around by the nose. An inexperienced user who thinks he grab on to a remote server ( Attack or such ) so running, these actions through his own computer. Many users are conscious that 127.0.0.1 is your own computer, but not that (for example ) 127.34.123.43 just refers to them yourself.

Packets with a loopback interface as the sender address, which is sent to an existing IP network can be a large number of problems for older or invalid network software.

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