- loopbackIP – Loopback Ip address is a special IP number (127.0.0.1) that is designated for the software loopback interface of a machine.
A loopback address is primarily used as a means to validate that the locally connected physical network card is working properly and the TCP/IP stack installed. Typically, a data packet sent on a loopback address, never leaves the host system and is sent back to the source application. When testing network/IP based applications, it is implemented on a virtual network interface card, which acts an addition to the physical network card. This enables users to test an application with an instance of server and client on the same machine, with the ability to transmit network data between, even without access to a physical network.
In IPv4, 127.0.0.1 is the most commonly used loopback address, however, this can range be extended to 127.255.255.255.