Because the loopback interface responds to all network commands in the same way as a remote host, it can be used to provide limited network testing, such as checking that the correct commands are installed and that all the required drivers are loaded. Because of this, it also provides a useful way of fault-finding network problems by providing another interface to test.
For example, the interface will respond to ping, and its statistics can be displayed using netstat:
hydrogen# ping localhost localhost is alive hydrogen#
The network is “alive,” so let's see how fast it appears to be or whether we are seeing any problems, such as packet loss:
hydrogen# ping -s localhost 64 5 PING localhost: 64 data bytes 72 bytes from ...