Checking for the Availability of the Loopback Interface

You should not normally have to manually create a loopback interface because Ubuntu creates one automatically for you during installation. To check that one is set up, you can use the ifconfig command, which lists all networking interfaces available, including the lo interface if it exists, like this:

matthew@seymour:~$ ifconfiglo        Link encap:Local Loopback          inet addr:127.0.0.1  Mask:255.0.0.0          inet6 addr: ::1/128 Scope:Host          UP LOOPBACK RUNNING  MTU:16436  Metric:1          RX packets:270 errors:0 dropped:0 overruns:0 frame:0          TX packets:270 errors:0 dropped:0 overruns:0 carrier:0          collisions:0 txqueuelen:0          RX ...

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