when not connected, both entries should be "localhost"
using IP addresses eliminates the need of any name resolution
(eg DNS or /etc/hosts).
You also could load a dummy module
gives you "dummy0" which you can configure like any other NIC.
If you wrap that in a SystemV start-up script you will always
have one interface up. I wont give you any outside connection though.
I am using this for testing only, eg a web-server on my laptop.