How do I use the Time Machine command line interface to backup to an internal ip server?
To configure a client to backup to a remote server, you use the tmutil command, and the setdestination verb.

tmutil setdestination afp://user[:pass]@169.254.x.x/share


This also assumes that you have share already existing as an AFP share on your TimeMachine server.

TimeMachine from client-side doesn't really care much about the remote server, except to mount the AFP volume.