Me and a friend have been trying for days to connect our two ps3 systems together so we can play one on one MW3. We try connecting with an ethernet cord but it never detects it and when we try to go into LAN party it just says no internet connection detected. or that i have to be signed in. I connected both playstations to the same router wirelessly, signed them in, and tried to connect them via Private match invites but it isnt working, it immediately says Unable to join Lobby. HELP???!!!!!
Once you are both connected, you should be able to setup a private match and invite them.