There are two ways to play MW3 locally: via System Link (LAN) or via "Private Match" over a local network connection.
(primarily on consoles), the following features are accessible without an internet connection: Can you play MW3 multiplayer offline on PS/Xbox? - Facebook call of duty modern warfare 3 lan multiplayer offline
Launch the game while connected to the internet to ensure all necessary installation and update packs are active. There are two ways to play MW3 locally: