Instructions
Connect two PS3 consoles together with an Ethernet cable. Connect one end of the Ethernet cable to one PS3 in the Ethernet port and then connect the other end of the Ethernet cable to the other PS3's Ethernet port.
Turn on the first PS3 and load the "Call of Duty" game.
Click on the "Multiplayer" icon from the Main Menu. This sets up the first console as the host console.
Click on the "System Link" icon and then press the "A" button.
Click on the "Create Game" icon and then choose the kind of game that you want to play. Click on the "Start Game" icon.
Turn the other console on and click on the "Multiplayer" icon. Click on the "Join Game" icon and find the game on the list that appears.
Click on the game to join it.