Gaming from behind a router - how do I determine the proper IP of my server?

Hi dudes and dudettes.  trying to play a little cod2 manno a manno with a bro and I am having trouble getting him to connect to my server - I thought I figured out my IP address but there are two computers connected to this particular router, and both are acting as if they are at the same IP . 

to outline things completely, we are on citytel ppoe adsl, and the modem goes into a hub, the hub line comes upstairs and plugs into the wireless router and from there it goes out to the 2 laptops.  So is there some easy way I can determine the proper IP for my computer? or make the router assign my computer a real, working IP address?  It is an apple airport with airtunes if that makes anything easier. thanks

mu will tell you the external ipaddress.

that IP came up when I checked it on my other laptop too though.  So the router will figure out which computer is the right one when he tries to connect?

Any other reason that my buddy wouldnt be able to connect to me then?  Should I have to setup something with the router re: the correct port being open so the game server can see his “Yo”?

No you haveto do port forwarding to that computer that you want to game on. I don’t know if the airport express does this or not. Never used one yet.