I had this problem a little while ago but my brother helped me solve it. First thing you want to do is find your IP Adress. To do this, go to the Start Menu, and click "Run".
Type "cmd" in there and you will get command prompt. Now in Command Prompt, type "ipconfig".
When this comes up you will get a list of different things. Using the number labeled "default gateway", type that number into the bar at the top of your web browser. If it's the correct number, you'll be prompted for your router username and password. First try "admin" and "password" respectively, because these are the defaults for any router. If this doesn't work, then you'll have to find what they are, I can't help you with that. Once you get to your router page, (IF you get there) look for a button that talks about Ports, mine says "Port Forwarding/Port Triggering". Click on that, and then add a new port. Name it whatever you want, and then put 5029 in the other two boxes. Fill in the IP Address box with your IP Address from command prompt, NOT the Default Gateway one, the one that says IP Address. Click apply, and you should be ready to go. You can check if it's working by going to the master server once you've started your netgame and seeing if it has the information on it.
