Open nat on MW3

[Nero]

This worked for me ,lud and shooter in this vid you can also see how to get your ip adress (ipv4) is quite easy just do all that you see in the vid but in the ports you put 3074 instead of the 28960 try it and give your feedback.
Hope this will help.
http://www.youtube.com/watch?v=MxowpBzhDWw&feature=related

Kill you all later.

 

[Silverback]

open and close Nat is easy just put your router ip in task bar.
NOT SURE HOW TO DO THIS THEN CLICK START TYPE CMD. Open dialogue and type ipconfig. This will give you a detail list of your Router along with the Default Gateway "your router ip".
You need the Nat open for mw3 and closed for BF3. If you continue through the set up to advanced settings under the UPNP you can implement the port forwarding for specific games. Incidentally MW3 uses the same ports as COD4.