Whoever branched the discussion,, nice one.
Corv , can you please answer the following:
What platform are you playing on?
What is your platform's NAT type? What is your in-game NAT type?
Do you have any of Upnp, Port Forwarding, or DMZ used in your router?
Have you given your platform a Static IP?
In the mean time please read: Achieving Open NAT - port numbers included. Ghosts V2