I have had strict NAT on ghosts ever since installing. I just looked online and found a possible fix. I have just tried it and my NAT is open for the first time 
Go to following website and click 'Follow a guide located here'. Then just pick router, then pick game (ghosts isn't on there yet so I selected Call Of Duty - Black Ops II). Follow instructions and let me know if it works for u too.
Link ---------> http://portforward.com/
Go to following website and click 'Follow a guide located here'. Then just pick router, then pick game (ghosts isn't on there yet so I selected Call Of Duty - Black Ops II). Follow instructions and let me know if it works for u too.
Link ---------> http://portforward.com/