I know a few of us have been having nat issues, and after forwarding all the ports and setting my xbox1 as dhz host, it was still giving me grief. The network settings said my nat was open but cod said it was strict. So one article suggested changing the name of my xbox (figured it makes sense since I have two xbox consoles). Low and behold, a miracle occurred, and that little change and a reset fixed the issue.

Not sure if he his will help anyone else but..