Originally Posted by u3b3rg33k
You'll probably need to turn off NAT for things to work.
That would defeat the purpose completely of his router. That's what his Router will be doing, is NATing the IP he has into his own Subnet, providing IP's to his two XBOX's.
Now, if he had MULTIPLE PUBLIC IP's that would be a different story.
The only problem I foresee is that running from a Single IP, you will always have issues with getting OPEN/MODERATE NAT on both Xboxes.
It's fixable, but not with a public access connection. If it were a Residential connection that allows more than 1 Dynamic IP, it's a piece of cake