So I have been surfing the internet looking up how to have two xbox 360s, which share a home network, with open NATs. At the moment, I have tried port triggering, port forwarding, and DMZ (and all 3 together just for kicks ). I currently have a Motorola SURFboard SB6121 modem connected to my TRENDnet TEW-639GR 802.11b/g/n router. We have two xbox 360s in my apartment with live accounts and are trying to both play online at the same time.
What we have tried so far allows one of us to have an open NAT and the other to have a moderate or strict NAT. I read some articles online about switches and how they could alleviate this issue. I wasn't so sure whether or not that would work. By having both of the xbox 360s plugged into a switch, which would be connected to my router, would that allow both consoles to have an open NAT? I also read about purchasing another public ip from an ISP could solve the problem but I am not so sure I want to be giving more money to Charter.
The problem is that the XBOX uses well-defined, fixed ports. And since you MUST use those same ports externally, and your router can only forward any given port to one internal IP address, you're stuck. It's not like say, a webserver running behind your router. In that case, even though every webserver defaults to port 80, you can easily run two webservers by defining two external ports (say, 8080 and 8081) and forwarding each to their respective internal IP addresses. But again, when it comes to the XBOX, as far as I know, you don't have this option.
Even using a switch won't help because there's no way to know for any given unsolicited, inbound traffic, which XBOX is the intended target. As far as XBOX Live is concerned, there's only one public IP and it always sees your network as having a single XBOX. There’s simply no mechanism to decide whether the traffic should be forward to XBOX #1 vs. XBOX #2. That information gets lost because it’s the public IP that makes that possible, but you only have the ONE public IP!
This is simply a limitation of NAT routers.
To make a long story short, there's no real way to solve the problem short of having a second public IP so that you can associate each XBOX w/ its own public IP. And then XBOX Live will see those XBOXes as distinct devices.