Sorry. I could no longer edit my last post
Please disregard last solution.
QUOTE(diab0lik @ Feb 26 2009, 01:19 AM)
Also you could just DMZ one of them
A solution I used is this.
Modem <==> Switch <==> Router1 <==>: (My devices)
.................................\==> Router2 <==/ : (My devices)
Connect the WAN on each router to the switch.
Plug your computer into Router1.
Write down the LAN IP address. (usually 192.168.0.1 or 192.168.1.1)
+I will use 192.168.0.1 as an example
Plug your computer into Router2.
Change your LAN IP address to match the first 3 sections from router1. (eg 192.168.0.X or 192.168.1.X, The last number MUST be different from Router1 1-254)
+I will use 192.168.0.2 as an example (Notice the change between routers.)
Disable the DHCP service on Router2.
Plug the LAN ports on the routers together.
There should be 3 free LAN ports on each router that you can use.
It does NOT matter what ones you use.
Plug your computer(s) and Xbox(s) back into the routers. (It dosnt matter what LAN ports you use)
Anything plugged in will automatically connect with Router1.
It will pick up an IP address according to Router1 like 192.168.0.100.
The Default Gateway and DNS will be Router1's LAN IP: 192.168.0.1
You need to manually change the Default Gateway and DNS of the second Xbox360 to Router2's LAN IP: 192.168.0.2, if you want a separate Public IP address.
You can enable UPnP on both routers or setup Port Forwarding on each router.
How this works:
Each Router will pick up its own Public IP address from the Modem through the switch.
When Xbox Live sends something to your Xbox it uses the Public IP address and the Ports.
Now that you have 2(or More) Public IP addresses you can open the ports and your Routers will no longer have to guess what Xbox it is for, as each Xbox has its own Public IP address through each of the routers.