gdgt

Where there's a will, there's a way. Works on my Airport Extreme
from apple support forums (discussions.apple.com­/thread­/3157398­?start­=0­&t...) :

Unfortunately, the AirPorts are not listed as Xbox Live-compatible routers ... so there is no guarantee doing this will get Open NAT status for Xbox Live!

The following web blog does a great job explaining the NAT issues with Xbox Live! Basically what it comes down to is that although you can get an Internet connection for the Xbox with the AirPorts, you may not get the necessary NAT setting (Moderate or Open) for the Xbox Live! on-line game that you want to play. As such, you basically have two options: 1) Create a DMZ (Apple calls this a Default Host) for the XBox or 2) Configure the AirPort for Port mapping to open the required ports to allow Xbox Live! access ... or 3) Use a compatible router.

Option 1 - Create a DMZ

AirPort Utility > Select the AEBSn > Manual Setup > Internet > NAT
Enable default host at:

Option 2 - Configure Port Mapping

The following ports must be available for Xbox Live to operate correctly:

UDP 88
UDP 3074
TCP 3074

To setup port mapping on an 802.11n AirPort Extreme Base Station (AEBSn), either connect to the AEBSn's wireless network or temporarily connect directly, using an Ethernet cable, to one of the LAN port of the AEBSn, and then use the AirPort Utility, in Manual Setup, to make these settings:

1. Reserve a DHCP-provided IP address for the Xbox 360.

AirPort Utility > Select the AEBSn > Manual Setup > Internet > DHCP tab
Click the "+" (Add) button to enter DHCP Reservations.
Description:
Reserve address by: MAC Address
Click Continue.
MAC Address:
IPv4 Address:
Click Done.

2. Setup Port Mapping on the AEBSn.

AirPort Utility > Select the AEBSn > Manual Setup > Internet > NAT > Configure Port Mappings

Click the "+" (Add) button
Service:
Public UDP Port(s): 88, 3074
Public TCP Port(s): 3074
Private IP Address:
Private UDP Port(s): 88, 3074
Private TCP Port(s): 3074
Click "Continue"