XBOX Live requires the following INBOUND ports be open on your network, but are normally blocked by your router’s firewall for security reasons.
Port 88 (UDP)
Port 3074 (UDP and TCP)
Port 53 (UDP and TCP)
Port 80 (TCP)
You have three options (from harder to easier).
1. Manually open and forward these ports on your router’s firewall to the IP address of the XBOX (see http://www.portforward.com
2. Place the IP address of the XBOX in the DMZ of the router.
3. Enable UPnP (Universal Plug and Play) on the router (the XBOX will then automatically open and close the ports on the router as it sees fit).