Instructions
Check the Xbox router compatibility chart (see Resources) to make sure your router works with the Xbox console. You can also check to see if your wireless bridge is preventing you from getting online.
Unplug the console from your wall outlet, then plug your Ethernet cable from the back of the console.
Unplug your wireless router from the wall outlet and then unplug the AC adapter from the back of the router.
Allow your router to sit for 10 seconds to reset the Internet connection.
Plug your wireless router back into the wall. Wait until you see the "Activity" or "Internet" light up on your router.
Go to your computer and click on your Internet browser to see if you can get online. If you can, then the router is working.
Log into your wireless router and turn off any "Firewall" settings. You can find out how to do this from the instruction manual that came with your router or by checking the router's manufacturer website.
Plug the Ethernet cable into the Ethernet port on the back of your Xbox console. Plug the other end of your Ethernet cable into an available port on your wireless router.
Plug an Ethernet cable into the "Main Input" of your wireless router and then plug the other end of the Ethernet cable into the "Main Output" of your cable modem.
Plug the Xbox console back into the wall outlet.
Turn on the Xbox console.
Go the Xbox Live dashboard and see if you can get online.