WARNING: This information is provided as-is, based on my experience with the specific equipment I have. It may or may not work for you, and if it fails might make your network inaccessible. Please use caution before making use of this information.
AT&T U-Verse provides a pretty decent modem/router (in my case from Motorola). It gives out wired and WiFi local IP addresses, along with handling IP-TV, and if you are like many people is all you need.
On the other hand, if your setup at home needs more you might want to run your own router/firewall/accesspoints behind the AT&T modem/router.
One key part to this is configuring the AT&T modem/router firewall in passthrough mode, so it provides the external IP address to your router.
Using a laptop, connect to the AT&T modem/router. The address and login information is usually on the side/bottom of the device, e.g. 192.168.1.254.
Select Firewall options-> IP Passthrough to open a new tab, then pick:
- Allocation Mode: IP-Passthrough
- Passthrough Mode: Manual
- Passthrough Fixed MAC address: WAN MAC of *your* router.
Then Save the changes. You will need the AT&T Modem/Router access code. This is usually on the side of the device, and is a string of numbers/letters/symbols.
After this is done you need to Restart the AT&T modem/router (which takes a few minutes). Once that is done, connect your router to the AT&T modem/router and release/renew the WAN DHCP address. You should get an external address instead of the previous 192.168.1…. address.
If you are using a different access point (e.g. an Apple AirPort) in your LAN you may also want to disable the default WiFi in the AT&T modem/router. This is done through the modem Wifi management tab.