Connecting a Tomato Based Router to an AT&T U-Verse 2wire 3600HGV Residential Gateway
A few months ago I decided to replace my DSL service with AT&T U-Verse. My prior DSL modem was pretty straightforward, one wire to street service, the other into the router. By necessity, the router provided all other networking and firewall functions.
The AT&T U-Verse Residential Gateway is a totally different animal. By itself the AT&T U-Verse supplied hardware appears to be a very capable DHCP server, firewall, and wireless access point. This means that simply plugging in a router behind the AT&T gateway will not work without making some changes. Different approaches can be taken, but I wanted to use the Tomato based router as the primary network device, thus the need to disable most of the residential gateway routing features.
Fortunately AT&T provided capable software tools to modify the residential gateway to work happily with Tomato based routers. Following are steps for the AT&T U-Verse 3600 HGV Residential Gateway. Another very good set of instructions for the can also be found here for a similar but different model U-Verse Gateway.
Get an Ethernet cable; physically plug your computer/laptop into one of the four Ethernet connections in the rear of the AT&T U-Verse 3600 HGV Residential Gateway. Leave your Tomato router connected in a second port and powered on. The other two hardwired Ethernet ports should be empty.
Restart your computer/laptop then launch your internet web browser and type 192.168.1.254 to reach the AT&T U-Verse administrative console.
First task, disable wireless. Your Tomato router's wireless needs to be the main wireless system for you to maintain Quality of Service (QOS). Click on the LAN tab, then click on "Wireless" below.
Change the Firewall to "Allow all applications (DMZplus Mode)". Select the Firewall Tab, then click on "Applications, Pinholes and DMZ". Make sure you chose the router (and not whatever computer you are using) under Step 1. Under some scenarios, the router is labeled "unknown". If you assign the gateway a static IP from within Tomato, that name will appear in the Gateway list as is shown in my example. See Step 2 under part B below.
Save all your changes.
Disconnect your computer/ laptop and re-boot the AT&T U-Verse Residential Gateway
With an Ethernet cable, plug one end into the port 1 on the AT&T Residential Gateway and connect the other end to the WAN port of the Tomato Router. Do not make any other connections to the AT&T Residential Gateway; always leave the other three Ethernet receptacles unused. All further hardwire and wireless connections must pass through the Tomato router. If you need more than the usual four hardwire connections built into most standard routers, purchase an Ethernet switch and connect it in downstream of the router to provide additional plugs.
With an Ethernet cable, connect the AT&T U-Verse Residential Gateway to the Tomato Router. Connect the cable to port 1 in the rear of the gateway to the WAN port on the router.
OPTIONAL COOL STEP - To avoid future hassles associated with moving wires around, it is possible to configure your network in a way to get access to the administrative panel of the AT&T U-Verse RG console via your computer, through your Tomato router, by changing subnets.