For many years I have been an ADSL subscriber receiving 3 Mbps service from AT&T. The line came into the house and into a simple ADSL modem that connected to a Linksys WRT54GL running DD-WRT firmware, which was setup to serve as the Internet gateway for all computers in the house. I won't go into the virtues of this particular model of Linksys router running this particular firmware, but suffice it to say that those who know what I'm talking about will need no further explanation.

Recently, we moved to a new house and AT&T would not let me transfer the ADSL line to the new address, but they said they would be happy to set me up with this shinny new digital service they call UVerse. After doing some checking, I noticed that the reviews from customers were mixed, but that the speeds provided were pretty decent. I was leaning towards cable service, but the wife likes AT&T, so we signed up for the 12 Mbps UVerse Internet plan.

The AT&T technician came to the house and set it all up in the phone box outside — inside the house he hooked the line up to a 2Wire 3600HGV device. When he saw my Linksys router laying nearby, he said "With this beauty right here..." and he showed me the 2Wire device, "... you won't need that Linksys router of yours." That should have been my fist sign that something was amiss.

The one redeeming quality of the 2Wire device is that it does have a really strong radio signal, but other than that the firmware running on it is really crippled and perhaps can do a little more than 10% of what the DD-WRT firmware is capable of. The conspiracy theorist in me says that the 2Wire hardware and software are probably more capable than AT&T is willing to document and let the users have access to,

Anyway, the ideal situation for me was to turn the 2Wire into a dumb modem and use my Linksys as the gateway, just like the old ADSL days... but that was easier in concept than in practice. There are all kinds of gotchas and tricks to get it setup, like the Router Behind Router detection. After much trial and error, I persevered, and below is the result of my research into how to get this setup to work.

At this point I recommend that you make a backup of your current DD-WRT setup by going to Administration and then the Backup menu and then clicking the Backup button.

The first step is to get the Linksys router ready for the setup. Make sure you can reach it and connect to it with a browser by going to http://192.168.1.1/. I used an Ethernet cable directly from my laptop and into one of the 4 LAN ports on the Linksys. Once you logged in to the Linksys, go to Setup and then Basic Setup. Under WAN Setup, make sure that the Connection Type is DHCP and give the device a unique Router and Host name. Under the Network Setup area, change the Local IP Address to something like 10.0.0.1 — just make sure that the IP you choose is in a different subnet than 192.168.1.X. With this setup we are trying to avoid conflicts between the Linksys DHCP and the 2Wire DHCP servers and in general we want the 2 devices in separate networks anyway.

The next step is to connect to the 2Wire device. I unplugged the Ethernet cable from the Linksys and connected it to one of the LAN ports on the 2Wire. Now you should be able to reach the 2Wire setup interface by pointing your browser to http://192.168.1.254/. If at first you are unable to connect, then check your current IP address. Since the Linksys was changed to a different network, you may have gotten an IP in the range 10.0.0.X. You can fix this by releasing and renewing your IP lease. Also, in order to apply any changes to the 2Wire device you will need to know the System Password which should printed on a label on the device.

Before moving on, I want you to consider the above image for a moment. Here's what's going on:

1. The blue ethernet cable connects the the 2Wire device to the WAN Port on the Linksys.
2. The yellow ethernet cable was used to connect the laptop directly to the 2Wire device and also to the Linksys previously.
3. The green RJ11 cable is the digital data cable connecting to the Internet at large.
4. The white RJ11 cable is for the phone/voice service and goes into the telephone set.

As you can see in the above image, the blue cable connected to the 2Wire device terminates into the WAN port of the Linksys device.

Now, back from this little tangent, I was about to connect to the 2Wire device with the browser. Once connected, go to Settings and the LAN tab and click on the Wireless link and ensure that the value under Wireless Interface is set to Disabled. I want the Linksys in charge of providing Wireless and DHCP services. Once that's done, click the Save button at the bottom of the page.

Next I need some way for the Linksys to receive all inbound Internet traffic into the house. This can be done by putting the Linksys in DMZPlus mode in the Firewall setting of the 2Wire device. Go to the Settings tab in the 2Wire setup interface and then click on the Firewall tab and click on the Applications, Pinholes and DMZ. Choose the DD-WRT (or whatever name you gave your device) from the list under Select a computer. Then further down on that same settings page under Edit firewall settings for this computer select the choice Allow all applications (DMZplus mode). Make sure to click the Save button at the bottom of this page when all done.

You can verify that the 2Wire setup is correct by going to the Status page under the Settings and Firewall sections and seeing that the DD-WRT device is listed under the Current Applications, Pinholes and DMZ Settings: Custom and that it was assigned a public Internet IP.

One more side bar is called for at this point in the setup process. If at any point in time during the setup you are faced with a warning from the 2Wire device that it has detected a Router-Behind-Router setup, please just ignore it as the final outcome of the setup I am doing will render that type of detection irrelevant. As a matter of fact, while on the 2Wire setup interface, just go to the Settings tab and then the System Info tab and the Event Notifications link and make sure that the option Enable detection of router-behind-router conditions is not checked. Save your change before moving on.

Let's do a quick recap: We first put the Linksys device in DHCP mode at the WAN level and gave it a recognizable name, then we gave it a different subnet IP than the default 2Wire IP. Next we disable the Wireless service on the 2Wire device and then we put the Linksys device in DMZPlus mode in the 2Wire configuration screens. We also verified that the Linksys is getting a public IP from the 2Wire perspective.

Next we need to ensure that the Linksys is getting the public IP address from it's own perspective (see above image). Go to the Status tab and then the WAN tab on the DD-WRT setup interface. Under the WAN section on that page ensure that the IP Address value is the same as the one assigned to the DD-WRT in the 2Wire interface. I obfuscated the public values here for obvious reasons.

This is where I was a little stumped when I went through these steps for the first time. If at first your Linksys/DD-WRT doesn't recognize the public IP, try using the DHCP Release button or rebooting the Linksys. I had to reboot the Linksys twice initially, but it has been working for me without any issues for a week now.

I hope this write up is useful to you...