Sysadmin Field Notes

May 2, 2008

In case it helps, here's the steps I used to setup my Airport Extreme in bridge mode behind the ATT Uverse RG 2wire gateway thing. I previously had the DSL modem with ethernet out, into the Airport, letting it act as the router. I like and would prefer that configuration I think, but the RG doesn't have bridge mode. So if you leave things set like this, you'll have two levels of Network Address Translation (NAT) going on. Which works fine for some things and terribly for others. That includes anything that needs to allow ports back in, like iChat or other A/V things, bit-torrent, etc. It's not that it can't be made to work in some cases with careful port forwarding, but it's a hassle.

So the way we want to configure things is such that the RG is the router; it will do all the DHCP stuff; get its IP from ATT, and then act as an internal DHCP server so things on your home network get IP addresses. Luckily, this is the immutable default configuration. :-) We'll probably also want to disable it's wireless network, just to avoid interference with your existing network, or your neighbors, etc. since we we prefer the Airport's wireless network.

For the Airport, we'll need to configure it in bridge mode. This disables its DHCP server, router and firewall. Now it's essentially just a dumb switch; it's just passing traffic between it's ethernet ports and the wireless network. So when a computer connects to the airport network, it will ask for an IP via DCHP. The airport will no longer answer that request from it's own pool, but instead pass it onto it's ethernet, where it will get to the ATT provided gateway. Then the gateway will give the wireless computer it's IP address and route traffic to it. We'll also want to set the Airport to get its IP via DHCP from the ATT gateway as well, so it can have an IP for printing or disk use, etc..

A word of caution before we begin, you will likely lose connectivity briefly during this procedure, so be prepared. Don't be 99% way through a 20GB download when you do this.

So let's get started. First the airport. Run "/Applications/Airport/Airport Utility". You should a screen showing all airports (I have an express and extreme). Select your desired Airport, and you should see this:

Click on manual setup at the bottom (circled in the above shot, then click "Internet" up at the top. You should see this:

On "configure IPv4", set it to "Using DHCP". This will give your airport an IP you can connect to. Then under connection sharing (highlighted), choose "Off (Bridge Mode)". Now click update. If I remember, I think it reboots, or does something that takes a few seconds. You'll probably lose your connection to it initially.

So now you might be a bit stuck, you may/may not be a bit stuck, since your computer probably has an IP that your airport gave you, but now you're talking straight to the RG for routing. No worries, you can either reboot your computer, or follow Apple's procedure for getting a new IP. Skip to the "Solution->Mac OS X instructions -> 1. Force reconfiguration of IP Settings" section. Or just reboot. Any other network hardware that got it's IP from the airport will need to be rebooted as well.

Now, any computers plugged into the Airport extreme ethernet ports or wireless networks should be getting their IP from the RG and using it properly. Before you started, if you looked at your RG configuration screen in the Home Network section, you would have just seen the airport extreme. Now you should see all your devices showing up.

You can get to this screen by trying this configuration URL (which is pointing at your router), or manually visiting http://192.168.1.254/ in your browser.

Now the final step if you don't want to use the RG's wireless networking at all, is to disable it. From the screen above, click Home Network and you should go here:

Notice the circled button on the right; "Disable" next to the wireless network. Click that. You'll get prompted for confirmation, and the device password. Once done, the button changes to "Enable", which you can click to re-enable the wireless should you ever choose to.

That's it; with the Apple acting in bridge mode, the RG is in charge. Seems to work fine for me so far, no complaints. Note you can still have the Airport participate in a WDS network even in bridge mode; I'm using it with my Airport Express that way.

Update 4:00PM PST Fixed broken image