The only way I could get the AEBS to connect to the internet was to put it in "bridged" mode.
That would be the correct configuration when the Airport Extreme is used with a gateway device (combination modem/router in one box that most folks call a "modem")
In order to allow the AirPort Extreme to function as the "main" router on your network, you would have to configure the "modem" in Bridge Mode and then setup the AirPort Extreme to "Share a public IP address". The Guest Network option would then be enabled in this type of setup.
Whether or not the gateway can even possibly be configured as a simple bridge only modem is open to question. That would probably be a question for AT&T to see if 1) it is possible, and 2) If they will support it in that type of setup.
If by chance you are using AT&T's Motorola 2210 DSL modem, it is not too difficult to change this device over to simple bridge mode operation...and AT&T will support that type of configuration of the modem.
The only "pitfalls" are that you will have to make some configuration changes on both the modem and the AirPort Extreme.
The upside to this is that the changes will allow the AirPort Extreme to function as the main router on your network....so the Guest Network option will appear if you want to make use of it.
Post back if you need the steps to do this.
Much safer than with Bridge Mode.....which allows anything to pass through. (The NAT firewall is enabled when the AirPort Extreme is configured as the main router)...another good reason to configure things the way that I suggest.
I will post the steps in the next hour or so as soon as I can get other pending online questions answered.
Changes will be made to both your modem and the AirPort Extreme.
To configure the modem:
Enter 192.168.1.254 into your browser and press Enter to bring up the configuration pages for the modem.
Click Advanced on the left side. You may be asked for the modem access code which is on a label on the bottom of the modem
Click PPP Location
Select the “PPP is on the computer or router” setting…or if this does not appear….select the “Bridge Mode” setting
Click Save Changes and allow the modem to restart
Important…..if you ever need to get the modem back to the default settings in the future, you must hold in the reset button on the back of the modem for 8-10 seconds, then enter the 192.168.1.254 address into your browser to set up the modem again.
To configure the AirPort Extreme (AEBS):
Perform a Factory Default Reset as follows:
- Disconnect the Ethernet cable from the modem
- Pull the power plug from the back of the AEBS
- Wait a moment or two
- Hold in the reset button and continue to hold it in for another 8-10 seconds while you plug the power back in to the AEBS
- Release the reset button after the hold period and allow 25-30 seconds for the AEBS to restart to a slow, blinking amber light
Connect the Ethernet cable from the modem to the WAN port (circle of dots icon) on the AEBS
Temporarily, connect a spare Ethernet cable from your Mac to one of the LAN <-> ports on the AEBS. You can disconnect this cable once you have the AEBS set up
Open Macintosh HD > Applications > Utilities >AirPort Utility
Click Manual Setup
Click the Base Station tab located just below the row of icons
Assign a name and password to the AEBS. You can use the same settings that you used before
Adjust Time Zone setting
No check mark needed next to Allow Setup over WAN
Click the Wireless tab next to the Base Station tab
Wireless Mode = Create a wireless network
Wireless Network Name = Your choice. You can use the same name that you used before if you wish
Enter a check mark next to Allow this network to be extended
Radio Mode = Automatic
Radio Channel = Automatic
Wireless Password = Your choice. You can use the same password as before if you wish
Click the Internet icon
Connect Using = PPPoE
Account Name = Your AT&T User Name, probably your email address with AT&T
Password = Your AT&T account password
Service Name = Leave this area blank. No info needed
Connection = Always On
Disconnect if Idle = Never
Click Update at the lower right and allow 25-30 seconds for the AEBS to restart
Close AirPort Utility
Power off both the modem and the AEBS
Power up the modem and let it run a moment
Power up the AEBS next and allow 25-30 seconds for a green light
Check to see if you have an Internet connection on all devices
You can now go into AirPort Utility again, click Manual Setup, and click on the Guest Network tab to enable that feature and assign a Guest Network name and password
Please post on your results
Glad things are working. You now have the correct setup for the AirPort Extreme.
Avoid WDS at all costs.
WDS only runs at "g" wireless speeds, killing all the faster "n" speed capability on your new AirPort Extreme
Worse, it cuts the bandwidth in half on the entire network.
Bottom line....you will have a bit more wireless coverage...but you will have a "g" wireless network throughout running at half speed.
Hopefully, you have an "n" version of the AirPort Express? Then you can use the far faster "extend" configuration and maintain "n" speeds on your network.
Perform a Factory Default Reset on the AirPort Express (AX) like you did before with the AEBS
Temporarily, connect a spare Ethernet cable from your Mac to the AX for the configuration.
Open AirPort Utility - Click Manual Setup
Click the Base Station tab to name the device, assign a device password and adjust Time Zone settings
Click the Wireless tab
Wireless Mode = Extend a wireless network
Wireless Network Name = Same name as your AEBS wireless network
Check Mark next to "Allow wireless clients"
Wireless Security = Same setting as the AEBS network
Wireless Password = Same password as the AEBS network
Update to save changes
Close AirPort Utility as soon as you see the message that the settings have be stored
Disconnect the Ethernet cable
Wait 40-45 seconds for the Express to display a green light
Locate the Express approximately half the distance from the AEBS to the area that needs more wireless coverage and power it up. Avoid walls and obstructions as much as possible in the signal path.
This type of setup will run circles around a WDS configuration.