Airport Time Capsule and AT&T Uverse BGW210-700

I am posting the following for those who are looking to set up or having problems setting up an Airport Time Capsule (TC) with AT&T's Uverse residential gateway (RG) model BGW210-700 (I think other models could use this solution as well).

I recently switched from comcast to AT&T Uverse internet service. This became a problem immediately: double NAT and could not see the TC in the Airport Utility. The TC showed a solid and sometimes blinking yellow light. My Time Machine backup capability on my iMac was gone; the drive was not available.

After reading many online solutions (dated back from before 2010 to the most recent on AT&T forum and other forums), I have found a setting on the BGW210-700 and TC that worked for me. My setup is as follows: AT&T BGW210-700, iMac (connected wirelessly), iPad (connected wirelessly), and Airport Time Capsule (wired via ethernet cable). Last important detail of the setup: McAfee antivirus software on iMac.

Have the following handy:

Access to the AT&T router: 192.168.1.254 and the necessary access codes that can be found on the router's label.

The MAC address of your TC.

iMac with Airport Utility

iPad that has Airport Utility (for some reason, even though the TC disappeared from the Airport Utility on my iMac, the app on my iPad did not have a problem)

Modify the settings on the BGW210-700:

(just a precaution, should your network somehow be rendered inoperable, there is a reset button on the router that would return the router to its original setting when installed by the AT&T tech)

Access the router by typing into a browser "192.168.1.254"

Disable wireless of the router by selecting Home Network > Wi-Fi (enter access code) > select "Off" under Wifi operation for both 2.4 and 5 GHz.

Go to Firewall > Packet Filter > disable Packet Filters

Go to Firewall > IP Passthrough > Select Allocation Mode as "Passthrough" > Select Passthrough Mode as "DHCPS-fixed" > Choose your TC from Device List or enter manually the MAC address in the blank field > select Save.

Go back to the first screen Device\Status to confirm that the Wi-Fi is off for both bands, then select Restart Device.

Modify the settings on TC:

Make sure Internet setting is using connection type DHCP.

Go to Network > select Router Mode as "DHCP and NAT"

Go to Disks > make sure that check boxes are checked for Enable file sharing and Sharing disks over WAN.

The update the TC by selecting the Update button at the bottom.

Reboot your iMac.

After all routers have been rebooted, bring up the antivirus console. Under the file menu at the top of the screen, select Preferences. Go to Firewall and select the Reset Firewall button.

After the reset of the firewall you should be able to see the TC on the Airport Utility of your iMac.

(That's how it happened for me. I think the main problem here is the antivirus program that somehow blocks the access to the drive on your TC.)

I hope this will help you resolve the problems with your network and bring back the Time Machine into action.