If it has a coax connector in back (given ATT usually is DSL,) then it may be able to. You will need to get the MAC address from it and provide it to support so they authorize it to be on their system.
This is Comcast Xfinity's supported list: http://www.approvedmodems.com/comcast-xfinity.html
Answers & Comments
If it has a coax connector in back (given ATT usually is DSL,) then it may be able to. You will need to get the MAC address from it and provide it to support so they authorize it to be on their system.
This is Comcast Xfinity's supported list:
http://www.approvedmodems.com/comcast-xfinity.html