I found an article on the Linksys 3102 ATA and Asterisk
See http://weblog.infoworld.com/venezia/archives/009482.html
I also found the Linksys web site for the 3102 ATA unit with the User Guide and Firmware updates at
http://www.linksys.com/servlet/Satellite?c=L_Product_C2&childpagename=US...
Would you ditch Cisco for the open source Asterisk IP PBX?
Network World magazine has opinions on both sides. You can add to the discussion yourself.