I have Comcast -lrb- nee Adelphia -rrb- cable modem service . bought my own modem back in 2005 I believe , and have be use it since then . finally decide it be time for a upgrade , so purchase the sb6121 after a bit of research . no problem connect it . need to call Comcast support to get it activate : it take longer to find they number and navigate through the automate phone support than it do once the tech be on the line . once I be actually talk to someone , it be a 3 minute process : read she the MAC address , she put it in and reset the signal , and I be up and run . notice a definite jump in my download speed compare to the old modem . only con I would say be the fact that the status light on the front of this modem be not actually label ; they just show various symbol which you need to figure out . they be not that obscure , I would just prefer label . other than that , the modem be great .