People in this thread saying they lose Comcast service by op’s dad having their own modem obviously haven’t tried to use Comcast’s “service” ever. It’s not existent. Comcast goes out of their way not to help you no matter what service you have and no matter what modem you have. Buy one of their supported modems and they will still support it… The same crappy way they support their own modems. Source: I have my own modem on residential Comcast service and I also run a number of businesses that have Comcast equipment and there is no difference in the service level.