Total aside, but go but a cable modem and return the one Comcast gave you. They're charging you $15 a month for what is likely a $60-$80 modem. They know many folks are just too lazy to replace our don't know they can use their own with a smidge of effort.

Just do a search for "Xfinity compatible modems" for a list of equipment that works. Some sites even have reviews of the best modems specifically for Comcast.