Xfinity provides only the two in one (modem and router) for internet access. They do not encourage you to use your own modem and router but will connect through them if you start with an Xfinity approved modem.Check the Xfinity website for approved modems.
It's a wireless gateway which means it's a modem router combo. Docsis 2 and 3
Thanks! Your answer is awaiting moderation.