AXE5300

No. It's DHCP / automatic configuration. What is the exact make and model number of the cable modem that you will be using with it ?

I should have known it was DHCP. I've researched this further and I have to use the Delco AXE5300 in the AP mode, and allow the CGM4331COM to handle the overhead. That way I can still take advantage of Xfinity security on the gateway. Is that correct?

Correct. That would be the only way to utilize any of the Xfinity features / Xfinity app. That may or may not be an advantage depending on your point of view / networking equipment  knowledge / desirability for reliability, and other factors like a lack of very useful features when using an ISP's equipment.

There is another way to go. It is to put the Xfinity gateway device in to bridge mode so that it acts only as a plain vanilla cable modem, and let AXE5300 handle your routing / WiFi / home networking needs. In my experience, you will likely be happier with the latter setup. 

You can go that one better and discontinue renting the gateway and buy your own compatible straight cable modem to use with the AXE5300. You'll save the rental fee and the cable modem will pay for itself in fairly short order. You likely get all around better performance with the latter setup !