Other threads indicate a Business Account is required to have multiple IP addresses.
First, check the "Rate Card" for your local area to see if that feature is even available anymore. Seems that it is being phased out;
It's a PDF.
Scroll down to "Xfinity Internet" and look for "Additional IP Addresses".
If nothing is listed then it's likely to have been discontinued in your local market area.
They are phasing it out but I'm going to escalate your issue to the Comcast corporate employees that are available to these boards. We've seen cases here where they have been able to get this accomplished for customers even when it is not listed in their rate cards, YMMV. You should get a reply here in your topic. Good luck !
Please help me add a 2nd IP address to my comcast service.
Thanks for reaching out VK!
Select markets will allow a second IP address for residential accounts. Let's check to see if you live in one of those markets!
Please send me a private message with your full name for help. Just click my name (Comcast_Support) and then on the next page, you'll see an option to send a private message on the right.