IPV4 addresses not working

There are a few reasons why this would happen.

1st - check that your device has an IPv4 address.   IPv4 does not talk to IPv6 and visa versa.    Your IPv4 address should *not* start 169.254.xx.yy

2nd - check that your router received an IPv4 address from Comcast.   If it did not, make sure you have enabled dhcp client on the router.   

3rd - check that your router has a pool of NAT addresses (192.168.0.0/24 for most people though 10.0.0.0/24 works as well) available and that dhcp server is enabled.      This of course assumes that you do not have an external DHCP server running.

The specifics of how you enable dhcp client and dhcp server on your router is going to be firmware dependent and without knowing what your router is, that's the best I can do for you.

If you find that your router has an IPv4 address and your system has an address on 192.168.0.0/24 or 10.0.0.0/24 with a proper default route, then the problem is likely outside of your router.   You can determine where the problem lies using traceroute/tracert 8.8.8.8 and watching for the last router to reply.   The line should have a '!H' or 'H!' somewhere on it indicating that the remote host is not reachable.    The more router hops you have before the host unreachable line the more likely the problem is inside of Comcast and you should turn it over to them for further debugging.

FWIW, my guess here is it's on your side.   If it was further up you would not be the only person with this problem and the further inside of Comcast it is, the more people impacted by it.  😉

this worked for me! 

I used the xfinity app:

1.  open xfinity app on phone (can be on general network)