Originally Posted by m00ster
The setting you are describing on your modem where it says ipv4 only is only for the management interface of the modem not the customer interface. You may have full ipv6 service.
the correct setting for comcast ipv6 is the DHCP with PD option. Try setting that and saving/rebooting your router. I have comcast and ipv6 works perfoect for me with the AC66 router.
Wait a second...not all Comcast customers have access to native IPv6 yet.
All of the Arris DOCSIS 3.0 C4 CMTS now have IPv6 but many Cisco CMTS still do not.
It all depends on what CMTS serves your area.
I am in a Cisco area so I have router set to 6to4.
Here is a map of IPv6 enabled areas for Comcast:http://goo.gl/maps/sL3Z
If you are not in one of these areas then you most likely do not yet have native IPv6 available to you through Comcast.