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Forum Discussion
Solved
CM1100 IPv6 Problem (Xfinity)
Hi everyone,
I replaced our C7100V with a new CM1100 yesterday. After a bit of wrangling on the phone with Comcast, it's activated and working... but only on IPv4. Firmware version after the Comcas...
CM is just a bridge modem. It is not do anything for CPE side (LAN side) Ipv6 other than just mere forwarding it.
Comcast does DHCPv6 for the routers and provides a delegated Prefix (PD) along with it.
Not sure what firewall you are using, but most linux ones support DHCPv6 with PD.
Update 1:
After working with a customer expert on the Comcast forums (not an employee), I've got some more data. Plugging a laptop directly into the port I used for the firewall and power-cycling the CM1100 resulted in the laptop pulling an IPv6 address (2001::x) and Class A IPv4 address. Plugged the firewall back in, power-cycled again, and it still didn't get an IPv6 address.
Thought 1: Perhaps Comcast only issues addresses to its gateways via DHCPv6 and since the firewall only supports SLAAC/RA, that's the issue?
Thought 2: Could I take the IPv6 address the laptop pulled when I connected it directly to the CM1100, and set that as a static address on the external firewall interface?
Thanks, and happy Friday!
Update 2: Let's mark this as "solved," since the CM1100 is indeed pulling an IPv6 address. I'll continue working the issue with Untangle, since it's likely related to an issue with DHCPv6 / Native IPv6 / stateless / PD / RA, or a block of ICMPv6 traffic.
Thanks!
One final question about the CM1100 - will there ever be an ADVANCED > Advanced Setup > IPv6 settings page for the CM1100, like with other Nighthawk products?
Thanks!
I know little about IPv6, but ...
> [...] the CM1100 is indeed pulling an IPv6 address. [...]
The CM1100 is a modem, not a (modem+)router. What does it care about
IPv<Anything>? I'd expect a router, or your "our firewall (Untangle
v14.1.1)", to care about such things, but not a simple modem.> One final question about the CM1100 - will there ever be an ADVANCED
> > Advanced Setup > IPv6 settings page for the CM1100, like with other
> Nighthawk products?As with _which_ "other Nighthawk products"? Do you mean Nighthawk
(modem+)_router_ products? I wouldn't hold my breath.CM is just a bridge modem. It is not do anything for CPE side (LAN side) Ipv6 other than just mere forwarding it.
Comcast does DHCPv6 for the routers and provides a delegated Prefix (PD) along with it.
Not sure what firewall you are using, but most linux ones support DHCPv6 with PD.