Lost IPv6 IP with Comcast


  • I had IPv6 setup with Comcast and everything was working great...until I had an outage. When it came back up, I was unable to grab an IPv6 address on my WAN interface, but internally, I was still able to access IPv6 web sites. I read that maybe if you wait 10 days, it will fix itself.

    Well, unfortunately, ten days later, I lost all IPv6 connectivity and can't get it working again. I've tried to relinquish/refresh, reboot the cable modem, reboot pfsense, and nothing.

    I'm not seeing very much in the logs of either the cable modem or pfsense that indicate any issues. In my WAN interface config, I have "Use IPv4 connectivity as parent interface" and "Send IPv6 prefix hint" checked, and the DHCPv6 Prefix Size set to 60.

    I was hoping that maybe I could get a few hints on what I can do to diagnose the issue and try to figure out what's going on.


  • Well, I kind of figured it out... I'll preface this with I don't know what I'm doing with ipv6. In saying that, numerous posts I've read said to use static addresses on internal interfaces for ipv6 than the track interface thing. What I ended up doing is getting a /60 from Comcast, and setting static IPv6 addresses on my internal vlan's based on the first 3 octets of the IPv6 address. Then, I used the DHCPv6 server and RA service to hand out the ipv6 addresses internally. This kind of makes sense, as I also have firewall rules and it's hard to set firewall rules on dynamic addresses.

    However, by doing it this way, my third ipv6 octet changed from Comcast and threw everything off. It prevented me from getting an IPv6 address on the WAN. Once I set one of my internal vlan interfaces to track, the WAN got an IP and I was able to fix my internal static addresses and dhcp server.

    Hopefully this new address will stick with me for awhile, but I feel like there has to be a better way to do this. Addresses from comcast are issued dynamically and I'm forcing them to static. Same with DHCP reservations....say I have a server with SSH open on it. There must be some way I can get all these updated if the IPv6 address changes. I just don't know how.


  • @qwerty123
    I've got Spectrum and it's the same thing- I have some homelab servers that I don't want dynamic but I have implemented ipv6 internally (dual stack). What I did, right or wrong, was set the WAN interface to DHCP6, and the LAN and 2 VLANs to track, specifying prefix IDs for the VLANs (/56 hint worked). I also set the WAN to NOT send a release to the ISP under DHCP6 Client Config. Instead of using the DHCP6 from my servers, I set that up in PFSense and setup static IPV6 mappings for the servers. But instead of specifying the prefix which we know may change, I set the addresses as ::{interface identifier} hoping that if I don't specify a prefix, and it changes, at least the prefix ID and the interface ID remain as I specified and my servers still get a valid routable IPV6 ip. When it changes I will have to update a couple of ALIASES that list those networks, and some settings under Services/DHCPv6 Server & RA. Hopefully I won't have to mess with the static mappings though.