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I messed around with IPv6 on Comcast for a while. They claim very high levels of residential deployment, yet when you head to their forums to troubleshoot it,

I messed around with IPv6 on Comcast for a while. They claim very high levels of residential deployment, yet when you head to their forums to troubleshoot it, their top IPv6 agent--who seems to know his stuff--generally comes back with things like "yes, that is broken," or "we're still working on a fix for that." Years later, still no fix.

sigjuice 8y ago
Could you please share a couple of examples of things broken with Comcast IPv6? Thanks!
- jstewartmobile 8y ago
  From what I recall it had to do with static IP configuration under dual stack. If you're residential, it doesn't apply.
MrRadar 8y ago
I'm using IPv6 on Centurylink who don't even deploy IPv6 by default (they have a 6RD server but their default modem/router config doesn't use it and you have to dig on their site to find it) and IME after configuring 6RD on my modem IPv6 "just works" for both incoming and outgoing connections. I'd be surprised if Comcast weren't at least as good as Centurylink.
- HankB99 8y ago
  I had problems with Ubuntu updates hanging and the fix was to do something that (I think) caused networking to prefer IPV4. I'm on Comcast but don't know if the problem was theirs. If networking preferred IPV6 prior to the change and only one site gave trouble, I'd be inclined to blame something specific to that site or the route involved.
markovbot 8y ago
I've had Comcasst IPv6 for the last few years, none of the issues I've encountered with IPv6 were Comcast's fault. What sort of problems did you encounter?
- deathanatos 8y ago
  I have a Comcast business account. I've had an IPv6 address for a few years, and generally, it has worked exactly as expected. I've had two outages that are notable: 1. an outage where v6 traffic was just dropped, period. It took a service call, but was fixed within a day, IIRC. It was no more or less painful than any other service call. 2. an outage where v4 TCP SYNs were dropped, mostly; once a connection was established, the connection was fine. AFAICT, this was some issue, perhaps HW failure, with their modem/router combo. Once the router was replaced, the issue was fixed. This took several days to correct, mostly because it was difficult to convince Comcast's techs that the physical copper cable is probably not discriminating against IPv4 traffic. My experience w/ their business division is that the support agents have some light experience. My experience w/ their residential side is that the support agents have never seen a computer. The rollout to business was after the rollout to residential; I also filled out a form requesting one way back in the day when they were essentially polling for interest.
  - cjcampbell 8y ago
    > This took several days to correct, mostly because it was difficult to convince Comcast's techs that the physical copper cable is probably not discriminating against IPv4 traffic. I'm torn between laughter and intense anguish. I'm afraid to even estimate how many days of my life have been spent honing my rhetorical skills to convince a support agent of similar points.
FireBeyond 8y ago
Right. Last I checked (business), with a static IPv4... IPv6 worked with one of the four available modems. If you had that one modem, you got dynamic IPv6, static wasn't supported. With your dynamic IPv6, you then had to modify your SLAAC(?) / DHCPv6 because of an incongruity between what the modem was saying, and what would work (I believe it said you had a /56, but you could only advertise a /64 internally). And so on.

sigjuice 8y ago

Could you please share a couple of examples of things broken with Comcast IPv6? Thanks!

jstewartmobile 8y ago
From what I recall it had to do with static IP configuration under dual stack. If you're residential, it doesn't apply.

MrRadar 8y ago

I'm using IPv6 on Centurylink who don't even deploy IPv6 by default (they have a 6RD server but their default modem/router config doesn't use it and you have to dig on their site to find it) and IME after configuring 6RD on my modem IPv6 "just works" for both incoming and outgoing connections. I'd be surprised if Comcast weren't at least as good as Centurylink.

HankB99 8y ago
I had problems with Ubuntu updates hanging and the fix was to do something that (I think) caused networking to prefer IPV4. I'm on Comcast but don't know if the problem was theirs. If networking preferred IPV6 prior to the change and only one site gave trouble, I'd be inclined to blame something specific to that site or the route involved.

markovbot 8y ago

I've had Comcasst IPv6 for the last few years, none of the issues I've encountered with IPv6 were Comcast's fault. What sort of problems did you encounter?

deathanatos 8y ago
I have a Comcast business account. I've had an IPv6 address for a few years, and generally, it has worked exactly as expected. I've had two outages that are notable: 1. an outage where v6 traffic was just dropped, period. It took a service call, but was fixed within a day, IIRC. It was no more or less painful than any other service call. 2. an outage where v4 TCP SYNs were dropped, mostly; once a connection was established, the connection was fine. AFAICT, this was some issue, perhaps HW failure, with their modem/router combo. Once the router was replaced, the issue was fixed. This took several days to correct, mostly because it was difficult to convince Comcast's techs that the physical copper cable is probably not discriminating against IPv4 traffic. My experience w/ their business division is that the support agents have some light experience. My experience w/ their residential side is that the support agents have never seen a computer. The rollout to business was after the rollout to residential; I also filled out a form requesting one way back in the day when they were essentially polling for interest.
- cjcampbell 8y ago
  > This took several days to correct, mostly because it was difficult to convince Comcast's techs that the physical copper cable is probably not discriminating against IPv4 traffic. I'm torn between laughter and intense anguish. I'm afraid to even estimate how many days of my life have been spent honing my rhetorical skills to convince a support agent of similar points.

FireBeyond 8y ago

Right. Last I checked (business), with a static IPv4... IPv6 worked with one of the four available modems. If you had that one modem, you got dynamic IPv6, static wasn't supported. With your dynamic IPv6, you then had to modify your SLAAC(?) / DHCPv6 because of an incongruity between what the modem was saying, and what would work (I believe it said you had a /56, but you could only advertise a /64 internally). And so on.