/59 prefix delegation block changed...

you got it easy. I just had my modem upgraded and I got an entirely different /56 assignment. To make matters worse, every time the modem reboots I get a different /59 assignment to my firewall. There is no way to statically assign anything IPv6 inside of the modem's web interface so ipv6 is pretty broken in terms of being able to set anything statically. At least my old modem kept the same /59 assigned to my firewall the entire time I had it.

Hello and thank you for reaching out to us. I apologize for the delayed response time but thank you for sticking with us to address your questions and concerns! I am here to help! In order to get started can you please send me a private message with your full name and service address? To send a private message, click my name "ComcastDena", then click "send message".

I clicked your name but don't see a "send message" button. Please advise.

If I click the message button & type in your name, it doesn't work either:

@MikeAce , do you have a static /56 assigned as well?

@Comcast_Dena , Yes I do have that, but as per my screenshot it can't find you to send a message to.  If I type Comcast_D, it will  show me 3 or 4 other people I can send a message to, but not to you.  Maybe if you could send me a message I could just reply?

I've never actually received an official word from Comcast business that IPv6 assignments are truly static. When I got the new modem and I saw my delegated /56 had changed, the tier 3 tech had no idea about the intended behavior. It's very disappointing because I have a static IPv4 block that did transfer over

@MikeAce : My static IP block /56 shows under my static ips next to my static ipv4 ips.  Do you have static ipv4 ips?  If not it may not be static.

Yes I have a static /28 of IPv4

It should also show you a /56 next to your /28 in your account.  If a /56 doesn't show up, that is the issue.  You may have to ask them to assign you one so it stays static.  Might be dynamic otherwise. Maybe @Comcast_Dena can assist if that is the case.

Yeah it says I have a /56 delegated prefix and it stays the same with the modem. as soon as the modem was changed out though I got a different /56 and Tier 3 didnt have an answer

Wow, so Tier3 couldn't figure out why your /56 wasn't matching up with what they assigned you?  I'd hope they could fix that same as they fix static ipv4 blocks not routing to you...wow...

I'm having this same problem.  We have a static /56.. our system is configured to request a /59 (largest block have been able to pull).  This has been working for years with no issues.  Just 3 days ago this delegated prefix changed (different bits within our /56) requiring us to renumber all our systems, software, DNS...etc.

The problem is now that since then traffic stops passing on the newly delegated prefixes after about a day of uptime... This has happened twice so far over the past two days and we've had to renumber each time.  No idea how to wake up Comcast's systems to allow traffic to pass.  Previously for residential when this would happen you could just kick the DHCP and it would update Comcasts filter to allow traffic to pass again but here nothing seems to work anymore.

We can receive IPv6 packets yet all outgoing IPv6 packets on the delegated prefix are dropped after it leaves our WAN port to Comcast.  Ran a packet capture and can see the IPv6 packets going out of the WAN interface.  The /64 on our WAN interface works fine and we can ping out from it but everything on our production LAN network using the delegated prefix has no working IPv6 after a days time it stops working.  All of the packets are being dropped.

Modem has not been replaced and there have been no hardware changes on our end.    I don't know if firmware updates were recently pushed to the modem.

Delegated /59 prefix we had been assigned for years was ...:43e0:: then it went to ...:4340:: and finally ...:4300::.  First time it took a while to notice the LAN prefix had changed.

What I know is that after each change it works for about a day probably somewhat less.  Unsure exactly how long.  After this outgoing packets would be dropped.  This happened both times from 43e0 to 4340 and 4340 to 4300.  I don't know if both were exactly the same interval but it was about the same.

No idea what triggers changes.  For all I know it could have been automatic or triggered by rebooting CM or system or fiddling with DHCP trying to poke whatever is blocking traffic.  The last time it changed was on phone with a Comcast CSR.

@packeteater , @Comcast_Valerie , @Comcast_JamesH , @Comcast_Dena 

Just an hour or so ago, my ipv6 routing died.  I could make it to the cablemodem not past it.  I rebooted the cablemodem, played with the lease time, toggled DHCP and now my /59 I'm receiving went from c000::/59 and c040:/59.  My ipv6 behind the cablemodem is completely broken now unless I renumber all my servers.  THe last time this happened it took about 2 hours to renumber.  Further reboots have left me with c040 and can't get me back to c000 which is the base of my /59.

Can anyone suggest a fix?  How about just routing the entire /56 to an IP address I give support?  Is this doable?  Any other suggestions to keep the /59 from changing?  Any way we can manually add in static ipv6 routes to the cable modem reather than using dhcpv6-pd ?

I'm open to any/all suggestions.  In the meantime I've turned off ipv6 on my firewall requesting the PD as in the current state it is not functional.