Size of DHCP-PD change

Question

For a while now, IPv6 has been 'buggy' for my Comcast connection. For example, IPv6 websites like Facebook and LinkedIn loaded slowly, if at all. Today, I was finally able to do some debugging. And what I found was that somehow the prefix that my firewall received from the cable modem changed. I used to get: xxxx..:80f0:/60now I getxxxx:80c0:/59  note that both are within the same 'static' /56 assigned to my modem. So the IPs assigned by Comcast to the modem haven't changed. Great... larger prefix. but the end result was that the cable modem no longer routed the IPv6 addresses I used inside my network. To make things a bit more tricky to debug: The cable modem just dropped the packets (not sure outbound or returned). In the past, I at least got an ICMPv6 'egress error' to help me debug this. Couple questions:- Can Comcast provide any advance notice about configuration changes like this?- Why do the DHCP dance at all? I still haven't quite figured out how to failover between firewalls with IPv6 if I have to request a prefix first, and may not get a consistent prefix back. Works fine with IPv4 but not at all with IPv6 in the current setup.

flybynight · Accepted Answer

I got a call back from a network technician at Comcast (about a week after opening the ticket originally). What it comes down to is that Comcast can't control what the modem (which is Comcast provided/maintained) does with DHCPv6 to the user's firewall. The technician stated that IPv6 addresses are not "static" (you only pay for static IPv4, not IPv6), so you should just assume that they may change every so often without notice.

So in the end, you are probably better off turning off IPv6 on the gateway. Or if you still use IPv6, there is no advantage in having a business account with static IPs. You are better off using a consumer account (I think you still get an almost-static /60 in IPv6 prefix with that. so nothing really lost)

Comcast_JosephA · Answer

Hello, how are you? I hope your day is going well and my reply reaches you at a good time. I will be happy to take a closer look at your service and answer all your questions. Are you currently using a static IP address? If you can send a private message I can take a closer look at your modem and double-check. Are you able to include your name, service address, and account number (or phone number)?

flybynight · Answer

I sent a private message with additional details.

Comcast_Gabriel · Answer

Awesome! Thank you for your patience and for sending over a private message. We will continue in assisting you from there. Please let us know if you have any additional questions or concerns.

flybynight · Answer

Today, sadly close to the end of the business day, my modem rebooted without warning (disrupting a call I was on) and I got yet another IPv6 prefix, dropping IPv6 traffic again for me. Instead of renumbering, I took a different approach this time and just kept changing my firewalls DUID until I got the old prefix back 😕 . Less than ideal. Apparently my ticket with support is still open. This isn't exactly "business class" quality connectivity or support. Support stated that they did not trigger the modem reboot. So no idea what or who caused it, or who is at the wheel "managing" the network at Comcast. Sorry. Getting a bit frayed nerves here.

flybynight · Answer

Comcast_Joseph: I replied to your direct message, but just like my first direct message to you, it appears to be unread. Maybe some problem with the messaging system?

ndb217 · Answer

Were you able to resolve this? If so, what was the resolution. For my own curiosity, are you using static IPv4 addresses? If so, what comcast cable modem are you using?

CC_RobertC · Answer

Hi there! I'm so sorry for the delay. During this time we have a need for an increased support, but we are doing our very best to make sure we respond to you as soon as possible. Thanks so much for reaching out about an update on progress and resolution of your request. You've absolutely reached the right place, and are in good hands. I will own this Issue for you and ensure that I provide the best help I can today. All I need is your full name, account number (follow link https://comca.st/3hE94Hi, account number is at the top right)and address including city, state, and zip code exactly how it reflects on the bill, and I can help you with whatever questions or concerns you may have.

flybynight · Answer

Robert:

Thanks for your offer to help. One week into this ticket, it is nice to have someone "own" it now.

Couple problems:

When I tried to send you a direct message, I get an error: "You have reached the limit for number of private messages that you can send for now. Please try again later." (the little bit odd working of this message is from the system, not mine). Maybe because I already sent that information a few times to various Comcast_* accounts? I will certainly try again later.

Also, the link you included is for the persona account page, not the business account page. You are sure you are up to "own" this problem?

flybynight

Size of DHCP-PD change

flybynight

Comcast_JosephA

flybynight

Comcast_Gabriel

flybynight

flybynight

ndb217

CC_RobertC

flybynight