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Comcast IPv6 Not Working

Contributor

Comcast IPv6 Not Working

IPv6 abruptly stopped working on my Xfinity Internet connection Monday 01/15/2018.  Xfinity is no longer assigning an IPv6 address to my router or /64 prefix delegation for my local network.  The Comcast IPv6 Test fails (http://test-ipv6.comcast.net), and I cannot browse http://ipv6.whatismyv6.com/ (see screenshots below).

 

I have a Zoom 5370 modem which is on Xfinity's list of approved modems according to the link below.  I also have a TP-Link Archer C1200 router.  I have had this combination since early 2016 and never had any IPv6 problems before.  I connected my laptop directly to the modem, and Xfinity also does not assign an IPv6 address to my latptop.  I have also power cycled my modem and router multiple times to no avail.  I also contacted Xfinity support via chat, and they took me through all the basic troubleshooting steps and also reset my modem to no avail.  I am a network engineer, and I need IPv6 for work.  Can someone please help?

 

https://mydeviceinfo.xfinity.com/device/zoomtelephonics-5370-458

 

comcast ipv6 test.pngwhatismyv6.pngrouter.png


Accepted Solutions
Contributor

Re: Comcast Not Assigning IPv6 to my Router

My IPv6 issues have been completely resolved.  The problem turned out to be a recent firmware upgrade on my TP-Link Archer C1200 router which I have since replaced with an ASUS RT-AC66U_B1 router.  IPv6 now works reliably, and I always get the same IPv6 LAN prefix delegation after multiple reboots.  The ASUS RT-AC66U_B1 also supports IPv6 firewall rules, and with stable LAN prefix delegation, I can finally enable IPv6 access for my personal (non-business) web server.  The TP-Link Archer C1200 also seems to have been the problem with receiving random IPv6 LAN prefix-delegation networks after reboots and power failures.


All Replies
Contributor

Comcast Not Assigning IPv6 to my Router

Comcast is no longer assigning an IPv6 address to my router of a /64 prefix delegation for my local network.  IPv6 abruptly stopped working on Monday 01/15/2018.  It started working again a few days later out of the blue.  Then it stopped working again Monday 01/23/2018.  The Comcast IPv6 Test fails (http://test-ipv6.comcast.net), and I cannot browse http://ipv6.whatismyv6.com/ (see screenshots below).

 

I have a Zoom 5370 modem which is on Xfinity's list of approved modems according to the link below.  I also have a TP-Link Archer C1200 router.  I have had this combination since early 2016 and never had any IPv6 problems before.  I connected my laptop directly to the modem, and Comcast also does not assign an IPv6 address to my latptop.  I have also power cycled my modem and router multiple times to no avail.  I also contacted Comcast support, and they took me through all the basic troubleshooting steps and also reset my modem to no avail.  I need IPv6 for work.  Can someone please help?

 

https://mydeviceinfo.xfinity.com/device/zoomtelephonics-5370-458

 

comcast ipv6 test.pngwhat is my ipv6.pngrouter.png

Contributor

Can I get a static IPv6 /64 for my local network

Is it possible for Comcast to assign a static IPv6 /64 subnet for my home local area network (LAN) rather than assign it via DHCPv6 prefix delegation?  My DHCPv6 assigned /64 prefix delegation changes frequently upon router reboot or power failure, and I constantly have to restart my devices and re-IP those that have static IPv6 assignments. 

 

DHCPv6 is fine for my router's WAN IPv6 assignment.  I am only asking for static /64 subnet for my home LAN so it does not change.  For example, my home LAN IPv4 network is 192.168.100.0/24, and it never changes.  Of course it gets NATed by the router for Internet access, but it never changes, and I can assign static IPs to my printers, TVs, etc and never have to worry about re-IP'ing them.

 

On my router, I would disable prefix delegation and manually enter the static IPv6 /64 network that Comcast assigns for my local network as shown below as an example.

 

Untitled.png

Regular Contributor

Re: Can I get a static IPv6 /64 for my local network

I don't think anything changed but, anything is possible.  IPv6 is working for me w/ MB8600 / Netgear R7800 / Intel 9260.  It should hand off IPv6 from the modem to the router and your router gives you your local IPv6 address. 

 

Have you tried doing a hard reset on both devices?

Sounds like something is hanging along the way from CC to your LAN and it could be either device.  AFAIK CC doesn't assign static IPv6 other than potentially on Business accounts.

Contributor

Re: Can I get a static IPv6 /64 for my local network

IPv6 works, but the /64 prefix that Comcast assigns to my router which in turns assigns to my local network changes if my router reboots or if power fails.  So my IPv6 prefix could be 2001EAD:BEEF:BAD::, and after reboot it could change to 2001:BAD:BEEFEAD:: meaning I have to change all my devices that have static IPv6 assignments. And some devices with dynamic IPv6 assignments do not automaticaly update, and I have to reboot them to get them to update to the new prefix.  I assign static IPv6 to my printer and other devices becasuse I want them to be static.  My problem is the equivalent of my IPv4 changing from 192.168.100.x to something like 172.16.10.x.

Regular Contributor

Re: Can I get a static IPv6 /64 for my local network

You have 2 options... Gig Pro $300/mo or Business 

 

I would probably reach out to the business group in hopes they might have a solution that would also work on a Residential account. 

 

So, initially you said v6 wasn't working and now reporting it is working?  

 

So, why the hassle of making things static on both v4/6?  Why not go static on v4 since you have complete control over that and then let v6 go auto and use some sort of dyndns solution for lookup / translation? 

 

Since you're using it for work the upgrade to pro/biz class shouldn't be that big of an issue for them to reimburse for if it's a vital need.

Contributor

Re: Can I get a static IPv6 /64 for my local network

V6 is still not working at the moment.  These posts were supposed separate but some moderator (EG) comibned them because he incorrectly thinks they are related.  I was asking about the static /64 in anticipation that V6 service would eventually be fixed.

 

Right now I am consdiering switching providers.  AT&T recently installed AT&T fiber in my neighborhood.  Why would I pay Comcast more money for business service when my current service is broken with no end in sight?

Contributor

Re: Can I get a static IPv6 /64 for my local network

Also I think you are confusing what I mean by static.  My home IPv4 subnet (not static IPs) is static which means it is always 192.168.100.0/24 and never changes through a router reboot or power failure.  My router uses DHCP to assign 192.168.100.x IPv4 addresses to all of my devices.

 

All I want is the same for IPv6.  I want a static IPv6 subnet (not static IPs) that never changes.  For example, I want Comcast to assign prefix delegation 2001:AAAA:AAAA:AAAA::/64 as my local subnet every time my router reboots or if my power fails.  In fact, this /64 subnet assignment should be tied to my router MAC which never changes.  But for some reason, Comcast assigns a different IPv6 subnet after a reboot or power failure.  Again talking about static subnets and not static IP addresses.

 

For example, Comcast assigns an IPv6 prefix delegation of 2001:AAAA:AAAA:AAAA::/64 for my local network. My router uses DHCPv6 to assign 2001:AAAA:AAAA:AAAA::x IPv6 addresses to all my devices.  Then I reboot my router or there is a power failure, and Comcast assigns a different IPv6 prefix delegation such as 2001:FFFF:FFFF:FFFF::/64 for my local network. Going forward, my router assigns 2001:FFFF:FFFF:FFFF::x IPv6 addresses, but all my devices still have 2001:AAAA:AAAA:AAAA::x IPv6 addresses.  They do not know the subnet changed or to send a DHCPv6 broadcast request to get an updated 2001:FFFF:FFFF:FFFF::x IPv6 address.  I have to rebboot or disconnect all my devices from the network and reconnect them to force them to request a new IPv6 address.

 

The IPv4 analogy is if I changed the 192.168.100.0/24 subnet on the router to 172.16.100.0/24.  Going forward the router assigns 172.16.100.x IP addresses, but all my devices still have 192.168.100.x IP addresses.  They do not know the subnet changed or to send a DHCP broadcast request to get an updated 172.16.100.x IPv4 address.

 

The difference between IPv4 and IPv6 is that the user controls their local IPv4 subnet, i.e. 192.168.100.0/24 or 172.16.100.0/24, but Comcast controls the user's local IPv6 subnet, and it constantly changes which should not happen if the router MAC is the same.  They way IPv6 prefix delegation for local subnet is supposed to work is that the provider should assign the same /64 prefix delegation for the user's local subnet as long as the router MAC address does not change.  Upgrading or replacing a router will cause the router MAC to change in which case Comcast should indeed assign a different /64 prefix delegation for the local subnet.

 

Devices running dual stack, i.e. IPv4 and IPv6, will use IPv6 first by default.  Devices with IPv6 addresses, even if they are wrong, will not be able to access the Internet until the IPv6 addresses are corrected or IPv6 is disabled.

 

I am strictly talking about a static IPv6 prefix delegation for my local subnet.  I am not talking about a static IPv6 for my router's WAN port.  I expect my router's WAN IPv6 to change regularly on consumer service, and I have no problem with that at all because there is no such thing as NAT or port foward for IPv6.

 

If I were hosting an IPv6 web server, I should be able to make a static DNS AAAA record for my web server's IPv6 address which should never change because it comes from the local subnet prefix delegation which should be tied to my router MAC address.  Internet users would access my web server's IPv6 address directly whereas with IPv4 Internet users would access my router's WAN IPv4 address that NATs and port forwards to the private 192.168.100.x IPv4 address.  There is no concept of this in IPv6.

 

All IPv6 addresses are routable on the Internet.  There is no concept of private subnets, i.e. 10.0.0.0/8, 172.16.0.0/20, or 192.168.0.0/16, or NAT.  The router's firewall would only need to be configured to allow HTTP(S) traffic to my web server's IPv6 address on the /64 prefix delegated to my local subnet.

 

Regular Contributor

Re: Can I get a static IPv6 /64 for my local network

It's all really a moot issue unless something changes on the CC side where the v6 IP's start getting assigned like v4 and are bound to the MAC.  In the past my v4 on the modem was pretty sticky but, recently it's been changing on a whim as well even w/o a reboot or change being made.  As for devices running v6 they should pick up changes just like they would on v4 if the router gets rebooted or something else changes.  If they don't then there's an issue with the configuration on your router.  

 

As to ATT.... can't speak on that one, never gotten close enough to qualifying for gig with them.  Not truly having the option to try them out when their map says they have someone connected 2 blocks or less away <Edited for violating forum guidelines: "Inflammatory">

Authorized Vendor

Re: Can I get a static IPv6 /64 for my local network

Comcast doesnt do static IPv6 Prefixes what they do is an extended lease (reserve) for business customers..  Now as for your issue your IPv6 prefix shouldnt be changing each time you reboot your router, that is a broken router..  As long as your router is online for the renew all should be good...

 

Since we started IPv6 back in oh 2013 I think my prefix has changed about 6 times and that was due to IP address re-allocation not much any one can do about that..  I have had the same /60 block for over a year and half now I would say.. 

 

Bottom line if you need more of a reserve prefix then you would need to go to a business account..

-------------------------------------
Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Authorized Vendor

Re: Comcast Not Assigning IPv6 to my Router

Oh one more thing I have never tested or worked with a TP-Link Archer C1200 router..  If you send me your CM-MAC via PM I could check on one thing..  Some router vendors would reassign the DUID to each interface every time the device rebooted but I was thinking everyone fixed that back in 2015 but I could be wrong..  I could check the DUID for you before and after the reboot if you wanted..

-------------------------------------
Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Contributor

Re: Comcast Not Assigning IPv6 to my Router

My IPv6 issues have been completely resolved.  The problem turned out to be a recent firmware upgrade on my TP-Link Archer C1200 router which I have since replaced with an ASUS RT-AC66U_B1 router.  IPv6 now works reliably, and I always get the same IPv6 LAN prefix delegation after multiple reboots.  The ASUS RT-AC66U_B1 also supports IPv6 firewall rules, and with stable LAN prefix delegation, I can finally enable IPv6 access for my personal (non-business) web server.  The TP-Link Archer C1200 also seems to have been the problem with receiving random IPv6 LAN prefix-delegation networks after reboots and power failures.