IPv6 does not come back automatically after CM drops and reconnects IPv4 does



  • pfSense 2.1.5-RELEASE running on a Neatgear APU2, Motorola SB6141 CM Comcast subscriber.

    Comcast has been dropping my CM connection quite a bit lately, so I've only noticed this now: When the CM reconnects the IPv4 DHCP WAN connection is re-established, but the IPv6 DHCP is not. I can manually get around this easiest by going to "Interfaces -> WAN" and clicking "Save" to re-init the WAN connection. The DHCP6 settings are in the attached screenshot.

    If I reboot everything comes up ok too.

    Obviously I'd like IPv6 to recover automatically too, am I doing something wrong?

    ![Screen Shot 2014-09-09 at 4.49.02 PM.JPG](/public/imported_attachments/1/Screen Shot 2014-09-09 at 4.49.02 PM.JPG)
    ![Screen Shot 2014-09-09 at 4.49.02 PM.JPG_thumb](/public/imported_attachments/1/Screen Shot 2014-09-09 at 4.49.02 PM.JPG_thumb)



  • This is a well-known issue with pfSense; see e.g. this and this bug report. There's forum threads on this topic as well. The problem is that when the cable modem loses connectivity, it starts handing out DHCP leases from the 192.168.100.0/24 range, which causes pfSense to think connectivity exists; however, the cable modem does not advertise any IPv6 prefixes, and that causes pfSense to completely give up on IPv6 connectivity, even when the cable connection goes back up.





  • @razzfazz: Thank you for that. I guess my forum search-fu wasn't as good as I thought.

    So, it would seem the issue is that dhcpv6 should keep hammering away until told otherwise? In the meantime I think I'll try the hack of a switch between the WAN port and the CM. Since the route to the management IP (192.168.100.1) is going to go out the WAN port anyway (works even when the WAN is up) it shouldn't break anything and DHCP can then expire and be re-allocated as intended. IOW the downing of the WAN link is not always a DHCP (4 or 6) event. With the long lease times that Comcast seems to use this workaround may be better for me.

    BTW the first Bug report link is 404?



  • It doesn't have to keep trying if nothing changes; however, I don't think the current approach (die when no response) is the right one, either – at the very least, it should retry whenever there are any connectivity changes (e.g. in this particular case, when the IP on the WAN changes).



  • Does anybody know if this will be fixed in 2.2?
    I was searching to see if there was an open issue for this, but don't seem to be finding one.
    Issue 2878 mentioned in one of the links is long-closed.
    Like others here, after a long period of stability, Comcast seems to be resetting the modem on an obnoxiously regular basis and every time they do, I lose my IPv6 connectivity.
    I'm more than happy to help debug the problem.



  • I have a router running on time warner cable that does exactly the same thing.  Very annoying.

    I keep forgetting to switch that one to HE.  Maybe tomorrow…