[GRLUG] Comcast dual stack IPV6 spotted in Muskegon

[Eric Yagerlener]

I'd have to agree with your assessment.   I've ran IPV6 with he.net
tunnelbroker for years and after 24 hours of playing with Comcast's
native IPV6, the kludgyness of Comcast's DHCPv6 is readily apparent.
Comcast's implementation isn't really respecting the promised lifetime
of the prefix it is handing out.   Should your cable modem reset for
any reason, ie a T4 timeout, it appears the lease will be silently
cancelled by the CMTS and the DHCPv6 client will be none the wiser and
the IPV6 connection will be dead.  There are tons of complaints and
bug reports out there about Comcast's IPV6 prefix delegations failing
to renew when it naturally expires or whenever the modem resets
causing IPV6 to drop.

If I get the time, I'll have to get a linux box with 2 NICS and do the
debugging on why comcast's prefixes delegations get terminated early.
In the meantime, it's back to IPV4 and tunnelbroker.   At least with
tunnelbroker your IPV6 prefix is set in stone, with Comcast, it will
change on a whim.   I thought the reasoning behind IPV6 is that
addresses won't by scarce.  I don't quite understand why Comcast isn't
using the same sticky persistence as they are when handing out V4
addresses.

On Sun, Nov 24, 2013 at 8:54 PM, Adam Tauno Williams
<awilliam at whitemice.org> wrote:
> On Sun, 2013-11-24 at 15:34 -0500, Mike Williams wrote:
>> What's a PD in this context?
>
> Prefix Delegation
>
> It has to do with setting the IPv6 [sort of] equivalent of the subnet
> mask for the router's LAN.
>
> For whatever reason DHCP is one area where IPv6 is really hacked up
> [IMHO].  They had the opportunity to redesign/fix auto-discovery &
> assignment but made a total hatchet job out of it.  So you have the
> elegant Router Announcement scheme but end up having to use DHCP with a
> bunch of extensions all over again.
>
> IPv6 is simply a *better* protocol than IPv4, and strips away decades of
> accumulated hacks.  But the DHCP... ugh, it is as sucky as IPv4.
>
> In its defense IPv6 is intended to support a *much* larger network than
> IPv4, so some of this is inevitable - but why you need DHCP on top of RA
> and autoconfig.  I dunno, it feels kludgy.  Why can't additional
> attributes just be encoded in the RA for a specific interface... ?
> Perhaps the need for the upper tier router to retain a state/assignment
> is the reason?
>
>> You'll need a DOCSIS 3.0 modem a router that supports both IPV6 and
>> DHCPV6-PD for it to work with Comcast. DD-WRT does not unless you
>> already have a version that supports IPV6 and hack in some packages
>> from OpenWRT to provide a dhcp client for IPV6.  DD-WRT does not
>> support ip6tables at all.
>
> --
> Adam Tauno Williams <mailto:awilliam at whitemice.org> GPG D95ED383
> Systems Administrator, Python Developer, LPI / NCLA
>
> _______________________________________________
> grlug mailing list
> grlug at grlug.org
> http://shinobu.grlug.org/cgi-bin/mailman/listinfo/grlug