ISP DHCPv6 and /48

George, Wes wesley.george at twcable.com
Fri Jul 10 13:21:54 UTC 2015


On 7/10/15, 6:34 AM, "NANOG on behalf of Baldur Norddahl"
<nanog-bounces at nanog.org on behalf of baldur.norddahl at gmail.com> wrote:


>Perhaps the problem is that DHCPv6-PD is not intelligent enough. Yes there
>is a provision such that the user CPE could give a hint of how much space
>is want, but no, it doesn't work.
WG] Sorry, [citation needed]. We are using DHCPv6-PD that listens for and
responds properly to hints in production for millions of customers. Many
of the cheap plastic routers are even smart enough to stand up their own
DHCPv6 server so that they can do PD to give out /64s to subtended devices
or split out the /56 or /60 that they were given to their WAN, LAN, and
Guestnet so that each has its own subnet. Now you may have to specify a
list of devices that properly support PD such that you know they will work
with this configuration of multiple routers behind a switch, but requiring
your customers to use a device that supports your implementation of a
feature that they want isn't really that much of an imposition on them.
You wouldn't blame the protocol when IPv6 doesn't work for your customers
who use a device that doesn't support IPv6, would you?

>The user CPE does not understand this
>issue either and has no information that could make it the smart place to
>do the decision. Plus which of the multiple CPEs would be in control?
WG] IETF Homenet WG is currently chewing on the problem of multiple CPEs
in an unmanaged environment. It's not an easy problem if you have to
design it so that it works automagically no matter how strangely it's
connected together. You may want to check it out:
http://datatracker.ietf.org/wg/homenet/charter/

>
>Maybe if the CPEs would go back and ask for more address space, if what
>they initially got ran out. But DHCPv6-PD does not really have a way to do
>that. In any case no CPE implements any such thing.

WG] also not exactly true. No, most CPE won't do it automatically, but
DHCPv6 can do it. Release existing prefix, request new prefix with bigger
hint. Depending on DHCP server policy, you might even be able to do it in
the opposite order (make before break) since you can have multiple
prefixes. My hunch is that on most residential broadband setups, it's not
likely to be hitless, and most cheap plastic routers can probably only do
it via a reboot after you reconfigure it to ask for more space in the
hint, but it's doable. See above recommendation for homenet if you want it
to be automatic.


Thanks,

Wes George

Anything below this line has been added by my company’s mail server, I
have no control over it.
-----------



This E-mail and any of its attachments may contain Time Warner Cable proprietary information, which is privileged, confidential, or subject to copyright belonging to Time Warner Cable. This E-mail is intended solely for the use of the individual or entity to which it is addressed. If you are not the intended recipient of this E-mail, you are hereby notified that any dissemination, distribution, copying, or action taken in relation to the contents of and attachments to this E-mail is strictly prohibited and may be unlawful. If you have received this E-mail in error, please notify the sender immediately and permanently delete the original and any copy of this E-mail and any printout.


More information about the NANOG mailing list