Re: [v6ops] SLAAC renum: Problem Statement & Operational workarounds

Trevor Warwick <> Thu, 24 October 2019 09:59 UTC

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From: Trevor Warwick <>
Date: Thu, 24 Oct 2019 10:57:26 +0100
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Subject: Re: [v6ops] SLAAC renum: Problem Statement & Operational workarounds
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On Thu, 24 Oct 2019 at 09:18, Mark Smith <> wrote:

> I thought about this in the exact context of the scenario of this draft.
> Although the design of the broadband deployment I worked on always planned
> to give out stable prefixes, I worked through this scenario and realised
> that so many complex issues disappear if you provide stable prefixes.
> Fundamentally, if an ISP is selling an always on link to the same
> location, then the addressing should be as permanent as the link delivery
> location is.
If you're an ISP today, and using DHCPv6-PD to hand out IPv6 prefixes, what
are the possible scenarios if you don't try hard to keep the prefixes

- You could be running a closed environment where all customers are forced
to use your CPE, in which case you can make sure that your CPE has various
 hacks added to try to cope with prefix instability and avoid customer
hosts experiencing connectivity issues when prefixes change. Maybe you can
make this work well enough, and advanced customers who don't want to use
your CPE are just out of luck.

- If you're in an environment where customers can chose their own CPE, then
it seems almost guaranteed that there will be connectivity problems when
the prefix changes, because many CPE implementations don't handle this
situation at all. So you're then relying on hosts falling back seamlessly
to IPv4, in order to continue to have connectivity. In which case, I'd
wonder why you're bothering to provide an IPv6 service in the first place.

I do think this is an important problem that needs to be solved, for this
context and the others mentioned in the draft.