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

Fernando Gont <> Fri, 25 October 2019 18:11 UTC

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To: Ted Lemon <>
Cc: Ole Troan <>, v6ops list <>
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From: Fernando Gont <>
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Date: Fri, 25 Oct 2019 15:10:55 -0300
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Subject: Re: [v6ops] SLAAC renum: Problem Statement & Operational workarounds
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On 25/10/19 14:59, Ted Lemon wrote:
> On Oct 25, 2019, at 1:52 PM, Fernando Gont <
> <>> wrote:
>> The "flash renumbering" could also happen if the CPE was trying to kind
>> of the right thing, the ISP does not employ stable prefixes, and the CPE
>> happens to crash and reboot. Some CPEs also reportedly do a "release"
>> when rebooted.
> That’s probably a bug.   If the CPE has a valid lease, and the prefix is
> still working, it should continue to advertise it until its valid
> lifetime expires. 

Normally CPEs keep no state in stable storage about that.

> The ISP DHCP server should be giving the router two
> prefixes if it’s being renumbered: the preferred one, and the one that’s
> still valid but not preferred anymore.

The reality is that, we have all sort of things in the echosystem. So if
the network is to be robust, while we can and do improvements were
possible/needed. That said, there should be smarts on the hosts to cope
with these scenarios gracefully (hope for the best, plan for the worst).

Fernando Gont
SI6 Networks
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