[lacnog] Articulo: Understanding why IPv6 renumbering problems occur

Fernando Gont fgont en si6networks.com
Lun Sep 16 07:16:11 -03 2019

On 15/9/19 18:48, Fernando Frediani wrote:
> Hello Fernando
> Thanks for sharing your article.
> In fact this issue is quiet common and annoying in many situations and
> must be addressed.

If you can, please comment on v6ops. Your input is really needed to make

> The first point to look at is for what reason ISPs would change/renew
> the DHCPv6-PD in use in a active connection, even after a long time. I
> understand it happens upon disconnection/re-connection but not in a
> active connection which is something that perhaps can be eliminated too.

Please see our draft. A number of scenarios are described.

> The point about ISPs deliver static prefixes I personally quiet like
> that and prefer to employ that as much as possible, but in the other
> hand I recognize there are a few challenges as how to properly aggregate
> these prefixes in a multi-BRAS environment as also the lack of a
> workable Delegated-IPv6-Prefix RADIUS Attribute on some BRAS or this
> functionality in some ERP/CRM Systems.
> I also don't really take that stable prefixes is a big issue in the
> point of view, but cannot ignore the concerns of some that see the
> implications in privacy.
> The point about the router recording DHCPv6-PD in stable storage not
> sure if will always solve the problem because it is likely then when the
> router is rebooted and re-connects to ISP it may receive a new prefix. 

The point is that if it has recorded the previously-leased prefixes, it
can send RAs with appropriate lifetime values to deprecate the stale

> I seems to me it would be more productive if somehow SLAAC could, one it
> is aware there was a prefix change to send a broadcast message with some
> kind of flag which devices should understand and fully refresh their
> IPv6 addresses immediately.

Well, an RA with proper lifetimes could, to some extent, achieve that.
But I believe for robustness-sake the smarts should be on  the hosts, as
opposed to the network.


Fernando Gont
SI6 Networks
e-mail: fgont en si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492

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