Hi, Bill, Thanks for the feedback! In-line.... On 10/3/19 13:54, William Herrin wrote:
On Fri, Mar 8, 2019 at 3:32 AM Fernando Gont <fgont@si6networks.com <mailto:fgont@si6networks.com>> wrote:
If you follow the 6man working group of the IETF you may have seen a bunch of emails on this topic, on a thread resulting from an IETF Internet-Draft we published with Jan Žorž about "Reaction of Stateless Address Autoconfiguration (SLAAC) to Renumbering Events" (Available at: https://github.com/fgont/draft-slaac-renum/raw/master/draft-gont-6man-slaac-... )
Hi Fernando,
I'm a little confused here. I can certainly see why the default timeout of 30 days is a problem, but doesn't the host lose the route from the RA sooner?
Which route? Configuration of addresses is mostly a different business than acquiring routes. SO, in the typical scenario where the CPE crashes and reboots, hosts will even have a default route -- advertised by the router that crashed and rebooted. If you are referring to the "on-link" route -- i.e., the route introduced because the Prefix Information Option had the "L" bit set -- then I don't think there's anything in the standard to actually grabage-collect such routes.
Why would an IPv6 host originate connections from an address for which it has no corresponding route? Isn't that broken source address selection?
Please see above. The mechanism we specified in Section 5.1.3 of our draft tries to do exactly that: Try to detect when a previously-advertised prefix has become stale... and when it's inferred to be stale, just remove all the corresponding information. Regarding fixing this issue with source address selection: some have suggested that his should be addressed in source address selection. However, there are a number of problems with this. If you prioritize addresses from the prefix that was last advertised, then source addresses are guaranteed to flap -- and in the cause of multi-prefix networks, this would become a troubleshooting nightmare. Secondly, if you don't remove the on-link route for the stale-prefix, then packets meant to the new "owners" of that prefix will be assumed to be on-link, and hence communication will fail. This should probably be an indication that the solution is not to avoid using the stale information, but rather discarding it in a timelier manner. Please do let me know if I've missed anything. Thanks! Cheers, -- Fernando Gont SI6 Networks e-mail: fgont@si6networks.com PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492