DAD problem when a looped interface comes back up
Pekka Savola <pekkas@netcore.fi> Tue, 27 May 2008 06:34 UTC
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Date: Tue, 27 May 2008 09:34:08 +0300
From: Pekka Savola <pekkas@netcore.fi>
To: ipv6@ietf.org
Subject: DAD problem when a looped interface comes back up
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FYI, This issue, from cisco-nsp list, might be of interest here. When an interface is looped, it will fail DAD, and if the condition lasts long enough, you might not recover from it automatically. On Tue, 27 May 2008, Gert Doering wrote: > On Tue, May 27, 2008 at 03:00:26AM +0300, Hank Nussbacher wrote: >> When we did some line testing and did some loop testing on the link we got: >> %IPV6-4-DUPLICATE: Duplicate address FE80::215:2CFF:FE87:B240 on POS11/0/0 >> >> petach-tikva-gp# sho ipv6 int pos11/0/0 >> POS11/0/0 is up, line protocol is up >> IPv6 is stalled, link-local address is FE80::215:2CFF:FE87:B240 [DUP] > [..] > >> I know I can use "ipv6 nd dad attempts 5" but wanted to know whether I >> should open a TAC case for this. > > I have seen this as well, and it's especially annoying if it happens > as consequence of a link outage from the carrier (link going down, going > into "loop" state, then coming back to "up") - if you're unlucky, a short > glitch can kill your IPv6 on the line hard until you manually reset the > interface. > > The current behaviour is pretty much a direct consequence from the RFC > (DAD is mandatory), but I think that IOS could be a bit more smart about > it, like "restart DAD every 5 minutes" or "recognize a looped->up > transition on the interface, and then restart DAD". > > So - by all means, please open a TAC case. > > As a workaround, we have used "ipv6 nd dad attempts 5" on the specific > line that gave us headaches - so we've never pressed the issue with Cisco. > > gert > > > -- Pekka Savola "You each name yourselves king, yet the Netcore Oy kingdom bleeds." Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------