> 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.
this is a flaw in the way DAD was designed. one solution could be to add a nonce option to ND. another would be to turn DAD off. /ot > 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 > -------------------------------------------------------------------- > -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
