[c-nsp] IPv6 duplicate address

[Steve Bertrand]

>> In:
>> http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122t/
>> 122t2/ipv6/ftipv6c.htm#10168
>> Cisco states "An interface returning to administratively "up" restarts
>> duplicate address detection for all of the unicast IPv6 addresses on the
>> interface."  It would appear if an interface goes from up (looped) to up
>> (non-looped), IOS does not check for dup addresses and the interface stays
>> stalled.  Is this how it should be or is this an IOS bug (12.2(18)SXF11)?
>>
>> I know I can use "ipv6 nd dad attempts 5" but wanted to know whether I
>> should open a TAC case for this.
>>
> 
> Why not disable it entirely?  If you have a POS interface connected to
> another one directly, couldn't you set it to 0?


Hmmm. I don't think that this is the OP's point.

If I'm not misunderstanding the problem, could this be an issue that 
either was missed in the framework of RFC 4861, or perhaps an 
implementation issue?

I would think/hope that DAD under Neighbor Discovery would sort this 
out, and not permanently stall an interface. If anything, shouldn't the 
on-link interface expire the entry and then retry?

What does the Neighbor Discovery neighbor cache show when this happens? 
(I don't know how to check this on a Cisco device, only on FreeBSD).

I don't think this is how it should be, but perhaps I understand wrong. 
I would have thought that going from up (looped) to up (non-looped) or 
vise-versa (or up-down-up in general) would provide a ND cache reset, at 
least for the addresses attached to the on-link interface(s).

Steve