[ipv6hackers] DAD and Link-Local

[Owen DeLong]

I believe you are correct, but, it is not the first RFC to be commonly broken.

In terms of Point to Point links, I believe that BCP dictates disabling DAD so as to avoid
having a meaningless accidental address duplication causing a shutdown of the link
to transit traffic.

Owen

On Jul 14, 2012, at 1:05 AM, Marc Heuse wrote:

> dont nail me to that, but I remember that the rfc says that DAD has to
> be performed everytime, for manual, SLAAC and dhcp address configuration.
> 
> they can all conflict, my chance or by mistake.
> 
> the chances of conflict are slim, but ipv6 tries not to work 99.99% of
> the time but 100% :-)
> 
> 
> Am 13.07.2012 20:35, schrieb Owen DeLong:
>> DAD can be disabled if you are sure that there is no chance of collision.
>> 
>> With randomly chosen IID, you're not sure, but it's highly unlikely.
>> 
>> With MAC-based IID, you can check once and be sure until the hardware changes.
>> 
>> On a point-to-point link disabling DAD is probably harmless even if there is a collision.
>> 
>> Owen
>> 
>> On Jul 13, 2012, at 6:49 AM, <daniel.bartram at bt.com> <daniel.bartram at bt.com> wrote:
>> 
>>> All,
>>> 
>>> After some advice...
>>> 
>>> Aware that DAD is performed on link-local as well as global addresses to ensure uniqueness, but if the link-local is a randomly generated value, or even the IID for that matter, on a P2P link using only link-local addresses, what are the chances of those addresses ever matching? In which case, can DAD be disabled?
>>> 
>>> Dan.
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>> 
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> 
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