> If a link was partitioned when two hosts did DAD, and the network heals
> up, what happens? Is there any way to recover from the situation?
> Are the both nodes screwed until either interface is brought up and down,
> enabling DAD?
Yes, and you can't easily tell that you're hosed.
At some point in time we might have discussed having 3rd parties
doing address resolution detect when a multicast NS results in two
NAs containing different addresses and sound the alarm.
But I think the use fo proxy NAs (e.g. for mobile IP on the home link)
makes this type of 3rd party discovery tricky.
> Which brings me to an idea: some implementations (routers, usually) have
> knowledge of link status (cable is/is not plugged in, is broken etc.).
> For these, would it make sense to defer DAD until link goes up and keep
> the address tentative until then? If a lot of implementations did this,
> the consequences of broken linkcould be smaller. Nodes have no way of
> knowing if network was partitioned upstream, of course.
That only helps at the attachment to the link - doesn't help e.g. if
two Ethernet hubs/switches loose the link between them.
> Also, it could be possible to redo DAD after link status cycled, but this
> could add too much traffic to the network and might open a door for easier
> address stealing.
Sure, an implementation can do DAD once the link is up for links that
have a notion of being up vs. down.
But that doesn't help with internal partitions on the link.
Erik
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