>> Short of sounding a bit naive, could someone explain to me exactly what
>> DAD is?  I've been testing my new VAX out, and I notice that it does a
>> "DAD" search on the ethernet controller, ze0...
>duplicate address detection, IIRC

	That is correct, DAD is for duplicate address detection.
	RFC2462 5.4.  when we assign an IPv6 interface address, we try to
	make sure no other machine is using it on the same link by sending
	probe packet like this. (the example is for probing duplicate for
	"3ffe::1")
	everyone with "3ffe::1" listens to multicast address "ff02::1:ff00:1",
	so if there's other guy, he will notice of duplicate and complain.

itojun


01:39:18.213283 :: > ff02::1:ff00:1: icmp6: neighbor sol: who has 3ffe::1 (len 24, hlim 255)