On Mon, Nov 13, 2000 at 11:25:43AM +0900, itojun@iijlab.net wrote:
> 
> >> 	"server" is not seeing the neighbor solicitation packet from "drifter",
> >> 	and that is the very reason DAD is not working.
> >Yes, I agree. But did you see that the server *does* see the pings
> >from drifter to ff02::1:ff00:2? Wouldn't that mean that mutlicast
> >through the switch is ok?
> 
> 	this could mean that the outgoing interface on "drifter" is not
> 	initialized properly and cannot generate packets right after the
> 	initialization, or whatever.  it basically is a timing issue - there
> 	are some delay factor implemented in the kernel code, but for some
> 	of the drivers/ethernet cards they are not enough.

This sysctl solves my problems, so it seems indeed timing related:

	sysctl -w net.inet6.ip6.dad_count=3

Setting it to three makes duplicate detection work between tlp0 and
ex0, but not for tlp0 and ep0 (latter on slow i486 laptop). Setting it
to 5, makes duplicate detection work for the latter to.

Would it be a good idea to increase the default of 1 to a somewhat
higher value? This makes booting slower, but is a bit more
conservative. Otherwise, would this be appropriate to add as comment
to the man-pages of the different drivers or document properly
elsewhere (like in /etc/rc.conf?). Properly documenting this would be
a good short-term solution to this problem with these cards/drivers,
which can more easily be added to 1.5 than code-changes.

Feico.