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Re: ndp -a stops for a while because of lo0

On Mon, Oct 22, 2012 at 09:29:11PM +0200, Lars Schotte wrote:
> On Mon, 22 Oct 2012 14:22:17 -0400
> Greg Troxel <> wrote: 
> > use '-n' to disable dns.  on my machine, 'ndp -a' is quick.
> well, that's right, i did not expect that it may be DNS that makes this
> all slower, with ndp -an it's fast to me as well.
> > It looks like lo0 has no MAC address, which makes sense.   It may or
> > may not be a bug that there is an NDP entry.
> OK!
> > That's a 'link local' address.  I think every interface is required to
> > have one, and there's no reason they have anything to do with MAC
> > addresses.
> Link Local would be ::1, or not???

No. Formally, that's not a link local address. Semantically, it's 
host-local. Link-local addresses are visible outside the machine,
but can't leave a specific logical link.

> But OK, I see the point that they need to have one with fe80::1 but if
> this is required for loopback is the question. Maybe a sysctl control
> could be made so that per default auto_linklocal would be disabled for
> loopback device(s) (lo/lo0).

You're trying to fix a problem that's not there at all. Whatever causes
your delay is caused by some name resolution on something else, I think.

My ndp -a (without -n) finishes with 10ms wallclock time, and resolves
all but the link-local addresses, be it from wm0, fwip0 or lo0.

Link-local addresses on all active links are required so that
diagnostic or infrastructural programs can operate on a link without
an a-priori-knowledge that it's supposed to be a loopback one.

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