> On Wed, 29 Sep 1999, Christopher McCrory wrote:
>
> > John Fulmer wrote:
> > >
> > > The way I've seen this done (on BSDI boxen, I think) is that the
> > > system does an arp for it's own IP address before/as the interface is
> > > brought up. It it gets a response, it assumes that there is another
> > > box out there with the same IP address (not a BAD assumption).
> >
> > This IIRC is a gratuitous arp. In the kernel source I have seen
...
> no a gratuttous arp is a broadcast ARP response, telling eveyone who you
> are before they ask. arping to see if someone else has your address is a
> different ballgame.
Well, actually the original comment _does_ describe a gratuitous ARP, which
is defined as an ARP request sent for your own protocol address. All ARP
requests are broadcast. There are no responses to a gratuitous ARP, unless
there is an IP conflict. However, you're right in that the gratuitous ARP
doesn't itself have anything to do with address conflict detection. That
would be an additional (rather simple) step. Gratuitous ARP's alone are
handy for hot-swapping routers or NIC's.
-bp
-- # bryan at terran dot org # http://www.terran.org/~bryan
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