Re: [2.4 PATCH] bugfix: ARP respond on all devices

[Harley Stenzel <hstenzel@xxxxxxxxxx>]

David S. Miller wrote:
> On Tue, 19 Aug 2003 19:05:13 +0100
> Richard Underwood <richard@xxxxxxxxxxxxxxxxx> wrote:
>
> >         The ARP request represents all FUTURE
> > packets being sent out that interface, not just the one single packet that
> > happened to kick of this ARP request.
>
> That's RIGHT!  And by your own argument the source address
> in the ARP request IS IRRELEVANT and is to be ignored!

The source address in the ARP request is not irrelevant, because a 
broadcast arp request causes all recipients of that broadcast request to 
update their arp cache entry (if they have a cache entry for that IP) 
for the IP specified in the source with the MAC specified in the request.

So, in an environment where a single address is aliased in multiple 
places, such as tunnel endpoints and loopback aliases, and in 
multi-homed same-segment configs, it is unpredictable asto which IP will 
be bound to which MAC for every machine (or arp cache) on the network.

--Harley