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

From: Harley Stenzel <[email-masked]>
Date: Wed, 20 Aug 2003 08:52:09 -0400

David S. Miller wrote:
> On Tue, 19 Aug 2003 19:05:13 +0100
> Richard Underwood <[email-masked]> 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