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

To: "David S. Miller" <davem@xxxxxxxxxx>
Subject: Re: [2.4 PATCH] bugfix: ARP respond on all devices
From: Harley Stenzel <hstenzel@xxxxxxxxxx>
Date: Wed, 20 Aug 2003 08:52:09 -0400
Cc: Richard Underwood <richard@xxxxxxxxxxxxxxxxx>, skraw@xxxxxxxxxx, willy@xxxxxxxxx, alan@xxxxxxxxxxxxxxxxxxx, carlosev@xxxxxxxxxxxx, lamont@xxxxxxxxxxxxxxxx, davidsen@xxxxxxx, bloemsaa@xxxxxxxxx, marcelo@xxxxxxxxxxxxxxxx, netdev@xxxxxxxxxxx, linux-net@xxxxxxxxxxxxxxx, layes@xxxxxxxxx, torvalds@xxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
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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.


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