From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] net packet storms with multiple NICs
Date: Wed, 11 Nov 2009 01:19:18 +0000
Message-ID: <200911110119.18839.paul@codesourcery.com>
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Cc: Michael Tokarev <mjt@tls.msk.ru>, KVM list <kvm@vger.kernel.org>
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> I immediately reproduced the problem locally.  It turns out that
> kvm reflects packets coming from one guest NIC on another guest
> NIC, and since both are connected to the same bridge we're getting
> endless packet storm.  To a level when kvm process becomes 100%
> busy and does not respond to anything but `kill -9'.

You created a network loop. It is working exactly as expected.
Create the same topology with a physical network hub and a pair of NICs and 
you'll get the same end result.

Paul