Re: [Qemu-devel] Intermittent e1000 failure on qemu-kvm 1.0

[Stefan Hajnoczi]

On Mon, Apr 02, 2012 at 04:37:23PM +0100, Chris Webb wrote:
> We initially saw a problem after an upgrade from 0.15.x to 1.0.

Perhaps git-bisect(1) can help you track down the change that introduced
this between 0.15 and 1.0.

> Once I've got a guest with broken networking, the network stays down even if
> I do things like 'ip link set eth0 down; sleep 5; ip link set eth0 up'.
> Killing and restarting the same VM, it runs fine next time.

It sounds like this is not the issue, but are you sure the bridge has
forwarding delay set to 0 or Spanning Tree Protocol disabled?  With STP
enabled no traffic will be forwarded by the bridge for a configured
timeout, and depending on the timing of your VM bootup you could see
weird things.  You can check with brctl showstp br0.

Stefan