[ovs-discuss] Openswitch VM to VM traffic switching

Todd Deshane deshantm at gmail.com
Thu May 13 20:25:52 UTC 2010

Hi Praveen,

Some comments inline.

On Thu, May 13, 2010 at 4:09 PM, Praveen Reguraman <preguraman at gmail.com> wrote:
> I tried your script and still ran into
> the same issue. But I think libvirt also uses a similar way of trying to
> bring the interface up and I had a problem in the creation of the VM since
> it was failing on TAP/TUN interface.

Last I checked libvirt didn't have support for passing a custom
qemu-ifup script.

>Turns out that it started working fine
> when I installed it in bridge compatible mode and used the brctl commands.
> May be the br_compat.ko brought in the TUN/TAP drivers for the kernel, which
> was probably not there. I had tried 'modprobe tun' and had a fatal error
> saying 'tun not found'. However, I learned that with Ubuntu Lucid Lynx, TUN
> module is built into the kernel. Somehow, the whole thing was confusing to
> me when it worked.
> Should it be that Openvswitch is always in br_compat mode?

The bridge compatibility mode is only for backwards compatibility.

> Or Could I use
> some kind of fake bridge and work this around?

It is possible to ovs switches (bridges) to work with KVM, but maybe
it is still non-obvious.

I'll make an attempt today or tomorrow and try to post a quick howto.


Todd Deshane

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