[libvirt-users] Connecting a VM to an existing OVS bridge

[Amir Sela]

On Fri, 10 Jan 2020 at 19:36, Laine Stump <laine at redhat.com> wrote:
>
> On 1/4/20 4:48 AM, Amir Sela wrote:
> > Hi,
> > I have an existing OVS bridge, that I can see in ovs-vsctl and use
> > for other purposes.
>
> Does the bridge show up when you run "ovs-vsctl list-br"? Both OVS
> bridges I have on my system are seen in that list. I created them both
> with "ovs-vsctl add-br BLAH". How did you create your bridges?
>
> >
> > I've edited the machine's XML as instructed in
> > http://docs.openvswitch.org/en/latest/howto/libvirt/
> >
> > When I try to start the VM, i get
> > error: Cannot get interface MTU on 'ovsbr': No such device
>
> Is your OVS switch named "ovsbr"?
>
> >
> > Any ideas?
> >
> > (Note: I can't see the ovs switch in brctl show or any other regular
> > kernel tool, should it appear there?)
>
> On my Fedora 31 system at least, OVS devices are not visible in "brctl
> show", but they *are* visible with "ip link show". For example:
>
> 19: ovs-system: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN
> mode DEFAULT group default qlen 1000
>      link/ether 0a:f7:2a:85:08:7c brd ff:ff:ff:ff:ff:ff
> 20: ovsbr0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode
> DEFAULT group default qlen 1000
>      link/ether 96:92:7a:1d:a6:4c brd ff:ff:ff:ff:ff:ff
>
Hi, thanks a lot for the reply. It gave me the direction I needed. I
was using NetworkManager
to create the ovs bridge/port/interface, and it doesn't automatically
add the internal interface
that ovs-vsctl add-br does. Once i've setup my NetworkManager
connections properly, the
bridge appeared in ip link show and libvirt was able to find it.

Thanks a lot for the assistance!

 -Amir



>
> >
> > Versions:
> > openvswitch-2.10.1-3.fc30.x86_64
> > libvirt-daemon-5.1.0-9.fc30.x86_64
>
> The only differences on my system is the versions - I'm running Fedora
> 31, the openvswitch package is at 2.12, and libvirt is 6.0.0
> (unreleased), but this is the same setup I've had for at least a few
> years. The only other package on the system with "openvswitch" in the
> name is "network-scripts-openvswitch", and I doubt that would have any
> effect like what you're talking about.
>