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

[Laine Stump]

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


> 
> 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.