Hi, I was playing with OpenStack Neutron with OVS plugin. When I launch VMs, I noticed that there is a Linux bridge (qbrxxx) created for each VM, which is then connected to the OVS bridge (ovs-int). See the following.

            VM0           VM2
             |             |
          qbrXXX        qbrYYY  (per-VM linux bridges)
             |             |
             |             |                   
            br-int (OVS bridge)
                    |
                 br-eth

My question is, why couldn't VMs be directly connected to br-int (without qbr Linux bridges)? Why do we create additional Linux bridges between OVS bridge and VMs? What is the role of Linux bridges here?

Thanks!