Open Virtual Switch

Install package

# apt-get install openvswitch-switch

Use em2 for VM network

# nano -w /etc/network/interfaces

+ auto em2
+ iface em2 inet manual
+         up ifconfig $IFACE 0.0.0.0 up
+         down ifconfig $IFACE down

Reboot or to enable em2 without rebooting

# ifconfig em2 up

Configure virtual bridge

# ovs-vsctl add-br br0
# ovs-vsctl add-port br0 em2

Disable default KVM network

# virsh net-destroy default
# virsh net-deactivate default
# virsh net-undefine default

Define OVS networks for KVM

I.e. em2 network has untagged and tagged VLANs and we need one network for untagged VLAN and one network for tag 33 VLAN

# nano -w ovs-network-V0.xml

<network>
  <name>ovs-network-V0</name>
  <forward mode='bridge'/>
  <bridge name='br0'/>
  <virtualport type='openvswitch'/>
</network>

# nano -w ovs-network-V33.xml

<network>
  <name>ovs-network-V33</name>
  <forward mode='bridge'/>
  <bridge name='br0'/>
  <virtualport type='openvswitch'/>
  <vlan>
      <tag id='33'/>
  </vlan>
</network>

Enable networks for KVM VMs

# virsh net-define ovs-network-V0.xml
# virsh net-start ovs-network-V0
# virsh net-autostart ovs-network-V0

# virsh net-define ovs-network-V33.xml
# virsh net-start ovs-network-V33
# virsh net-autostart ovs-network-V33

# virsh net-list

 Name                 State      Autostart     Persistent
----------------------------------------------------------
 ovs-network-V0       active     yes           yes
 ovs-network-V33      active     yes           yes

You can use these networks in VM configuration from “Virtual Machine Manager” GUI.