Every port on the integration bridge connected to an instance or other network resource is placed in a VLAN that is local to that virtual switch.

The Open vSwitch database on each host is independent of all other hosts, and the local VLAN database is not directly related to the physical network infrastructure. Instances in the same Neutron network on a particular host are placed in the same VLAN on the local integration bridge, but there is no VLAN ID consistency expected between hosts. That said, flow rules will be implemented on each host that maps the local VLAN ID to the ID associated with the respective Neutron network, allowing for traffic between hosts across the common VLAN. This behavior will be discussed in further detail later in this chapter.

Using the ovs-vsctl show command, you can identify the local VLAN tag of all ports on all virtual switches on the host. The following screenshot demonstrates this command in action on compute02:

Connected to the integration bridge are three interfaces named qvoce30da31-3a, qvoa943af89-8e, and qvo3de035cc-79. Two of the interfaces are in the same network and reside in the same local VLAN. The other interface, qvoa943af89-8e, is in a different network and thus is a different VLAN.