Bridge interface configuration


This appendix explores physical interface configuration options available for OVS and OVN charms.

Available configuration options

For both OVS and OVN charms there is a need to provide physical interfaces for vSwitch bridges in order to be able to use VLAN and flat provider networks in Neutron:

  • OVS charms with data-port config: * neutron-openvswitch; * neutron-gateway;

  • OVN charms with bridge-interface-mappings config: * ovn-chassis; * ovn-dedicated-chassis.


Any changes (subsequent to the initial setting) made to the value of option data-port will merely add the new values along with the existing ones. If removal of old values is desired, they have to be done manually through the command ovs-vsctl in the affected units. If the new values conflict with the previous ones, it may cause a network outage as seen in bug LP #1915967.

Utilising one interface for multiple purposes

It is common to use a single network interface for providing network access to different types of workloads. Workloads such as OpenStack API services and Ceph may use VLAN interfaces at the host level or via VLAN-specific container bridges. Neutron services may rely on OVS bridges with physical network interfaces or bonds used as virtual switch uplinks. The following diagram shows how this can be achieved

+----------------+      +-----------------+
|      LXD       |      |VM or router port|
| container port |      +-----------------+
+----------------+              ||
        ||              +-----------------+
        ||              |   br-int (OVS)  |
+----------------+      +-----------------+
|  br-bond1.100  |              ||
|  Linux bridge  |      +-----------------+
| with L3 config |      |br-provider (OVS)|
+----------------+      +-----------------+
        ||                      ||
+----------------+      +-----------------+
|    bond1.100   |      |      bond1      |
|  no L3 config  |      |  no L3 config   |
+----------------+      +-----------------+
                           ||         ||
                        +------+   +------+
                        | hwe0 |   | hwe1 |
                        +------+   +------+

bond1 configured at the Linux kernel level can have VLAN interfaces such as bond1.100 which will make all traffic tagged with VLAN 100 to be forwarded to bond1.100 instead of bond1 so it will not reach br-provider. In this example, all untagged and tagged traffic, except for VLAN 100, will be forwarded to br-provider via bond1.

Any VLAN interface explicitly configured on top of bond1 will make its VLAN unusable in Neutron through the associated provider bridge because the inbound traffic for that VLAN will always be intercepted by a bond1.<vid> interface at the kernel level.


bond1 must not have any L3 configuration for this setup to work.

This allows VLAN provider networks to be used for a range of VLANs dedicated for use with Neutron in conjunction with some VLANs dedicated to host workloads.

Charm configuration examples

The following configuration assumes the setup mentioned above and that there are no VLAN tenant networks - only VLAN provider networks (thus the vlan-ranges option only includes a physnet name).

For OVS deployments the charm configuration would look like this:

juju config neutron-api vlan-ranges='dcfabric'
juju config neutron-openvswitch data-port='br-provider:bond1' bridge-mappings='dcfabric:br-provider' vlan-ranges='dcfabric'
juju config neutron-gateway data-port='br-provider:bond1' bridge-mappings='dcfabric:br-provider' vlan-ranges='dcfabric'

Whereas for OVN deployments:

juju config neutron-api vlan-ranges='dcfabric'
juju config ovn-chassis bridge-interface-mappings='br-provider:bond1' ovn-bridge-mappings='dcfabric:br-provider'
juju config ovn-dedicated-chassis bridge-interface-mappings='br-provider:bond1' ovn-bridge-mappings='dcfabric:br-provider'

To configure a VLAN provider network the following command can be used with any segment ID other than 100 as bond1.100 is present:

# --external is only needed for setups targeted at using floating IPs.
openstack network create --external --provider-network-type vlan --provider-physical-network dcfabric --provider-segment 99