[OVN] Update the External Ports documentation
This patch is part of the solution for LP #2037294 and updates the documentation to explain the new "enable-chassis-as-extport-host" configuration as well as enhancing the documentation in general to better explain each configuration, database information and high availability for external ports. Change-Id: Iad048a71653dc791fc27585b509c02470e5d08a2 Related-Bug: #2037294 Signed-off-by: Lucas Alvares Gomes <lucasagomes@gmail.com>
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Lucas Alvares Gomes
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cd8816acd1
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@ -10,7 +10,7 @@ ML2/OVN leverages the use of OVN's `external ports
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feature.
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What is it
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~~~~~~~~~~
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----------
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The external ports feature in OVN allows for setting up a port that lives
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externally to the instance and is reponsible for replying to ARP requests
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@ -28,18 +28,107 @@ following VNICs:
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* macvtap
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* baremetal
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Also, ports of the type ``external`` will be scheduled on the gateway
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nodes (controller or networker nodes) in HA mode by the OVN Neutron
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driver. Check the `OVN Database information`_ section for more
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information.
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These ports can be listed in OVN with following command:
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OVN Database information
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~~~~~~~~~~~~~~~~~~~~~~~~
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.. code-block:: bash
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the ML2/OVN driver identifies a gateway node by the
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``ovn-cms-options=enable-chassis-as-gw`` and ``ovn-bridge-mappings``
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options in the external_ids column from the ``Chassis`` table in the
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OVN Southbound database:
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$ ovn-nbctl find Logical_Switch_Port type=external
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_uuid : 105e83ae-252d-401b-a1a7-8d28ec28a359
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ha_chassis_group : [43047e7b-4c78-4984-9788-6263fcc69885]
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type : external
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...
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.. end
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The next section will talk more about the different configurations for
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scheduling these ports and how they are represented in the OVN database.
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Scheduling and database information
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-----------------------------------
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Ports of the type ``external`` will be scheduled on nodes
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marked to host these type of ports via the `ovn-cms-options
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<http://www.ovn.org/support/dist-docs/ovn-controller.8.html>`_
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configuration. There are two supported configurations for these nodes:
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1. ``enable-chassis-as-extport-host``
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2. ``enable-chassis-as-gw``
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These options can be set by running the following command locally on each
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node that will act as a candidate to host these ports:
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.. code-block:: bash
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$ ovs-vsctl set Open_vSwitch . external-ids:ovn-cms-options=\"enable-chassis-as-extport-host\"
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$ ovs-vsctl set Open_vSwitch . external-ids:ovn-cms-options=\"enable-chassis-as-gw\"
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.. end
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The sections below will explain the differences between the two
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configuration values.
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Configuration: ``enable-chassis-as-extport-host``
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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When nodes in the cluster are marked with the
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``enable-chassis-as-extport-host`` configuration, the ML2/OVN driver
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will schedule the external ports onto these nodes. This configuration
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takes precedence over ``enable-chassis-as-gw``.
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With this configuration, the ML2/OVN driver will create one
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``HA_Chassis_Group`` per external port and it will be named as
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``neutron-extport-<Neutron Port UUID>``. For example:
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.. code-block:: bash
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$ ovn-sbctl list Chassis
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_uuid : fa24d475-9664-4a62-bb1c-52a6fa4966f7
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external_ids : {ovn-cms-options=enable-chassis-as-extport-host, ...}
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hostname : compute-0
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name : "6fd9cef6-4e9d-4bde-ab82-016c2461957b"
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...
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_uuid : a29ee8f6-5301-45f5-b280-a43e533d4d65
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external_ids : {ovn-cms-options=enable-chassis-as-extport-host, ...}
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hostname : compute-1
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name : "4fa76c10-c6ea-4ae9-b31c-bc69103fe6f9"
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...
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.. end
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.. code-block:: bash
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$ ovn-nbctl list HA_Chassis_Group neutron-extport-392a77f9-7c48-4ad0-bd06-8b55bba00bd1
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_uuid : 1249b761-24e3-414e-ae10-7e880e9d3cf8
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external_ids : {"neutron:availability_zone_hints"=""}
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ha_chassis : [0d6b9718-7718-45d2-a838-1deb40131442, ae6e64e7-f948-49b3-a171-c9cfb58c8b31]
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name : neutron-extport-392a77f9-7c48-4ad0-bd06-8b55bba00bd1
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.. end
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Also, for HA, there will be a limit of five Chassis per
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``HA_Chassis_Group``, meaning that even if there are more nodes marked
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with the ``enable-chassis-as-extport-host`` option, each group will
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contain up to five members. This limit has been imposed because OVN uses
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BFD to monitor the connectivity of each member in the group, and having
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an unlimited number of members can potentially put a lot of stress on OVN.
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In general, this option is used when there are specific requirements
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for ``external`` ports and they can not be scheduled on controllers or
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gateway nodes. The next configuration does the opposite and uses the
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nodes marked as gateway to schedule the ``external`` ports.
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Configuration: ``enable-chassis-as-gw``
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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For the majority of use cases where there are no special requirements
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for the ``external`` ports and they can be co-located with gateway ports,
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this configuration should be used.
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Gateway nodes are identified by the
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``enable-chassis-as-gw`` and `ovn-bridge-mappings
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<http://www.ovn.org/support/dist-docs/ovn-controller.8.html>`_
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configurations:
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.. code-block:: bash
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@ -52,67 +141,81 @@ OVN Southbound database:
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.. end
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For more information about both of these options, please
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take a look at the `ovn-controller documentation
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<http://www.ovn.org/support/dist-docs/ovn-controller.8.html>`_.
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These options can be set by running the following command locally on each
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gateway node (note, the ``ovn-bridge-mappings`` will need to be adapted
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to your environment):
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.. code-block:: bash
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$ ovs-vsctl set Open_vSwitch . external-ids:ovn-cms-options=\"enable-chassis-as-gw\" external-ids:ovn-bridge-mappings=\"public:br-ex\"
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.. end
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As mentioned in the `What is it`_ section, every time a Neutron port
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with a certain VNIC is created the OVN driver will create a port of the
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type ``external`` in the OVN Northbound database. These ports can be
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found by issuing the following command:
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type ``external`` in the OVN Northbound database.
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When the ``enable-chassis-as-gw`` configuration is used, the ML2/OVN
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driver will create one ``HA_Chassis_Group`` per network (instead
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of one per external port in the previous case) and it will be named as
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``neutron-<Neutron Network UUID>``.
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All ``external`` ports belonging to this network will share the same
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``HA_Chassis_Group`` and the group is also limited to a maximum of five
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members for HA.
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.. code-block:: bash
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$ ovn-nbctl find Logical_Switch_Port type=external
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_uuid : 105e83ae-252d-401b-a1a7-8d28ec28a359
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ha_chassis_group : [43047e7b-4c78-4984-9788-6263fcc69885]
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type : external
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...
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.. end
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The ``ha_chassis_group`` column indicates which HA Chassis Group that
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port belongs to, to find that group do:
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.. code-block:: bash
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# The UUID is the one from the ha_chassis_group column from
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# the Logical_Switch_Port table
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$ ovn-nbctl list HA_Chassis_Group 43047e7b-4c78-4984-9788-6263fcc69885
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$ ovn-nbctl list HA_Chassis_Group
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_uuid : 43047e7b-4c78-4984-9788-6263fcc69885
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external_ids : {}
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external_ids : {"neutron:availability_zone_hints"=""}
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ha_chassis : [3005bf84-fc95-4361-866d-bfa1c980adc8, 72c7671e-dd48-4100-9741-c47221672961]
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name : neutron-4b2944ca-c7a3-4cf6-a9c8-6aa541a20535
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.. end
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.. note::
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The external ports will be placed on a HA Chassis Group for the
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network that the port belongs to. Those HA Chassis Groups are named as
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``neutron-<Neutron Network UUID>``, as seeing in the output above. You
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can also use this "name" with the ``ovn-nbctl list`` command when
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searching for a specific HA Chassis Group.
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High availability
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-----------------
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The chassis that are members of the HA Chassis Group are listed in
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the ``ha_chassis`` column. Those are the gateway nodes (controller
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or networker nodes) in the deployment and it's where the ``external``
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ports will be scheduled. In order to find which gateway node the external
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ports are scheduled on use the following command:
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As hinted above, the ML2/OVN driver does provide high availability to the
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``external`` ports. This is done via the ``HA_Chassis_Group`` mechanism
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from OVN.
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On every ``external`` port there will be a column called
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``ha_chassis_group`` which points to the ``HA_Chassis_Group`` that the
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port belongs to:
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.. code-block:: bash
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$ ovn-nbctl find logical_switch_port type=external
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ha_chassis_group : 924fd0fe-3e84-4eaa-aa1d-41103ec511e5
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name : "287040d6-0936-4363-ae0a-2d5a239e55fa"
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type : external
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...
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.. end
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In the ``HA_Chassis_Group``, the members of each group are listed in the
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``ha_chassis`` column:
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.. code-block:: bash
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$ ovn-nbctl list HA_Chassis_Group 924fd0fe-3e84-4eaa-aa1d-41103ec511e5
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_uuid : 924fd0fe-3e84-4eaa-aa1d-41103ec511e5
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external_ids : {"neutron:availability_zone_hints"=""}
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ha_chassis : [3005bf84-fc95-4361-866d-bfa1c980adc8, 72c7671e-dd48-4100-9741-c47221672961]
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name : neutron-extport-287040d6-0936-4363-ae0a-2d5a239e55fa
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.. end
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.. note::
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There will be a maximum of five members for each group, this limit
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has been imposed because OVN uses BFD to monitor the connectivity of
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each member in the group, and having an unlimited number of members
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can potentially put a lot of stress on OVN.
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.. end
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When listing the members of a group there will be a column called
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``priority`` that contains a numerical value, the member with the highest
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``priority`` is the chassis where the ports will be scheduled on. OVN
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will monitor each member via BFD protocol, and if the chassis that is
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hosting the ports goes down, the ports will be automatically scheduled
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on the next chassis with the highest priority that is alive.
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.. code-block:: bash
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# The UUIDs are the UUID members of the HA Chassis Group
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# (ha_chassis column from the HA_Chassis_Group table)
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$ ovn-nbctl list HA_Chassis 3005bf84-fc95-4361-866d-bfa1c980adc8 72c7671e-dd48-4100-9741-c47221672961
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_uuid : 3005bf84-fc95-4361-866d-bfa1c980adc8
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chassis_name : "1a462946-ccfd-46a6-8abf-9dca9eb558fb"
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@ -126,11 +229,6 @@ ports are scheduled on use the following command:
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.. end
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Note the ``priority`` column from the previous command, the chassis with
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the highest ``priority`` from that list is the chassis that will have
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the external ports scheduled on it. In our example above, the chassis
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with the UUID ``1a462946-ccfd-46a6-8abf-9dca9eb558fb`` is the one.
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Whenever the chassis with the highest priority goes down, the ports will
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be automatically scheduled on the next chassis with the highest priority
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which is alive. So, the external ports are HA out of the box.
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In the example above, the Chassis with the UUID
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``1a462946-ccfd-46a6-8abf-9dca9eb558fb`` is the one that is hosting the
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external port ``287040d6-0936-4363-ae0a-2d5a239e55fa``.
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