Adds Neutron OVS DVR Documentation

This patch adds documentation content to help users setup OVS-DVR.

Change-Id: I6bceb0741a3cbb0e14f726dfac634f0216ae9e89

doc/source/app-openvswitch-dvr.rst

@@ -0,0 +1,75 @@
+======================================
+Scenario - Using Open vSwitch with DVR
+======================================
+
+Overview
+~~~~~~~~
+
+Operators can choose to utilize Open vSwitch with Distributed Virtual
+Routing (DVR) instead of Linux Bridges or plain Open vSwitch for the
+neutron ML2 agent. This offers the possibility to deploy virtual routing
+instances outside the usual neutron networking node. This document
+outlines how to set it up in your environment.
+
+Recommended reading
+~~~~~~~~~~~~~~~~~~~
+
+We recommend that you read the following documents before proceeding:
+
+ * Neutron documentation on Open vSwitch DVR OpenStack deployments:
+   `<https://docs.openstack.org/neutron/latest/admin/deploy-ovs-ha-dvr.html>`_
+ * Blog post on how OpenStack-Ansible works with Open vSwitch:
+   `<http://trumant.github.io/openstack-ansible-dvr-with-openvswitch.html>`_
+
+Prerequisites
+~~~~~~~~~~~~~
+
+Configure your networking according the Open vSwitch setup:
+
+* Scenario - Using Open vSwitch
+  `<https://docs.openstack.org/openstack-ansible-os_neutron/latest/app-openvswitch.html>`_
+
+OpenStack-Ansible user variables
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Set the following user variables in your
+``/etc/openstack_deploy/user_variables.yml``:
+
+.. code-block:: yaml
+
+  # Ensure the openvswitch kernel module is loaded
+  openstack_host_specific_kernel_modules:
+    - name: "openvswitch"
+      pattern: "CONFIG_OPENVSWITCH"
+      group: "network_hosts"
+
+  ### neutron specific config
+  neutron_plugin_type: ml2.ovs.dvr
+
+  neutron_ml2_drivers_type: "flat,vlan"
+
+  # Typically this would be defined by the os-neutron-install
+  # playbook. The provider_networks library would parse the
+  # provider_networks list in openstack_user_config.yml and
+  # generate the values of network_types, network_vlan_ranges
+  # and network_mappings. network_mappings would have a
+  # different value for each host in the inventory based on
+  # whether or not the host was metal (typically a compute host)
+  # or a container (typically a neutron agent container)
+  #
+  # When using Open vSwitch, we override it to take into account
+  # the Open vSwitch bridge we are going to define outside of
+  # OpenStack-Ansible plays
+  neutron_provider_networks:
+    network_flat_networks: "*"
+    network_types: "vlan"
+    network_vlan_ranges: "physnet1:102:199"
+    network_mappings: "physnet1:br-provider"
+
+**Note:** The only difference to the Standard Open vSwitch configuration
+is the setting of the ``ml2_plugin_type``.
+
+Customization is needed to support additional network types such as vxlan,
+GRE or Geneve. Refer to the `neutron agent configuration
+<https://docs.openstack.org/neutron/latest/configuration/#configuration-reference>`_ for
+more information on these attributes.