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Scenario - Open Virtual Network (OVN)

Overview

Operators can choose to utilize the Open Virtual Network (OVN) mechanism driver instead of Linux bridges or plain Open vSwitch for the Neutron ML2 plugin. This offers the possibility to deploy virtual networks and routers using OVN with Open vSwitch, which replaces the agent-based model used by the aforementioned architectures. This document outlines how to set it up in your environment.

The current implementation of OVN in OpenStack-Ansible should not be considered production-ready and makes the following architectural assumptions:

  • Each compute node will act as an OVN controller
  • Each compute node is eligible to serve as an OVN gateway node

NOTE: Physical VTEP integration is not yet supported.

Recommended reading

Since this is an extension of the basic Open vSwitch scenario, it is worth reading that scenario to get some background. It is also recommended to be familiar with OVN and networking-ovn projects and their configuration.

Prerequisites

  • Open vSwitch >= 2.9.0

* Networking-ovn at time of writing requires neutron-lib>=1.17.0. The overrides described here will ensure that version is installed.

* A successful deployment of OVN requires a dedicated network interface be attached to the OVS provider bridge. This is not handled automatially and may require changes to the network interface configuration file.

OpenStack-Ansible user variables

Set the following user variables in your /etc/openstack_deploy/user_variables.yml:

# Ensure the openvswitch kernel module is loaded
openstack_host_specific_kernel_modules:
  - name: "openvswitch"
    pattern: "CONFIG_OPENVSWITCH"
    group: "network_hosts"

neutron_plugin_type: ml2.ovn

neutron_plugin_base:
  - networking_ovn.l3.l3_ovn.OVNL3RouterPlugin

neutron_ml2_drivers_type: "vlan,local,geneve"

# 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 OVN w/ Open vSwitch, we override it to take into account
# the Open vSwitch bridge we are going to define outside of
# OpenStack-Ansible plays. All segmentation id ranges can be tweaked
# to suit the environment. VXLAN networks are not directly supported.

# When configuring Neutron to support only geneve tenant networks and
# vlan provider networks the configuration may resemble the following:
neutron_provider_networks:
  network_types: "geneve"
  network_geneve_ranges: "1:1000"
  network_vlan_ranges: "vlan"
  network_mappings: "vlan:br-provider"

# When configuring Neutron to support only vlan tenant networks and
# vlan provider networks the configuration may resemble the following:
neutron_provider_networks:
  network_types: "vlan"
  network_vlan_ranges: "vlan:102:199"
  network_mappings: "vlan:br-provider"

repo_build_upper_constraints_overrides: [neutron-lib>=1.17.0]

The overrides are instructing Ansible to deploy the OVN mechanism driver and associated OVN components. This is done by setting neutron_plugin_type to ml2.ovn.

The neutron_plugin_base override instructions Neutron to use OVN for routing functions rather than the standard L3 agent model.

The neutron_ml2_drivers_type override provides support for all type drivers supported by OVN.

Open Virtual Network (OVN) commands

The following commands can be used to provide useful information about...

The ovs-vsctl list open_vswitch command provides information about the open_vswitch table in the local Open vSwitch database:

root@aio1:~# ovs-vsctl list open_vswitch
_uuid               : 855c820b-c082-4d8f-9828-8cab01c6c9a0
bridges             : [37d3bd82-d436-474e-89b7-705aea634d7d, a393b2f6-5c3d-4ccd-a2f9-e9817391612a]
cur_cfg             : 14
datapath_types      : [netdev, system]
db_version          : "7.15.1"
external_ids        : {hostname="aio1", ovn-bridge-mappings="vlan:br-provider", ovn-encap-ip="172.29.240.100", ovn-encap-type="geneve,vxlan", ovn-remote="tcp:172.29.236.100:6642", rundir="/var/run/openvswitch", system-id="11af26c6-9ec1-4cf7-bf41-2af45bd59b03"}
iface_types         : [geneve, gre, internal, lisp, patch, stt, system, tap, vxlan]
manager_options     : []
next_cfg            : 14
other_config        : {}
ovs_version         : "2.9.0"
ssl                 : []
statistics          : {}
system_type         : ubuntu
system_version      : "16.04"

The ovn-sbctl show command provides information related to southbound connections. If used outside the ovn_northd container, specify the connection details:

root@aio1-neutron-ovn-northd-container-57a6f1a9:~# ovn-sbctl show
Chassis "11af26c6-9ec1-4cf7-bf41-2af45bd59b03"
    hostname: "aio1"
    Encap vxlan
        ip: "172.29.240.100"
        options: {csum="true"}
    Encap geneve
        ip: "172.29.240.100"
        options: {csum="true"}

root@aio1:~# ovn-sbctl --db=tcp:172.29.236.100:6642 show
Chassis "11af26c6-9ec1-4cf7-bf41-2af45bd59b03"
    hostname: "aio1"
    Encap vxlan
        ip: "172.29.240.100"
        options: {csum="true"}
    Encap geneve
        ip: "172.29.240.100"
        options: {csum="true"}

The ovn-nbctl show command provides information about networks known to OVN and demonstrates connectivity between the northbound database and neutron-server.

root@aio1-neutron-ovn-northd-container-57a6f1a9:~# ovn-nbctl show
switch 5e77f29e-5dd3-4875-984f-94bd30a12dc3 (neutron-87ec5a05-9abe-4c93-89bd-c6d40320db87) (aka testnet)
    port 65785045-69ec-49e7-82e3-b9989f718a9c
        type: localport
        addresses: ["fa:16:3e:68:a3:c8"]

The ovn-nbctl list Address_Set command provides information related to security groups. If used outside the ovn_northd container, specify the connection details:

root@aio1-neutron-ovn-northd-container-57a6f1a9:~# ovn-nbctl list Address_Set
_uuid               : 575b3015-f83f-4bd6-a698-3fe67e43bec6
addresses           : []
external_ids        : {"neutron:security_group_id"="199997c1-6f06-4765-89af-6fd064365c6a"}
name                : "as_ip4_199997c1_6f06_4765_89af_6fd064365c6a"

_uuid               : b6e211af-e52e-4c59-93ce-adf75ec14f46
addresses           : []
external_ids        : {"neutron:security_group_id"="199997c1-6f06-4765-89af-6fd064365c6a"}
name                : "as_ip6_199997c1_6f06_4765_89af_6fd064365c6a"

root@aio1:~# ovn-nbctl --db=tcp:172.29.236.100:6641 list Address_Set
_uuid               : 575b3015-f83f-4bd6-a698-3fe67e43bec6
addresses           : []
external_ids        : {"neutron:security_group_id"="199997c1-6f06-4765-89af-6fd064365c6a"}
name                : "as_ip4_199997c1_6f06_4765_89af_6fd064365c6a"

_uuid               : b6e211af-e52e-4c59-93ce-adf75ec14f46
addresses           : []
external_ids        : {"neutron:security_group_id"="199997c1-6f06-4765-89af-6fd064365c6a"}
name                : "as_ip6_199997c1_6f06_4765_89af_6fd064365c6a"

Additional commands can be found in upstream OVN documentation.

Notes

The ovn-controller service on compute nodes will check in as an agent and can be observed using the openstack network agent list command:

root@aio1-utility-container-35bebd2a:~# openstack network agent list
+--------------------------------------+------------------------------+------+-------------------+-------+-------+----------------+
| ID                                   | Agent Type                   | Host | Availability Zone | Alive | State | Binary         |
+--------------------------------------+------------------------------+------+-------------------+-------+-------+----------------+
| 4db288a6-8f8a-4153-b4b7-7eaf44f9e881 | OVN Controller Gateway agent | aio1 | n/a               | :-)   | UP    | ovn-controller |
+--------------------------------------+------------------------------+------+-------------------+-------+-------+----------------+

The HAproxy client and server timeout values have been increased from 50 seconds to 90 minutes for all load-balanced OVN-related services.

The HAproxy implementation in use may not properly handle active/backup failover for ovsdb-server with OVN. Work may be done to implement pacemaker/corosync or wait for active/active support.

Warranty

This implementation of OVN is not supported and should be considered only for development purposes. The architecture within OSA is subject to change. Reviews and suggestions are welcome.