deploy-ovs-ha-dvr
supports augmentation using Virtual Router Redundancy Protocol (VRRP).
Using this configuration, virtual routers support both the
--distributed and --ha options.

Similar to legacy HA routers, DVR/SNAT HA routers provide a quick
fail over of the SNAT service to a backup DVR/SNAT router on an l3-agent
running on a different node.

SNAT high availability is implemented in a manner similar to the
deploy-lb-ha-vrrp and
deploy-ovs-ha-vrrp
examples where keepalived uses VRRP to provide quick
failover of SNAT services.

During normal operation, the primary router periodically transmits
heartbeat packets over a hidden project network that connects
all HA routers for a particular project.

If the DVR/SNAT backup router stops receiving these packets, it
assumes failure of the primary DVR/SNAT router and promotes itself to
primary router by configuring IP addresses on the interfaces in the
snat namespace. In environments with more than one backup
router, the rules of VRRP are followed to select a new primary
router.

Configuration example

The basic deployment model consists of one controller node, two or
more network nodes, and multiple computes nodes.

Controller node
configuration

1. Add the following to /etc/neutron/neutron.conf:

   [DEFAULT]
   core_plugin = ml2
   service_plugins = router
   router_distributed = True
   l3_ha = True
   l3_ha_net_cidr = 169.254.192.0/18
   max_l3_agents_per_router = 3

   When the router_distributed = True flag is configured,
   routers created by all users are distributed. Without it, only
   privileged users can create distributed routers by using
   --distributed True.

   Similarly, when the l3_ha = True flag is configured,
   routers created by all users default to HA.

   It follows that with these two flags set to True in the
   configuration file, routers created by all users will default to
   distributed HA routers (DVR HA).

   The same can explicitly be accomplished by a user with administrative
   credentials setting the flags in the openstack router create command:

   $ openstack router create name-of-router --distributed --ha

   Note

   The max_l3_agents_per_router determine the number of backup
   DVR/SNAT routers which will be instantiated.

2. Add the following to
   /etc/neutron/plugins/ml2/ml2_conf.ini:

   [ml2]
   type_drivers = flat,vxlan
   tenant_network_types = vxlan
   mechanism_drivers = openvswitch,l2population
   extension_drivers = port_security
   
   [ml2_type_flat]
   flat_networks = external
   
   [ml2_type_vxlan]
   vni_ranges = MIN_VXLAN_ID:MAX_VXLAN_ID

   Replace MIN_VXLAN_ID and MAX_VXLAN_ID with
   VXLAN ID minimum and maximum values suitable for your environment.

   Note

   The first value in the tenant_network_types option
   becomes the default project network type when a regular user creates a
   network.

Network nodes

1. Configure the Open vSwitch agent. Add the following to
   /etc/neutron/plugins/ml2/openvswitch_agent.ini:

   [ovs]
   local_ip = TUNNEL_INTERFACE_IP_ADDRESS
   bridge_mappings = external:br-ex
   
   [agent]
   enable_distributed_routing = True
   tunnel_types = vxlan
   l2_population = True

   Replace TUNNEL_INTERFACE_IP_ADDRESS with the IP address
   of the interface that handles VXLAN project networks.

2. Configure the L3 agent. Add the following to
   /etc/neutron/l3_agent.ini:

   [DEFAULT]
   ha_vrrp_auth_password = password
   interface_driver = openvswitch
   agent_mode = dvr_snat

Compute nodes

1. Configure the Open vSwitch agent. Add the following to
   /etc/neutron/plugins/ml2/openvswitch_agent.ini:

   [ovs]
   local_ip = TUNNEL_INTERFACE_IP_ADDRESS
   bridge_mappings = external:br-ex
   
   [agent]
   enable_distributed_routing = True
   tunnel_types = vxlan
   l2_population = True
   
   [securitygroup]
   firewall_driver = neutron.agent.linux.iptables_firewall.OVSHybridIptablesFirewallDriver

2. Configure the L3 agent. Add the following to
   /etc/neutron/l3_agent.ini:

   [DEFAULT]
   interface_driver = openvswitch
   agent_mode = dvr

   Replace TUNNEL_INTERFACE_IP_ADDRESS with the IP address
   of the interface that handles VXLAN project networks.

Keepalived VRRP health check

Known limitations

• There are certain scenarios where l2pop and distributed HA routers
  do not interact in an expected manner. These situations are the same
  that affect HA only routers and l2pop.