Neutron uses default settings to determine the type of routers that users are allowed to create. In addition, the settings also specify the number of routers that make up a VRRP group, the default HA network CIDR, and the default network type.

The following settings are specified within the Neutron configuration file at /etc/neutron/neutron.conf, and only need to be modified on the host(s) running the Neutron API service. In this environment, the neutron-server service runs on the controller01 node:

# Enable HA mode for virtual routers. (boolean value)
#l3_ha = false
#
# Maximum number of L3 agents which a HA router will be scheduled
# on. If it is to 0 then the router will be scheduled on every
# agent. (integer value)
#max_l3_agents_per_router = 3
#
# Subnet used for the l3 HA admin network. (string value)
#l3_ha_net_cidr = 169.254.192.0/18
#
# The network type to use when creating the HA network for an HA 
# router. By default or if empty, the first 'tenant_network_types'
# is used. This is helpful when the VRRP traffic should use a
# specific network which is not the default one. (string value)
#l3_ha_network_type =
# 

To set HA routers as the default router type for projects, set the l3_ha configuration option to True in neutron.conf. For this demonstration, the default value of False is sufficient.

To set a maximum number of L3 agents used for a virtual router, set  max_l3_agents_per_router accordingly. For this demonstration, the default value is sufficient and will mean that three network namespaces will be constructed to make up the VRRP virtual router.

To modify the network type used for HA routers, change the value of l3_ha_network_type. By default, the default project network type is used and is sufficient for this demonstration.

Once the changes have been made, restart the neutron-server service on the controller node for the changes to take effect.