A VRRP virtual router has a virtual IP address that can serve as the default gateway for hosts in the network. The master router owns the IP address until a failover event occurs, at which time a backup router becomes the new master and takes over the IP and associated routing duties.

Due to limitations with keepalived, Neutron HA routers do not completely follow the VRRP networking conventions described up to this point. Neutron assigns a single virtual IP to an HA router, and that virtual IP is only configured on the master router in the group at any given time. While the address does fail over between routers during a failover event, it is not actually used as a gateway address for any network. As HA routers are created, a new virtual IP address is assigned to the respective group.

Instead of using virtual addresses for each connected subnet, Neutron uses the virtual_ipaddress_excluded configuration section found within the keepalived configuration file to specify routes, addresses, and their respective interfaces that should be configured when a router becomes master for the group. Likewise, the interface configuration will be removed once the router becomes a backup router. The following screenshot demonstrates various interfaces and routes that will be modified:

The keepalived configuration file for an HA router will be discussed in further detail later in this chapter.