Configuring a Route to Be Tracked for a VRRP Group
VRRP can track whether a route is reachable (that is, the route exists in the routing table of the routing instance included in the configuration) and dynamically change the priority of the VRRP group based on the reachability of the tracked route, triggering a new master router election.
To configure a route to be tracked, include the following statements:
You can include these statements at the following hierarchy levels:
[edit interfaces interface-name unit logical-unit-number family inet address address vrrp-group group-id]
[edit interfaces interface-name unit logical-unit-number family inet6 address address vrrp-inet6-group group-id]
[edit logical-systems logical-system-name interfaces interface-name unit logical-unit-number family inet address address vrrp-group group-id]
[edit logical-systems logical-system-name interfaces interface-name unit logical-unit-number family inet6 address address vrrp-inet6-group group-id]
The route prefix specified is the route to be tracked for the VRRP group. The priority hold time is the minimum length of time that must elapse between dynamic priority changes. A route tracking event, such as adding a route to or removing a route from the routing table, might trigger one or more of the following:
The first tracking event initiates the priority hold timer, and also initializes the pending priority based on the current priority and the priority cost. However, the current priority remains unchanged.
A tracking event or a manual configuration change that occurs while the priority hold timer is on triggers a pending priority update. However, the current priority remains unchanged.
When the priority hold time expires, the current priority inherits the value from the pending priority, and the pending priority ceases.
This ensures that Junos OS does not initiate mastership elections every time a tracked route flaps.
If you have configured asymmetric-hold-time, VRRP does not wait for the priority hold time to expire before initiating mastership elections if a tracked route is removed from the routing table. For more information about asymmetric-hold-time, see Configuring the Asymmetric Hold Time for VRRP Routers.
The routing instance is the routing instance in which the route is to be tracked. If the route is in the default, or global, routing instance, specify the instance name as default.
Tracking a route that belongs to a routing instance from a different logical system is not supported.
The priority cost is the value to be subtracted from the configured VRRP priority when the tracked route goes down, forcing a new master router election. The value can be from 1 through 254.
The sum of the priority costs for all tracked routes must be less than or equal to the configured priority of the VRRP group. If you are tracking more than one route, the router applies the sum of the priority costs for the tracked routes (at most, only one priority cost for each tracked route) to the VRRP group priority.
Prior to Junos OS Release 15.1, an adjusted priority could not be zero. If the difference between the priority costs and the configured priority of the VRRP group was zero, the adjusted priority would become 1.
In Junos OS Release 15.1 and later, an adjusted priority can be zero.
The priority value zero (0) indicates that the current master router has stopped participating in VRRP. Such a priority value is used to trigger one of the backup routers to quickly transition to the master router without having to wait for the current master to time out.