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Configuring a Logical Interface to Be Tracked

VRRP can track whether a logical interface is up, down, or not present, and can change the priority of the switch based on the state of the interface, which might trigger a new master election. VRRP can also track the operational speed of a logical interface and update the priority of the switch when the speed crosses a configured threshold. For each VRRP group, you can track as many as 10 logical interfaces.

When interface tracking is enabled on a switch, you cannot assign the switch a priority of 255 to make it the master for the group.

• [edit interfaces interface-name unit logical-unit-number family inet address address vrrp-group group-id]

The interface specified is the interface to be tracked for the VRRP group. The priority-hold-time statement is the minimum length of time that must elapse between priority changes. If the priority changes because of a tracking event, the priority hold timer begins. If another tracking event or manual configuration change occurs while the timer is running, the new priority update is postponed until the timer expires. You might configure the priority-hold-time statement to prevent problems that could occur if there were multiple VRRP transitions in a short period of time.

The bandwidth-threshold statement specifies a threshold for the tracked interface. If the bandwidth of the tracked interface drops below the threshold value, the system subtracts the bandwidth threshold priority-cost value from the VRRP priority for the switch. You can create as many as five bandwidth-threshold statements for each tracked interface.

The interface priority-cost statement is the value to be subtracted from the VRRP priority when the tracked route goes down. The value can be 1 through 254. The sum of the costs for all tracked interfaces and routes must be less than or equal to the configured priority (so that subtracting all the costs results in a priority equal to or greater than 0).

Warning: On a QFabric system, do not apply interface tracking to a multichassis link aggregation group (MC-LAG) that includes an interface belonging to a network Node group device and an interface belonging to a server Node group device. If you do apply interface tracking to an MC-LAG configured in this way, a priority update will not occur if the state of the MC-LAG interface changes.

If you configure tracking for more than one interface, Junos OS subtracts the sum of the priority costs for the tracked interfaces from the VRRP priority if all the tracked interfaces fail. However, if you configure the interface priority-cost statement and the bandwidth threshold priority-cost statement, they are not added together. The switch uses only one priority cost for a tracked interface, as indicated in Table 1:

You must configure an interface priority cost only if you do not configure any bandwidth thresholds. If you do not configure an interface priority-cost value and the interface fails, Junos OS subtracts the bandwidth threshold priority-cost value of the lowest bandwidth threshold from the priority of the switch.