Collaboration fundamentals

The Track module collaborates with detection modules and application modules.

The detection module sends the detection result of the tracked object to the Track module. The Track module changes the status of the track entry as follows:

• If the tracked object operates correctly, the state of the track entry is positive. For example, the track entry state is Positive in one of the following conditions:

  • The target interface is up.

  • The target network is reachable.

• If the tracked object does not operate correctly, the state of the track entry is Negative. For example, the track entry state is Negative in one of the following conditions:

  • The target interface is down.

  • The target network is unreachable.

• If the detection result is invalid, the state of the track entry is NotReady. For example, the track entry state is NotReady if its associated NQA operation does not exist.

The following detection modules can be associated with the Track module:

• NQA.

• BFD.

• Interface management.

• Route management.

You can associate a track entry with an object of a detection module, such as the state of an interface or reachability of an IP route. The state of the track entry is determined by the state of the tracked object.

You can also associate a track entry with a list of objects called a tracked list. The state of a tracked list is determined by the states of all objects in the list. The following types of tracked lists are supported:

• Boolean AND list—The state of a Boolean AND list is determined by the states of the tracked objects using the Boolean AND operation.

• Boolean OR list—The state of a Boolean OR list is determined by the states of the tracked objects using the Boolean OR operation.

• Percentage threshold list—The state of a percentage threshold list is determined by comparing the percentage of positive and negative objects in the list with the percentage thresholds configured for the list.

• Weight threshold list—The state of a weight threshold list is determined by comparing the weight of positive and negative objects in the list with the weight thresholds configured for the list.

The following application modules can be associated with the Track module:

• VRRP.

• Static routing.

• PBR.

• Interface backup.

• Redundancy group.

• EVI IS-IS.

• VPLS.

• MPLS L2VPN.

• EAA.

When configuring a track entry for an application module, you can set a notification delay to avoid immediate notification of status changes.

When the delay is not configured and the route convergence is slower than the link state change notification, communication failures occur. For example, when the master in a VRRP group detects an uplink interface failure through Track, Track immediately notifies the master to decrease its priority. A backup with a higher priority then preempts as the new master. When the failed uplink interface recovers, the Track module immediately notifies the original master to restore its priority. If the uplink route has not recovered, forwarding failure will occur.