With the Object tracking feature, you can track the state (up/down) of various objects in the system using keepalive probes, and notify registered applications when the state changes. In particular, object tracking is used to monitor Interface states and routes states, where routes can be static routes, the DHCP client default route, or PBR next hops.
The purpose of object tracking is to track the state (up/down) of various objects in the system using keepalive probes, and notify registered applications when the state changes. Configuring object tracking is a two-stage operation:
The first stage is to define Respond Time Reports (RTRs), the basic building blocks of object tracking. RTRs actively monitor the reachability state of remote devices by generating probes at regular intervals. Each RTR, identified by a unique number, monitors one remote device, and learns the state of the device: up or down. The state of the RTR reflects the state of the device it is monitoring – either up or down.
The second stage consists of defining Object Trackers using RTRs. The definition of object trackers is recursive. A simple object tracker monitors a single RTR, and its state directly reflects the state of the RTR. A more advanced object tracker is a track list, which is composed of multiple simple object trackers. The state of the track list is calculated based on the states of the objects in the list. Because a track list is itself an object tracker, the objects in a track list can be previously-defined track lists.
You can view a track list as monitoring the health of an entire group of remote devices. You can define how to calculate the overall health of the group based on the health (up/down) state of each individual device. For example, you can specify that the overall state is up only if all remote devices are up, or if at least one device is up. Alternatively, you can base the overall state on a threshold calculation.
Using object tracking, different applications can register with the tracking process, track the same remote devices, and each take different action when the state of the remote devices changes.
