Trigger test

An existence test monitors and manages the absence, presence, and change of a MIB object, for example, interface status. When a monitored object is specified, the system reads the value of the monitored object regularly.

• If the test type is Absent, the system triggers an alarm event and takes the specified action when the state of the monitored object changes to absent.

• If the test type is Present, the system triggers an alarm event and takes the specified action when the state of the monitored object changes to present.

• If the test type is Changed, the system triggers an alarm event and takes the specified action when the value of the monitored object changes.

A Boolean test compares the value of the monitored object with the reference value and takes action according to the comparison result. The comparison types include unequal, equal, less, lessorequal, greater, and greaterorequal. For example, if the comparison type is equal, an event is triggered when the value of the monitored object equals the reference value. The event will not be triggered again until the value becomes unequal and comes back to equal.

A threshold test regularly compares the value of the monitored object with the threshold values.

• A rising alarm event is triggered if the value of the monitored object is greater than or equal to the rising threshold.

• A falling alarm event is triggered if the value of the monitored object is smaller than or equal to the falling threshold.

• A rising alarm event is triggered if the difference between the current sampled value and the previous sampled value is greater than or equal to the delta rising threshold.

• A falling alarm event is triggered if the difference between the current sampled value and the previous sampled value is smaller than or equal to the delta falling threshold.

• A falling alarm event is triggered if the values of the monitored object, the rising threshold, and the falling threshold are the same.

• A falling alarm event is triggered if the delta rising threshold, the delta falling threshold, and the difference between the current sampled value and the previous sampled value is the same.

The alarm management module defines the set or notification action to take on alarm events.

If the value of the monitored object crosses a threshold multiple times in succession, the managed device triggers an alarm event only for the first crossing. For example, if the value of a sampled object crosses the rising threshold multiple times before it crosses the falling threshold, only the first crossing triggers a rising alarm event, as shown in Figure 53.