The trigger table (mteTriggerTable) lists any currently-defined trigger conditions. Triggers fall into three categories—existence, Boolean, and threshold.
An existence trigger tests for the existence of a MIB object instance; you can specify that the trigger occur by either the appearance, disappearance, or change in value of a MIB instance.
A Boolean trigger tests whether the value of a MIB object (base syntax integer) is equal, unequal, greater than, less than, less than or equal to, or greater than or equal to some defined value.
A threshold trigger verifies a MIB object (base syntax integer) in relation to either a rising threshold value, falling threshold value, or both.
You can configure both Boolean and threshold tests to trigger on an absolute value or a delta value over a determined polling interval.
Subordinate MIB tables exist within the trigger section of each type of trigger test. In other words, each type of trigger (existence, threshold, and Boolean) contains a table that stores added information about that type of trigger test.
For example, a trigger entry of a specific type of test in the mteTriggerTable creates a linked entry in the appropriate subtable. In turn, this subtable contains more specific information about the specific test.
A delta table also exists within the trigger tables. This table stores information about any delta values based on any Boolean and threshold triggers. The delta table stores a MIB object that indicates whether any discontinuities occurred for any delta trigger (for example, a router reset).
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Note: When determining discontinuity, the MIB object must be a time-based counter or number. When a polling interval expires and the event agent (router) needs to perform a delta calculation, it first checks the discontinuity MIB object for that trigger. If a discontinuity occurs, the agent does not perform the test for that trigger until the next polling interval. |
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