Designing and Managing Behavior Models - Using Trap Masks - About Trap Masks -
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About Trap Masks

The figure below depicts the role that a trap mask plays in a behavior model.

Note that a trap mask is like a poll in that it is tied to one or more alarms by the triggers it can fire. If there are no pending alarm transitions that the mask can affect, the mask is disabled in the sense that it will not be applied to any incoming SNMP traps.

Assuming that the mask can affect an alarm transition, the mask is applied to SNMP traps as they arrive and determines whether it should fire a trigger in response to the trap. A mask can fire a trigger in one of two ways:

• A trap mask can fire a simple trigger. A mask designed to fire this type of trigger looks only at the Enterprise, Generic trap, and Specific trap fields in a trap's Protocol Data Unit (PDU). If these fields meet predefined conditions, the mask fires a trigger. All the triggers that this mask ever fires will have the same name.
• A mask can also fire a trigger from a trigger function by calling the FireTrigger() function. This type of mask looks at the fields mentioned above to determine whether it should call its trigger function. If called, this trigger function generally looks at the trap's variable bindings and may fire one of several triggers depending on the contents of the variable bindings.

If a mask fires a trigger, that trigger interacts with the alarm system just as a trigger fired by a poll does. If the necessary attributes of the trigger match the corresponding attributes of a pending alarm transition, a state transition occurs.