The Event services implements the Event MIB (RFC 2981). The Event MIB is divided into the following two sections, which define the Event services range of functions:
Trigger section
Event section
These sections are configured with tables in the snmpd.conf file according to the directives specified in section “DisMan Event MIB”.
Trigger section
The trigger section defines the MIB objects to be monitored and the conditions (trigger tests) with which an event is triggered, e.g.
mteTriggerValueID specifies the OID of the MIB object to be checked.
mteTriggerTest specifies the conditions to be tested, e.g.
existence: whether the MIC object specified in TriggerValueID exists.
boolean: whether the value of this MIB object matches a value defined in the BooleanTable (TriggerBooleanValue).
threshold: whether this value is above or below a threshold value defined in the ThresholdTable.
mteTriggerSampleType specifies whether the reference value is to be interpreted as an absolute value (absolute) or as a difference (delta) from a value determined during a previous query.
mteTriggerFrequency specifies the time interval (in seconds) between two contiguous queries.
Depending on the type of test, entries may require a further table:
mteTriggerExistenceTable: Object exists / disappears / changes value.
mteTriggerBooleanTable: Benchmark test of the object or delta value with the reference value.
mteTriggerThresholdTable: Object or delta value falls above / below threshold value.
If the test result is positive, a search is made in the EventTable for an appropriate entry for the action to be carried out.
Event section
The Event section defines which action - SNMP trap and/or SNMP SetRequest - is to be triggered in response to a successful trigger test, in the object EventAction:
notification (SNMP trap): The OID of the trap to be sent is defined in the EventNotificationTable.
set (SNMP SetRequest): The OID of the MIB object and the value to be set are defined in the EventSetTable.
Notifications
The Event MIB offers the following traps, which can be sent in response to triggered events.
mteTriggerFired reports that the trigger monitoring an object has been triggered.
mteTriggerRising reports that the threshold value has been exceeded.
mteTriggerFalling reports that the value has fallen below the threshold value.
Objects passed with a notification are entered in the Objects Table and specified in the corresponding entry in the:
Trigger Table
ExistenceTable / Boolean Table / Threshold Table and / or
Notification Table
The following notifications should be used only to help diagnose a problem, that has appeared in the error counters and cannot be found otherwise:
mteTriggerFailure reports that an attempt to check a trigger has failed.
mteEventSetFailure reports that an attempt to do a set in response to an event has failed.