Using log throttling to reduce duplicate Event Log and SNMP messages

A recurring event can generate a series of duplicate Event Log messages and SNMP traps in a relatively short time. As a result, the Event Log and any configured SNMP trap receivers may be flooded with excessive, exactly identical messages. To help reduce this problem, the switch uses log throttle periods to regulate (throttle) duplicate messages for recurring events, and maintains a counter to record how many times it detects duplicates of a particular event since the last system reboot.

When the first instance of a particular event or condition generates a message, the switch initiates a log throttle period that applies to all recurrences of that event. If the logged event recurs during the log throttle period, the switch increments the counter initiated by the first instance of the event, but does not generate a new message.

If the logged event repeats again after the log throttle period expires, the switch generates a duplicate of the first message, increments the counter, and starts a new log throttle period during which any additional instances of the event are counted, but not logged. Thus, for a particular recurring event, the switch displays only one message in the Event Log for each log throttle period in which the event reoccurs. Also, each logged instance of the event message includes counter data showing how many times the event has occurred since the last reboot. The switch manages messages to SNMP trap receivers in the same way.