HP 2910AL - Manual (Page 524)

Troubleshooting
Using the Event Log for Troubleshooting Switch Problems
To redisplay all hidden entries, including Event Log entries recorded prior to
the last reboot, enter the
show logging -a command.
Syntax: clear logging
Removes all entries from the event log display output.
CLI: Turning Event Numbering On
Syntax: [no] log-numbers
Turns event numbering on and off
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.
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