3Com Switch 4800G 24-Port Configuration Manual page 942

942 C 76: RMON C
HAPTER
RMON Groups
n
ONFIGURATION
information but four groups of information, alarm, event, history, and statistics,
in most cases.
The device adopts the second way. By using RMON agents on network monitors,
an NMS can obtain information about traffic size, error statistics, and performance
statistics for network management.
Among the ten RMON groups defined by RMON specifications (RFC 1757), 3Com
series Ethernet switches support the event group, alarm group, history group and
statistics group. Besides, 3Com also defines and implements the private alarm
group, which enhances the functions of the alarm group. This section describes
the five kinds of groups in general.
Event group
The event group defines event indexes and controls the generation and
notifications of the events triggered by the alarms defined in the alarm group and
the private alarm group. The events can be handled in one of the following ways:
Logging events in the event log table
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Sending traps to NMSs
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Both logging and sending traps
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No action
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Alarm group
The RMON alarm group monitors specified alarm variables, such as statistics on a
port. If the sampled value of the monitored variable is bigger than or equal to the
upper threshold, an upper event is triggered; if the sampled value of the
monitored variable is lower than or equal to the lower threshold, a lower event is
triggered The event is then handled as defined in the event group.
The following is how the system handles entries in the RMON alarm table:
1 Samples the alarm variables at the specified interval.
2 Compares the sampled values with the predefined threshold and triggers events if
all triggering conditions are met.
If a sampled alarm variable overpasses the same threshold multiple times, only the
first one can cause an alarm event. That is, the rising alarm and falling alarm are
alternate.
Private alarm group
The private alarm group calculates the sampled values of alarm variables and
compares the result with the defined threshold, thereby realizing a more
comprehensive alarming function.
System handles the prialarm alarm table entry (as defined by the user) in the
following ways:
Periodically samples the prialarm alarm variables defined in the prialarm
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formula.
Calculates the sampled values based on the prialarm formula.
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