3Com Switch 7750 Configuration Guide

748 CHAPTER 69: RMON CONFIGURATION
Commonly Used RMON
Groups
Event group
The event group is used to define the indexes of events and the processing
methods of the events. The events defined in an event group are mainly used in
alarm group and extended alarm group to trigger alarms.
You can specify a network device to act in one of the following ways in response
to an event:
■ Logging the event
■ Sending trap messages to the NMS
■ Logging the event and sending trap messages to the NMS
■ No processing
Alarm group
RMON alarm management enables monitors on specific alarm variables (such as
the statistics of a port). When the value of a monitored variable exceeds the
threshold, an alarm event is generated, which triggers the network device to act in
the set way. Events are defined in event groups.
With an alarm entry defined in an alarm group, a network device performs the
following operations accordingly:
■ Sampling the defined alarm variables (alarm-variable) once in each specified
period (sampling-time)
■ Comparing the sampled value with the set threshold and triggering the
corresponding events if the sampled value exceeds the threshold
Extended alarm group
With extended alarm entry, you can perform operations on the samples of an
alarm variable and then compare the operation result with the set threshold, thus
implement more flexible alarm functions.
With an extended alarm entry defined in an extended alarm group, the network
devices perform the following operations accordingly:
■ Sampling the alarm variables referenced in the defined extended alarm
expressions once in each specified period
■ Performing operations on sampled values according to the defined operation
formulas
■ Comparing the operation result with the set threshold and triggering
corresponding events if the operation result exceeds the threshold.
History group
After a history group is configured, the Ethernet switch collects network statistics
information periodically and stores the statistics information temporarily for later
retrieval. A history group can provide the history data of the statistics on network
segment traffic, error packets, broadcast packets, and bandwidth utilization.