Configuration Guide Configuring RMON
The HistoryControl group is used to set the sampling interval, sampling data source, and other control information.
The EthernetHistory group provides administrators with historical data, including statistics on network segment traffic,
error packets, broadcast packets, utilization, and number of collisions.
Alarm Group
The alarm group is used to monitor a specified Management Information Base (MIB) object. When the value of a MIB object
exceeds the preset upper limit or is lower than the preset lower limit, an alarm is triggered and the alarm is processed as an
event.
Event Group
The event group is used to define the event processing mode. When a monitored MIB object meets alarm conditions, an
event is triggered. An event can be processed in any of the following modes:
none: No action is taken.
log: Event-relevant information is recorded in the log record table so that administrators can view it at any time.
snmp-trap: A trap message is transmitted to the NMS to notify the NMS of the event occurrence.
log-and-trap: Event-relevant information is recorded in the log record table and a trap message is transmitted to the
NMS.
Working Principle
RMON supports multiple monitors and two data collection methods. Method 1: A dedicated RMON probe is used to collect
data and the NMS can directly acquire all information about the RMON MIB from the RMON probe. Method 2: RMON agents
are built into network devices (such as switches and routers) so that the devices have the RMON probe function. The NMS
uses basic commands of the Simple Network Management Protocol (SNMP) to exchange data with the RMON agents and
collect network management information. This method, however, is limited by device resources and information of only four
groups rather than all data of the RMON MIB is acquired.
The following figure shows an example of communication between the NMS and RMON agents. The NMS, through the
RMON agents running on devices, can acquire information about overall traffic, error statistics, and performance statistics of
the network segment where a managed network device interface is, thereby implementing remote management of network
devices.
Figure 4-2
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