H3C Technologies H3C S5120 Series Switches - Manual (Page 592)

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Working Mechanism
RMON allows multiple monitors (management devices). A monitor provides two ways of data gathering:
z Using RMON probes. Management devices can obtain management information from RMON
probes directly and control network resources. In this approach, management devices can obtain
all RMON MIB information.
z Embedding RMON agents in network devices such as routers, switches, and hubs to provide the
RMON probe function. Management devices exchange data with RMON agents using basic SNMP
operations to gather network management information, which, due to system resources limitation,
may not cover all MIB information but four groups of information, alarm, event, history, and
statistics, in most cases.
The H3C device adopts the second way and realizes the RMON agent function. With the RMON agent
function, the management device can monitor all the traffic flowing among the managed devices on all
connected LAN segments; obtain information about error statistics and performance statistics for network
management.
RMON Groups
Among the RMON groups defined by RMON specifications (RFC 2819), the realized public MIB of the
device supports the event group, alarm group, history group and statistics group. Besides, H3C 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:
z Log: Logging event related information (the occurred events, contents of the event, and so on) in
the event log table of the RMON MIB of the device, and thus the management device can check the
logs through the SNMP Get operation.
z Trap: Sending a trap to notify the occurrence of this event to the network management station
(NMS).
z Log-Trap: Logging event information in the event log table and sending a trap to the NMS.
z None: No action
Alarm group
The RMON alarm group monitors specified alarm variables, such as total number of received packets
(etherStatsPkts) on an interface. After you define an alarm entry the system gets the value of the
monitored alarm variable at the specified interval, when the value of the monitored variable is greater
than or equal to the upper threshold, an upper event is triggered; when the value of the monitored
variable is smaller than or equal to the lower threshold, a lower event is triggered. The event is then
handled as defined in the event group.