H3C Technologies H3C SR8800 - Manual (Page 119)

107
Configuring RMON
RMON overview
Introduction
Remote Monitoring (RMON) provides functions including statistics collection and alarm generation for
network management stations (NMSs) to monitor and manage devices. The statistics collection function
enables a managed device to periodically or continuously track traffic information, such as the count of
incoming packets and the count of incoming oversized packets, for the networks attached to its ports. The
alarm function enables a managed device to monitor the value of a specified MIB variable, log the event
and send a trap to the management device when the value reaches the threshold, such as the port rate
reaches a certain value or the potion of broadcast packets received in the total packets reaches a certain
value.
Both RMON and SNMP are for remote network management.
• RMON is implemented on the basis of the SNMP, and is an enhancement to SNMP. RMON sends
traps to the management device to notify the abnormality of the alarm variables by using the SNMP
trap packet sending mechanism. Although trap is also defined in SNMP, it is usually used to notify
the management device whether some functions on managed devices operate normally and the
change of physical status of interfaces. Traps in RMON and those in SNMP have different
monitored targets, triggering conditions, and report contents.
• RMON provides an efficient means of monitoring subnets and allows SNMP to monitor remote
network devices in a more proactive, effective way. The RMON protocol defines that when an
alarm threshold is reached on a managed device, the managed device sends a trap to the
management device automatically, so the management device does not need to get the values of
MIB variables for multiple times and compare them, thus greatly reducing the communication traffic
between the management device and the managed device. In this way, you can manage a large
scale of network easily and effectively.
Working mechanism
RMON allows multiple monitors (management devices). A monitor provides the following methods for
data gathering:
• Using RMON probes. Management devices can obtain management information from RMON
probes directly and control network resources. In this approach, RMON NMSs can obtain all
RMON MIB information.
• 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 commands 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 SR8800 routers adopt the second way and realize the RMON agent function. With the RMON
agent function, the management device can obtain the traffic that flows among the managed devices on