RMON configuration
Remote Monitoring (RMON) is used for management devices to monitor and manage the managed devices on the network by implementing such functions as statistics collection and alarm generation. The statistics collection function enables a managed device to periodically or continuously track various traffic information on the network segments connecting to its ports, such as total number of received packets or total number of oversize packets received. 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 the RMON protocol and the Simple Network Management Protocol (SNMP) are used 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 an alarm threshold on the managed device and when that threshold is reached, the managed device sends a trap to the management device automatically. This method reduces the communication traffic between the management device and the managed device because the management device does not need to retrieve and compare the values of MIB variables multiple times. 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, management devices 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 by using basic SNMP operations to gather network management information, which, due to system resources limitation, only covers four groups of MIB information alarm, event, history, and statistics, in most cases.
The HP device adopts the second way and includes the RMON agent function. With the RMON agent function, the management device can obtain the traffic flow among the managed devices on each connected network segments and obtain information about error statistics and performance statistics for network management.
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