8-18 RMON ConfigurationThis chapter includes these sections:z RMON Overviewz Configuring the RMON Statistics Collectionz Configuring the RMON Alarm Functionz Displaying and Maintaining RMONRMON OverviewIntroductionRemote Monitoring (RMON) is used to remotely monitor and manage devices on the network byimplementing such functions as statistics collection and alarm. The statistics collection functionenables a managed device to periodically or continuously track various traffic information onthe network segments that connect to its ports, such as total number of packets received ortotal number of oversize packets received. The alarm function enables a managed device tomonitor the value of a specified MIB variable, log the event and send a trap to the managementdevice when the value reaches the threshold, such as the port rate reaches a certain value orthe 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 forremote network management:z Implemented on the basis of SNMP, RMON is an enhancement to SNMP. RMON sendstraps to the management device to notify the abnormality of the alarm variables by usingthe SNMP trap sending mechanism. However, the trap function defined in SNMP is used tonotify the management device whether some functions on managed devices operatenormally and the change of physical status of interfaces. Traps in RMON and those inSNMP have different monitored targets, triggering conditions, and report contents.z RMON provides an efficient means of monitoring subnets and allows SNMP to monitorremote network devices in a more proactive and effective way. The RMON protocol definesthat when an alarm threshold is reached on a managed device, the managed deviceautomatically sends a trap to the management device, so the management device does notneed to get the values of MIB variables for multiple times and compare them, thus reducingthe traffic between the management device and the managed device. Large scale networkscan thus be managed easily and effectively.Working MechanismRMON allows multiple monitoring devices (management devices). A monitor collects data in thefollowing two ways:
