RMON (Remote Monitoring)


Remote Monitoring is an industry-standard method used to provide statistics on a network using Simple Network Management Protocol (SNMP) as the medium to report its findings. A switch configured for RMON enables a network administrator to obtain information about a switch's Layer 1 and Layer 2 environment.

RMON collects a lot of information regarding the switch's physical connections, performance, configuration, and other pertinent statistics. After RMON is configured on the switch, it runs continuously even when no clients are checking statistics. In fact, communication with an SNMP management station is not necessary. RMON can be configured to send Trap messages to notify a management station when an error condition occurs that exceeds a currently configured maximum threshold.

Nine different groups are available that can provide RMON information, four of which can be configured to provide information on a Cisco Catalyst switch without an external device, such as a Switched Port Analyzer (SPAN).

Cisco Catalyst switches support RMON information for Ethernet traffic for the following four groups:

  • Statistics ” This group 's basic function is to maintain utilization and error statistics. It monitors collisions, oversized packets, undersized packets, network jabber, packet fragmentation, and multicast and unicast bandwidth utilization.

  • History ” This group provides periodical statistical information, such as bandwidth utilization, frame counts, and error counts, that can be stored for later use.

  • Alarm ” This group enables you to configure thresholds for alarms and the intervals to check statistics. Any monitored event can be set to alarm the management station with a Trap message regarding an absolute or relative value or threshold.

  • Event ” This group's responsibility is to monitor log events on the switches. It also sends Trap messages to the management station with the time and date of the logged event. This enables the management station to be able to create customized reports based on the Alarm group's thresholds. Reports can be printed or logged for future use.

On Token Ring switches, RMON provides support for the following groups of the Token Ring extensions:

  • MAC-layer statistics ” A collection of statistics from the MAC sublayer of the Data Link layer, kept for each Token Ring interface. This group collects information such as the total number of MAC layer packets received and the number of times the port entered an error state.

  • Promiscuous statistics ” A collection of promiscuous statistics kept for non-MAC packets on each Token Ring interface. This group collects information such as the total number of good non-MAC frames received that were directed to a Logical-Link Control (LLC) broadcast address.

  • Ring station ” A collection of statistics and status information associated with each Token Ring station on the local ring. This group also provides status information for each ring being monitored.

  • Ring station order ” A listing order of stations on the monitored Token Ring network's rings.



CCNP CIT Exam Cram 2 (642-831)
CCNP CIT Exam Cram 2 (Exam Cram 642-831)
ISBN: 0789730219
EAN: 2147483647
Year: 2003
Pages: 213
Authors: Sean Odom

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