Managing Rmon - Cisco 500 series Administration Manual

Viewing Statistics

Managing RMON

Managing RMON
Cisco 500 Series Stackable Managed Switch Administration Guide
RMON (Remote Networking Monitoring) is an SNMP specification that enables an
SNMP agent in the switch to proactively monitor traffic statistics over a given
period and send traps to an SNMP manager. The local SNMP agent compares
actual, real-time counters against predefined thresholds and generates alarms,
without the need for polling by a central SNMP management platform. This is an
effective mechanism for proactive management, provided that you have the
correct thresholds set relative to your network's base line.
RMON decreases the traffic between the manager and the switch because the
SNMP manager does not have to poll the switch frequently for information, and
enables the manager to get timely status reports, because the switch reports
events as they occur.
With this feature, you can perform the following actions:
• View the current statistics (since the counter values were cleared). You can
also collect the values of these counters over a period of time, and then
view the table of collected data, where each collected set is a single line of
the History tab.
• Define interesting changes in counter values, such as "reached a certain
number of late collisions" (defines the alarm), and then specify what action
to perform when this event occurs (log, trap, or log and trap).
Viewing RMON Statistics
The Statistics page displays detailed information regarding packet sizes and
information regarding physical layer errors. The information displayed is according
to the RMON standard. An oversized packet is defined as an Ethernet frame with
the following criteria:
• Packet length is greater than MRU byte size.
• Collision event has not been detected.
• Late collision event has not been detected.
• Received (Rx) error event has not been detected.
• Packet has a valid CRC.
2
27