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ware, and result in a response by the agent. The third opera-
tion type, the TRAP, allows the agent to send an unsolicited
message to the manager. This operation is typically used as an
alert to a potential problem, or a change in device status.
Using RMON
The switch offers an RMON subset contained within the basic
system management. The objects supported are some of the
most pertinent objects within RMON and include the Event,
Alarm, Statistics and History groups.
The Event group controls the generation and notification of
events from a device. An event can be the generation of an
SNMP trap and/or an entry into an event log. The Alarm group
takes periodic samples of variables, compares them to previous-
ly configured thresholds and generates an event if the threshold
has been exceeded. In order to implement the Alarm group,
the Event group must be activated.
The Statistics group provides counters for the traffic characteris-
tics of each object. The History group maintains a historical
representation of the Statistics counters for each object, based
on user-defined sample intervals.
RMON, Remote (network) MONitoring, was developed by the
Internet Engineering Task Force (IETF) and became a standard
in 1992 as RFC Number 1271 (now RFC 1757).
MIB Objects
A number of different MIB specifications have been defined for
managing network equipment; some are standard, others are
proprietary. SNMP-compliant devices typically support one or
more standard MIBs defined by the IETF, in the form of Request
for Comments (RFC) documents. These allow for a common
method of managing devices, such as bridges and hubs, and
network interfaces, such as Ethernet and Token Ring.
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MANAGING VIA SNMP AND RMON