Reference Guide

28 Introduction
Initiating Management Actions
Management actions can be performed using the SNMP Set command. These actions can consist of
configuring a phone number for the system’s owner, rebooting a system, or changing the asset tag of the
system. See the previous section, "SNMP Security," for limitations on Set operations.
SNMP Traps
SNMP is frequently used to monitor systems for fault conditions such as temperature violations,
hard drive failures, and so on. Management applications can monitor for these conditions by polling the
appropriate OIDs with the Get command and analyzing the returned data. This method has its
drawbacks. If it is done frequently, significant amounts of network bandwidth can be consumed. If it is
done infrequently, the response to the fault condition may not occur in a timely fashion. SNMP traps
avoid these limitations of the polling method.
An SNMP trap is an asynchronous event indicating that something significant has occurred. This is
analogous to a pager receiving an important message, except that he SNMP trap frequently contains all
the information needed to diagnose a fault.
Two drawbacks to SNMP traps are that they are sent using UDP, which is not a guaranteed delivery
mechanism, and that they are not acknowledged by the receiver.
An SNMP trap message contains the trap’s enterprise OID, the agent IP address, a generic trap ID, the
specific trap ID, a time stamp, and zero or more variable bindings (varbinds). The combination of an
enterprise OID and a specific trap ID uniquely identifies each Server Administrator-defined trap.
A varbind consists of an OID and its value and provides additional information about the trap.
In order for a management system to receive SNMP traps from a managed system, the node must be
configured to send traps to the management system. Trap destination configuration is dependent on the
operating system. When this configuration is done, a management application on the management
system can wait for traps and act on them when received.
For a list of traps supported by the server administrator SNMP subagent, see "Traps."