SNMP Reference Guide

system and network management data is not confidential, this limited security is acceptable for Get types

of requests. On the other hand, this security is not acceptable for Set types of operations where an SNMP

request could power off a system, reconfigure a redundant array of independent disks (RAID) card, and so

on. Dell has chosen not to support SNMP Set operations for this reason.

NOTE: The default SNMP agent configuration usually includes a SNMP community name such as

public. For security reasons, change the SNMP community names from their default values. For

information about changing SNMP community names, see the Dell OpenManage Server

Administrator User’s Guide available on the Dell Support website at dell.com/openmanagemanuals.

NOTE: As of iDRAC7 firmware release r1.30.30, iDRAC7 supports SNMP query operations (GET,

GETNEXT, GETBULK) via the SNMPv3 protocol, in addition to supporting query operations via the

SNMP v1 and SNMP v2c protocols. More specifically, iDRAC7 now supports the SNMP User Security

Model (USM).

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 the 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 Instrumentation Service, see Instrumentation

Traps. For information on Server Administrator Storage Management traps, see Storage Management

Alert Reference.

For a list of traps supported by the Remote Access Controller, see RAC Traps, BMC Traps and iDRAC7

Traps.