Connectivity Guide

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 Remote Access Controller, see RAC Traps, BMC Traps ,iDRAC7 and

iDRAC8 Traps.

Understanding Trap Severity

Traps often contain information about values recorded by probes or sensors. Probes and sensors monitor

critical components for values such as amperage, voltage, and temperature. When an event occurs on

your system, the Server Administrator sends information about one of the following event types to the

system management console:

• Information/Informational—An event that describes the successful operation of a unit, such as a

power supply turning on or a sensor reading returning to normal.

• Warning — An event that is not necessarily significant, but may indicate a possible future problem,

such as crossing a warning threshold.

• Critical/Error — A significant event that indicates actual or imminent loss of data or loss of function,

such as crossing a failure threshold or a hardware failure.