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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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17.1.6 SNMP traps<br />

In this illustration, we see the following progression:<br />

1. The user executes a walk on ifType, which the manager implements by first<br />

executing a getNext on ifType. This is forwarded to the <strong>TCP</strong>/<strong>IP</strong> subagent by<br />

the SNMP agent.<br />

2. The subagent obtains the next valid value following ifType, ifType.1, <strong>and</strong><br />

returns this value to the agent. The agent passes this information back to the<br />

manager.<br />

3. The manager takes the ifType.1 response <strong>and</strong> executes a getNext for it.<br />

4. The subagent locates ifType.1 <strong>and</strong> returns the next valid value: ifType.2.<br />

5. The manager executes a getNext for ifType.2<br />

6. The subagent returns ifType.3<br />

7. The manager executes a getNext for ifType.3<br />

8. The subagent returns ifMtu.1<br />

9. The manager recognizes that ifMtu.1 is outside the scope of ifType, <strong>and</strong><br />

assumes that the walk is complete.<br />

Traps are asynchronous notifications of events occurring within an SNMP<br />

community. They can be generated both by SNMP agents <strong>and</strong> SNMP<br />

subagents. Additionally, they can be RFC architected (called a generic trap type)<br />

or they can be proprietary (called enterprise-specific). Architected traps, defined<br />

in RFC 1215, are as follows:<br />

coldStartEvent Notifies managers that the SNMP agent is reinitializing<br />

<strong>and</strong> that the configuration might have been altered. This<br />

trap belongs to the RFC 1213-architected System group,<br />

<strong>and</strong> is therefore supported by the SNMP agent.<br />

warmStartEvent Notifies managers that the SNMP agent is reinitializing,<br />

but there has been no alteration of the configuration. This<br />

trap belongs to the RFC 1213-architected System group,<br />

<strong>and</strong> is therefore supported by the SNMP agent.<br />

linkDownEvent Notifies managers that an interface has been deactivated.<br />

Information identifying the interface is included in the trap.<br />

This trap belongs to the RFC 1213-architected Interface<br />

group <strong>and</strong> is usually supported by a <strong>TCP</strong>/<strong>IP</strong> specific<br />

subagent.<br />

638 <strong>TCP</strong>/<strong>IP</strong> <strong>Tutorial</strong> <strong>and</strong> <strong>Technical</strong> <strong>Overview</strong>

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