SNMPv1

The initial version of SNMP, SNMPvl is defined in RFC 1157, Simple Network Management Protocol (SNMP). The protocol's simplicity is apparent by the set of operations that are available. Figure 3-27 shows the basic SNMP messages, which the manager uses to transfer data from agents that reside on managed devices. These messages are described as follows:

■ Get Request: Used by the manager to request a specific MIB variable from the agent.

■ Get Next Request: Used after the initial get request to retrieve the next object instance from a table or list.

■ Set Request: Used to set a MIB variable on an agent.

■ Get Response: Used by an agent to respond to a manager's Get Request or Get Next Request message.

■ Trap: Used by an agent to transmit an unsolicited alarm to the manager. A Trap message is sent when specific conditions occur, such as a change in the state of a device, a device or component failure, or an agent initialization or restart.

Managed Device

Figure 3-27 SNMPv1 Message Types

Get Request

Manager

Retrieve Value of Specific MIB Variable

Get Next Request Retrieve Next Issuance of MIB Variable

Set Request Modify the Value of a MIB Variable

^_Get Response_

Contains Values of Requested Variable

Trap

Transmits an Unsolicited Alarm Condition

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