Cisco Systems Dial NMS manual What is SNMPv2?, SNMPv1 Protocol Operations

Overview of Basic SNMP Building Blocks

What is SNMPv2?

•Application-wide data types—Including these seven types:

`Network addresses—Represent addresses from a protocol family. SNMPv1 supports only 32-bit IP addresses.

`Counters—Nonnegative integers that increase until they reach a maximum value; then, the integers return to zero. In SNMPv1, a 32-bit counter size is specified.

`Gauges—Nonnegative integers that can increase or decrease but retain the maximum value reached.

`Time ticks—A hundredth of a second since some event.

`Opaques—An arbitrary encoding that is used to pass arbitrary information strings that do not conform to the strict data typing used by the SMI.

`Integers—Signed integer-valued information. This data type redefines the integer data type, which has arbitrary precision in ASN.1 but bounded precision in the SMI.

`Unsigned integers—Unsigned integer-valued information that is useful when values are always nonnegative. This data type redefines the integer data type, which has arbitrary precision in ASN.1 but bounded precision in the SMI.

The SNMPv1 SMI defines structured tables that are used to group the instances of a tabular object (an object that contains multiple variables). Tables contain zero or more rows that are indexed to allow SNMP to retrieve or alter an entire row with a single Get, GetNext, or Set command.

SNMPv1 Protocol Operations

SNMP is a simple request-response protocol. The NMS issues a request, and managed devices return responses. This behavior is implemented by using one of four protocol operations:

•Get—Used by the NMS to retrieve the value of one or more object instances from an agent. If the agent responding to the Get operation cannot provide values for all the object instances in a list, the agent does not provide any values.

•GetNext—Used by the NMS to retrieve the value of the next object instance in a table or list within an agent.

•Set—Used by the NMS to set the values of object instances within an agent.

•Trap—Used by agents to asynchronously inform the NMS of a significant event.

What is SNMPv2?

SNMPv2 is an improved version of SNMPv1. Originally, SNMPv2 was published as a set of proposed Internet standards in 1993; currently, it is a Draft Standard. As with SNMPv1, SNMPv2 functions within the specifications of the SMI. SNMPv2 offers many improvements to SNMPv1, including additional protocol operations.

Basic Dial NMS Implementation Guide

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