Zyxel GS2200-24 Руководство пользователя онлайн [270/332] 810932

Chapter 35 Access Control

GS2200-8/24 User’s Guide

270

35.7 Technical Reference

This section provides technical background information on the topics discussed in this chapter.

35.7.1 About SNMP

Simple Network Management Protocol (SNMP) is an application layer protocol used to manage and

monitor TCP/IP-based devices. SNMP is used to exchange management information between the

network management system (NMS) and a network element (NE). A manager station can manage

and monitor the Switch through the network via SNMP version one (SNMPv1), SNMP version 2c or

SNMP version 3. The next figure illustrates an SNMP management operation. SNMP is only available

if TCP/IP is configured.

Figure 178 SNMP Management Model

An SNMP managed network consists of two main components: agents and a manager.

An agent is a management software module that resides in a managed switch (the Switch). An

agent translates the local management information from the managed switch into a form

compatible with SNMP. The manager is the console through which network administrators perform

network management functions. It executes applications that control and monitor managed

devices.

The managed devices contain object variables/managed objects that define each piece of

information to be collected about a switch. Examples of variables include number of packets

received, node port status and so on. A Management Information Base (MIB) is a collection of

managed objects. SNMP allows a manager and agents to communicate for the purpose of accessing

these objects.

SNMP itself is a simple request/response protocol based on the manager/agent model. The

manager issues a request and the agent returns responses using the following protocol operations:

Table 111 SNMP Commands

COMMAND DESCRIPTION

Get Allows the manager to retrieve an object variable from the agent.

GetNext Allows the manager to retrieve the next object variable from a table or list within an agent.

In SNMPv1, when a manager wants to retrieve all elements of a table from an agent, it

initiates a Get operation, followed by a series of GetNext operations.