ZyXEL Communications ES-2108 User Manual

ES-2108 Series User’s Guide

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Chapter 22 Access Control

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) and/or SNMP version 2c. The next figure illustrates an SNMP management 
operation. SNMP is only available if TCP/IP is configured.

Figure 69   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 such as number of 
packets received, node port status etc. 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 43   SNMP Commands

Get

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

Get Next 

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 Get Next operations.