SNMP Intro

What is SNMP?

SNMP stands for Simple Network Management Protocol. It is used in network management systems to monitor network devices. It is part of Internet Protocol (IP) software suite.

Using SNMP, one can monitor and control a network device. Moreover, one can receive notification from a network device. A SNMP-managed system consists of three components: SNMP agents, Managed Devices, and Network Management Systems. A SNMP agent is a software process that manages network information on a Managed Device. A Managed Device is also called a SNMP-enabled device; routers, switches, PC, lab tops, or even smart phones are all examples of Managed Devices. A Network Management System is a computer that polls from Managed Devices and organizes the data in either textual or visual form.


Each Managed Device has one or more MIBs, which stand for Management Information Base. A management information base (MIB) is a type of database used to manage the devices in a communications network. It comprises a collection of objects to manage network devices such as routers and switches in a network.

Objects in the MIB are defined using a subset of Abstract Syntax Notation One (ASN.1) called “Structure of Management Information Version 2 (SMIv2)”. The software that performs the parsing is a MIB compiler.

The database is hierarchical (tree-structured) and entries are addressed through object identifiers. Three most notable MIBs are RFC1155-MIB, RFC1157-MIB, and RFC1213-MIB. These three MIBs are from three RFCs: RFC 1155, “Structure and Identification of Management Information for TCP/IP based internets”, and its two companions, RFC 1213, “Management Information Base for Network Management of TCP/IP-based internets”, and RFC 1157, “A Simple Network Management Protocol”.

This is an example of a SNMP-enabled network. The PC with pale green shadow is a Network Management System in this network (there could be more than one NMS). In this diagram, there are four Managed Devices or SNMP-enabled devices: switch, S0 router, S1 router, and the PC in 219.17.100.0 network.

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