SNMP based Network monitoring

This is an introductory post to the SNMP based network management series of posts. In this post I would want to elaborate on the Network monitoring tools, which use SNMP(Simple Network Management Protocol)  to poll and map network devices with statistics and graphs.

Before delving into tools such as net-snmp, mrtg, cacti and nagios, a brief insight into the concepts and terminologies of SNMP in this post would help us appreciate the tools better.

Simple Network Management Protocol (SNMP) is a UDP-based network protocol. It is used mostly in network management systems to monitor network-attached devices for conditions that warrant administrative attention. (wiki)

Simple Network Management Protocol is highly useful in monitoring the health, statistics and graphing resource utilization of network devices like switches, routers, data-multiplexers,  Ethernet-access devices, modems, servers and most of the other electronic devices which are part of the network.

In GNU/Linux machines, by default the ports 161 and 162 are used for SNMP.

An SNMP-managed network consists of three key components:

• Managed device, the device to be monitored/managed like a switch/router
• Agent — software which runs on managed devices, like snmpd on Linux machines
• Network management system (NMS) — software which runs on the manager, like nagios, cacti

To enhance the functionality of the snmp tools to incorporate additional features like configuration of specific devices, the concept of MIB is very helpful. MIB stands for Management Information Base, which increases the feature accessibility of devices being managed by SNMP.

SNMP protocol has had its growth with three versions until now.


SNMPv1: This is the first version of the protocol

SNMPv2c: This is the revised protocol, which includes enhancements of SNMPv1 in the areas of protocol packet types, transport mappings, MIB structure elements but using the existing SNMPv1 administration structure ("community based" and hence SNMPv2c).

SNMPv3: SNMPv3 defines the secure version of the SNMP. SNMPv3 also facilitates remote configuration of the SNMP entities.

In the posts to follow, we shall take a look at each of the important GNU/Linux utilities pertaining to SNMP