I have been searching for days on a beginners guide or tutorial on understanding and using SNMP.

I am looking for a guide that starts from the very basics of explaining what an OID and MIB's are to how to use snmpget and snmpwalk effectively to actually start monitoring devices and services on servers.

This is stemming from how to use certain plugins in nagios. I have run across several guides that state you just need to "put in the OID of the device you want to monitor", but how do I find out what the OID is if I don't already know it? How do I read through the results of snmpwalk to find the correct OID?

So I ask you, does such a beginners guide exist that starts from the very basics? Thanks for your help in advance.

closed as off topic by Wesley, Scott Pack, Sven, Tom O'Connor, MDMarra Feb 20 '12 at 14:54

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Alright, let's see what I can go over on this post.

SNMP is based on the manager/agent model consisting of a manager, an agent, a database of management information, managed objects and the network protocol. The manager provides the interface between the human network manager and the management system. The agent provides the interface between the manager and the physical device(s) being managed.

The manager and agent use a Management Information Base (MIB) and a small set of commands to exchange information. The MIB is organized in a tree structure with individual variables, such as point status or description, being represented as leaves on the branches. A long numeric tag or object identifier (OID) is used to distinguish each variable uniquely in the MIB and in SNMP messages.

SNMP MESSAGES: SNMP uses five basic messages (Get, GetNext, GetResponse, Set and Trap) to communicate between the manager and the agent. The Get and GetNext messages allow the manager to request information for a specific variable. The agent, upon receiving a Get or GetNext message, will issue a GetResponse message to the manager with either the information requested or an error indication as to why the request cannot be processed.

A Set message allows the manager to request a change be made to the value of a specific variable in the case of an alarm remote that will operate a relay. The agent will then respond with a GetResponse message indicating the change has been made or an error indication as to why the change cannot be made.

The Trap message allows the agent to spontaneously inform the manager of an “important” event.

THE MIB: Each SNMP element manages specific objects with each object having specific characteristics. Each object/characteristic has a unique object identifier (OID) consisting of numbers separated by decimal points (e.g., These object identifiers naturally form a tree.

The MIB associates each OID with a readable label (e.g., dpsRTUAState) and various other parameters related to the object. The MIB then serves as a data dictionary or codebook that is used to assemble and interpret SNMP messages.

Beyond that, you need a good SNMP management software or device. A really good one will have trap information for your devices pre-configured, otherwise you may need to contact your hardware manufacturer's to find out more about how their device incorporates and utilizes SNMP.

  • +1. Also, a MIB Browser can help to make sense of the . It's almost as if MIBs are designed for machines and not people. They can be miserable to read without the proper tool. – Stefan Lasiewski Feb 17 '12 at 22:37
  • @StefanLasiewski Is there an MIB browser you would suggest? – Nic Young Feb 17 '12 at 23:48
  • It's been more then a year since I last looked, so I'll need to take a look. – Stefan Lasiewski Feb 18 '12 at 0:48

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