How SNMP works?

SNMP has several components below the surface that enable performance information to be relayed back to the end-user. SNMP agents, SNMP managers, MIBs, and OIDs all work together to make these transfers possible.

The relationship between the SNMP manager and the SNMP agent is based on messages and commands. These messages come in a range of different forms. Some of the messages exchanged by the two components are listed below:

• GET – Sent when the SNMP manager is attempting to take information from the MIB to determine the value of a variable.

• RESPONSE – The agent sends a RESPONSE to the SNMP manager when replying to a GET request. This provides the SNMP manager with the variables that were requested originally.

• GETNEXT – The SNMP manager sends this message to the agent to get information from the next OID within the MIB tree.

• GETBULK – The SNMP agent uses the GETBULK message to pull data tables by using lots of different GETNEXT commands.

• SET – SET is a message sent by the SNMP manager to the agent to change configurations and issue commands.

• TRAP – An alert sent by the SNMP agent to notify the SNMP Manager when an event happens within the device.

A MIB or Management Information Base is a formatted text file that resides within the SNMP manager designed to collect information and organize it into a hierarchical format. The SNMP manager uses information from the MIB to translate and interpret messages before sending them onwards to the end-user.

Resources stored within a MIB are referred to as managed objects or management variables. The simplest way to think of a MIB is as the central hub of data inside the device. The MIB contains all of the performance data that is accessed when loading up a network monitoring tool.