Public community string allows read privileges while private string allows write.

Protocol to gather information and configure network devices (printers, switches, servers etc. ). In this protocol there is a manager and a number of agents. The agents either wait for commands from the manager or send critical messages (trap) to the manager. V1/V2 use clear text protocols, while V3 uses encryption but can be brute forced.

Four types of SNMP commands: ◦ Read - used to monitor devices ◦ Write - used to configure devices ◦ Trap - used to ‘trap’ events from the device and report them back. ◦ Traversal operations - to determine variables a device supports.

General messages are sent on 161, and trap messages on 162

How SNMP works

Although it is difficult to get an overview of how SNMP works by just reading the standards, things are really simple.

On a typical SNMP usage scenario, one or more computers, called Network Managers or sometimes Element Managers, have the task of monitoring or managing a group of devices, called Network Elements.

Simple Architecture Diagram: SNMP Manager and SNMP Agent

The Network Element

The Network Element contains the SNMP Agent. We call Network Elementany type of device capable of communicating over the network.

Network Elements include, but are not limited to, routers, access servers, switches, bridges, hubs, IP telephones, IP video cameras, Microwave Links, DSLAMs, computer hosts, and printers.

To support SNMP, each Network Element must contain a software component called SNMP Agent, which runs all the time and communicates via SNMP with the Network Manager.

SNMP Agents contained in Network Elements, perform two main tasks:

• They expose data concerning the configuration, status and performance of the Network Element they reside, as variables.
• They send notifications concerning status change and faults of the Network Element they reside.

The SNMP Agent has local access and therefore knowledge of the Network Elements internal configuration, status and performance. This information is translated to SNMP specific form from the usually proprietary structure of the Network Element software.

The SNMP interface of the SNMP Agent allows unidirectional (read-only) or bidirectional (read-write) access to Network Element-specific information. This information is exchanged with the Network Manager.

The SNMP Agent uses an information database called Management Information Base (MIB) to store and retrieve information related with the status, performance and configuration of the Network Element it resides.