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SNMP Polling

What is SNMP Polling?

SNMP Polling is a well defined and understood method of monitoring within the IT monitoring industry. SNMP stands for Simple Network Management Protocol, and is a standard way of monitoring hardware and software from nearly every vendor on the planet, such as Cisco, VMware, Juniper, Microsoft, Linux operating systems, and more.

There are two parts to SNMP, a Network Management Station (NMS) and a Management Agent (MA). The NMS, Opsview Monitor in this case, communicates with the management agent running on the hardware/software in question, using SNMP.

The management agent that runs on the hardware/software collects information about the aforementioned hardware/software and presents it in a logical fashion, allowing for it to be polled by the management station (Opsview Monitor).

This 'logical fashion' uses two key concepts: OIDs (Object Identifier) and MIBs (Management Information Base). SNMP works by querying objects, where an object is something containing data about a specific item within the hardware/software in question (e.g. temperature of a chip, etc.). SNMP identifies objects like this with an Object Identifier (OID).

OIDs are very structured and take a numbered, hierarchical tree structure. Most of the time, OIDs are translated into a more readable format, but you still might encounter situations where you will need to use the raw numbers. To find out more, see the guide here.

Tied closely to OIDs are the MIBs. A MIB is like a translator that helps your network management station (NMS) to understand the 'numbers' within the OID. This means that instead of seeing '1.3.6.1.4.1.311: 44.03', the MIB will translate and allows Opsview Monitor to display 'CPU0 Temperature: 44.03'. In essence, the MIB makes SNMP objects usable.

MIBs can be downloaded from the hardware/software vendor and loaded into Opsview Monitor by installing them into your distribution's designated MIB directories.

SNMP Security

There are three versions of the SNMP protocol supported in Opsview Monitor:

  • SNMP v1
  • SNMP v2c
  • SNMP v3

SNMP v1 and SNMP v2c are very similar in their configuration. An administrator configures a field known as the community string, which is the authentication string (i.e. password) that the NMS needs to get the data from the MA. This is how Opsview Monitor can log in to the router to get the information about it.

SNMP v3 is more secure in that it allows an administrator to set a username, an authentication algorithm, an authentication password, a privacy algorithm, AND a privacy password. All of these must be entered correctly within Opsview Monitor in order to allow access to the router/devices information.

In the screen below, both SNMP v1/v2c and v3 are configured:

Example SNMP configuration on a Draytek router
 
These credentials must be entered into Opsview Monitor in order to allow the monitoring of the Host in question.
 
More information about Opsview's network monitoring capabilities can be found here.

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