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Can't find a sensor for my device in PRTG but I believe it supports SNMP. How to proceed?



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I have a device that supposedly supports SNMP, I've been through the Available Sensor Types but couldn't find a sensor that matches my device name/model.

Is there a way to monitor the device? Do I need to use custom sensors? Do you have any further recommendations on how to monitor it?

mib oidlib prtg snmp snmplibrary

Created on Aug 5, 2015 1:52:10 PM by  Luciano Lingnau [Paessler Support]

Last change on Aug 12, 2015 4:47:46 AM by  Felix Saure [Paessler Support]

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This article applies to PRTG Network Monitor 19 or later

Custom Monitoring of Devices via SNMP

IMPORTANT: The steps described in this article only apply to PRTG on Premises, not to PRTG hosted by Paessler.

This is a guide to Monitor your device if it supports SNMP. It provides the instructions for adding a new SNMP Library sensor to PRTG by importing an SNMP MIB file.

As an example, we use the MIB of Synology, but the approach applies to almost all MIB files and systems. Note: PRTG already comes with built-in sensors for logical disks, physical disks, and a system health sensor for Synology NAS systems.

Step 1: Ensure That Your Device Supports SNMP

1.1 Begin by confirming that your device supports the SNMP protocol. Check your device's data sheets, the vendor's website, or the device's configuration. SNMP is a standard protocol and most enterprise-grade devices offer SNMP support to some extent. But in any case we recommend that you double-check.

1.2 Enable SNMP on the target device. For SNMP versions v1 and v2c it is usually sufficient to set an SNMP Community String, but some devices have more complex configurations (allowed managers, etc). Usually the public string is used. This is also the default community string that PRTG will query.

See also How to enable SNMP on your operating System and Basic Requirements for SNMP.

How to enable SNMP on your device

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1.3 If the device does indeed support SNMP and you enabled it, test the functionality with our SNMP Tester. The Read Device Uptime function is a great start. This test must yield a valid response (not 0). Fore a more sophisticated test, a Walk of 1.3.6 will confirm all OIDs that the device can reply to. For more details on this step see How can I test the functionality of my SNMP device? and check the SNMP Tester Manual for more details.

1.4 If SNMP still does not work, please check the hints in SNMP doesn't work! Can somebody out there please help?!

Step 2: Acquire/Download the SNMP MIB File You Need

2.1 For some devices this will be the easy step, in others it will be the hard step. The SNMP MIB is the file that contains the definitions for all OIDs that the device can reply to. It will define what a value is, what name describes that value, and so on.

Note: In some cases, not all OIDs are listed in one single MIB file. Therefore, you might need to provide two (or more) MIB files.

Here are some places you can head to in order to find the SNMP MIB file(s) for your device:

  • The web interface of the target device
  • A default location on the file system of the device
  • The website of the device vendor
  • The vendor's support
  • On the internet as described in Where can I find MIB files for my device?

2.2 The MIB file(s) are provided as a zip-file or as individual downloads usually in .my, .mib, or .txt format. It is important to move/de-compress all the MIB files into one single folder (if you have more than one) so that during the import any MIB dependencies can be resolved.

Step 3: Import the MIB File to PRTG

3.1 The import process is necessary because it converts the MIB file that is written in Abstract Syntax Notation 1 (ASN.1) to a more performance-friendly format that PRTG understands. Use the Paessler MIB Importer and follow the steps below. Fore more details see its manual or this guide How can I import my MIB files into PRTG?

3.2 Import the extracted MIB files by selecting File | Import MIB File | Select File(s) from the main menu of the Paessler MIB Importer. The importer will display statistics regarding the number of imported OIDs and errors (if any).

Import Message Paessler MIB Importer

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3.3 (optional) It is possible to edit/rename properties of the imported MIB file prior to using it within PRTG. This way you can update the name of the sensor or channel to a more friendly/useful description if you need to.

Note: In this step you can review the channel's lookup in the description field. Remember the lookup information when writing a lookup definition (see step 4.4)!

Rename Lookup During Import

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3.4 (optional) It is also possible to make a partial selection of the OIDs to include only the ones you want in the final oidlib file for monitoring with PRTG. This can improve the performance when adding a new SNMP Library sensor and creates less visual clutter to select the required OIDs for monitoring.

Partial Selection During Import

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3.5 Save the resulting oidlib file to any location and copy it to the following program directory on the PRTG core server system:

\PRTG Network Monitor\snmplibs\

You will see the files in this folder when you add a new SNMP Library Sensor.

Step 4: Add the Sensor(s) within PRTG

4.1 Once you have completed the steps above, add a new device to PRTG that points to the target device you want to monitor. You have to provide a name and IP/DNS address. During the creation you may also provide the SNMP credentials that the sensors of this device will use. You can change this also later.

4.2 On the previously created device, click Add | Sensor, select the SNMP Library sensor from the list, and add it. Select the name of the file previously copied into PRTG from the list and select OK.

PRTG now performs a metascan to check which of the OIDs contained in the oidlib file are actually available on the device to monitor and lists them in a table. From the list you can then select for which properties you want to create a sensor:

Metascan During SNMP Library Sensor Creation

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If at this points PRTG hangs or takes a long time to perform the metascan please review this article.

Select the required properties (or all) and click Continue. After a few seconds your PRTG looks like this:

SNMP Library Sensor in PRTG

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4.3 (optional) You can now configure limits for the created sensor channels.

Tip: If you have more devices that you want to monitor exactly that way (using the same OIDs and limits), create a device template. It stores all these settings that you only need to define once. Let PRTG auto-discover the rest of your devices using the defined template and set up monitoring for you.

4.4 Some sensors will display odd values, for example, the status 1 for a hard disk status. Define lookups in this case: You can define lookups to map the meaning of "0", "1", "2", or any other value for that sensor, to more human friendly and better understandable expressions like "Okay", "Error", or "Checking Status".

Once you created/imported a lookup file and configured it, the sensor will report the status like this:

Configure Lookups for the SNMP Library Sensor

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Tip: There's a more detailed lookups guide available in our Knowledge Base: Value interpretation (aka Lookups)

For more information, please review the PRTG User Manual Monitoring via SNMP or contact our support team if you need a helping hand.

Other Related Resources

Best Regards,
Luciano Lingnau [Paessler Support]

Created on Aug 5, 2015 2:03:13 PM by  Luciano Lingnau [Paessler Support]

Last change on May 9, 2019 1:26:23 PM by  Maike Behnsen [Paessler Support]

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Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.