PRTG Manual: Choosing the Right SNMP Sensor

The Simple Network Management Protocol (SNMP) generally requires little configuration once it is set up. Many network devices support it and you can monitor many parameters with it. PRTG provides you with various SNMP sensors. These sensors range from monitoring general parameters to very specific parameters. Choosing the right sensor for SNMP monitoring that gives you the desired hardware parameters is a decision that depends on several factors: the type of hardware you have, what values you want to monitor, and a few others.

Check SNMP Capability

Make sure that each device that you want to monitor supports SNMP, and that SNMP is enabled. You can find out whether a device supports SNMP by either going to the vendor’s website or checking that it is enabled in the configuration of the device.

i_toolsIf you are uncertain whether SNMP is enabled on the target device and works, we recommend that you try SNMP Tester. You can scan for uptime to perform a basic check for SNMP availability of the target device.

Setup Checklist

  1. Enable SNMP on the device.
  2. In the security settings of the device, allow SNMP access for the PRTG core server system.
  3. Allow User Datagram Protocol (UDP) packages to be sent bidirectionally from the PRTG core server to the device.
  4. SNMP requires the use of UDP ports >1023 to the PRTG client side. This is important for your firewall settings.
  5. Ensure that the firmware of the device is up to date.
  6. Select the appropriate SNMP protocol.

i_round_blueIt is important to know which SNMP version you have to select, because if it is not supported by the server or device you want to monitor, you receive an error message.

i_square_cyanFor more information, see the Knowledge Base: My SNMP sensors don’t work. What can I do?.

SNMP Monitoring Overview

SNMP Monitoring Overview

Vendor-specific SNMP Sensors

PRTG offers many vendor-specific SNMP sensors for some common vendors. These sensors are programmed to match the respective end devices. There are also workarounds for known vendor implementation issues, for example, if SNMP has not been fully implemented on an end device according to the RFCs. Here, our vendor-specific sensors still automatically receive the most important values.

Supported Vendors

  • APC
  • Buffalo
  • Cisco
  • Dell
  • Fujitsu
  • HP
  • HPE
  • IBM
  • Jacarta
  • Juniper
  • LenovoEMC
  • NetApp
  • Nutanix
  • Poseidon
  • QNAP
  • SonicWall
  • Synology

i_square_cyanFor more information, see the Knowledge Base: What SNMP sensors does PRTG offer?.

Generic SNMP Sensors

PRTG offers several generic sensors that work with almost every device that supports SNMP, the corresponding Management Information Base (MIB) file and OIDs, and it correctly implements the respective RFCs. The standard SNMP libraries of PRTG include predefined, common values for the generic SNMP sensors. You can monitor the following parameters with the generic sensors.

Sensor

What It Monitors

SNMP CPU Load sensor

System load via SNMP

SNMP Disk Free sensor

Free disk space on a logical disk via SNMP

SNMP Hardware Status sensor

Status of a hardware component of a server via SNMP

SNMP Memory sensor

Memory usage of a system via SNMP

SNMP Printer sensor

Various types of printers via SNMP

SNMP RMON sensor

Traffic on a device using RMON via SNMP

SNMP System Uptime sensor

Uptime of a device via SNMP

SNMP Traffic sensor

Traffic on a device via SNMP

SNMP Trap Receiver sensor

SNMP traps

Operating System-based SNMP Sensors

PRTG also offers several operating system-based SNMP sensors that extend your SNMP monitoring. You can monitor the following parameters with these sensors.

Sensor

Description

SNMP Linux Disk Free sensor

Free space on disks of a Linux/Unix system via SNMP

SNMP Linux Load Average sensor

System load average of a Linux/Unix system via SNMP

SNMP Linux Meminfo sensor

Memory usage of a Linux/Unix system via SNMP

SNMP Linux Physical Disk sensor

I/O on disks of a Linux/Unix system via SNMP

SNMP Windows Service sensor

Windows service via SNMP

Custom SNMP Sensors

PRTG also offers custom SNMP sensors. The monitoring capabilities of these sensors extend the scope of the generic sensors. With custom sensors, you can show certain values that are not included in the standard libraries of PRTG. With these sensors, you can monitor most devices that support SNMP and for which PRTG does not have native sensors. Basically, you only need to find out the required OIDs for the desired device readings, for example, in the vendor’s documentation for your hardware device.

i_square_cyanFor more information, see the Knowledge Base: How do I find out which OID I need for an SNMP Custom sensor?.

Sensor

Description

SNMP Custom sensor

The SNMP Custom sensor monitors a single parameter that is returned by a specific object identifier (OID) via the Simple Network Management Protocol (SNMP).

Value types include the expected numeric type of the results at the specified OID: You can choose from

  • Absolute (unsigned integer): for integer values such as 10 or 120
  • Absolute (signed integer): for integer values such as -12 or 120 (negative values supported)
  • Absolute (float): for float values such as -5.80 or 8.23 (with decimal places)
  • Delta (counter): PRTG calculates the difference between the previous and the current value.

i_playFor more information, see this video tutorial SNMP Custom sensor and SNMP Custom Library sensor on our website.

SNMP Custom Advanced sensor

The SNMP Custom Advanced sensor monitors numeric values returned for object identifiers (OID) via the Simple Network Management Protocol (SNMP).

This sensor monitors very similarly to the regular SNMP Custom sensor, with the advantage of being able to poll up to 10 specific OIDs with a single sensor. For each OID, you can define a name, OID, expected type, and the unit to be displayed. The possible value types are the same as with the SNMP Custom sensor.

SNMP Custom String sensor

The SNMP Custom String sensor monitors a string returned by a specific object identifier (OID) via the Simple Network Management Protocol (SNMP). It can check for keywords. If you want to set limits to the channel value, you can also extract a numeric value contained in the string.

Hexadecimal-encoded strings can also be decoded as MAC addresses or IP addresses. The sensor can check for keywords via plain text or regular expression (regex) or you can use a regex to extract a numeric value from the string that can be evaluated later for additional alerts.

i_square_cyanSee section Number Extraction with Regular Expression for an example.

SNMP Custom String Lookup sensor

The SNMP Custom String Lookup sensor monitors a string that a specific object identifier (OID) returns via the Simple Network Management Protocol (SNMP). It can map the string directly to a sensor status by using a defined lookup file.

i_square_cyanBasically, this sensor does a "reverse lookup". You have to define all potential return strings in the lookup file as text values, each in one lookup entry. Graphs and data tables show the value to which the string is mapped, usually an integer (lookup type SingleInt). For more information, see section Example.

SNMP Custom Table sensor

The SNMP Custom Table sensor monitors entries from a table that is provided via the Simple Network Management Protocol (SNMP). You can create one new sensor per table row. For each sensor, you can define up to ten channels. Each channel shows the value of one defined table column.

Vendors use tables when there are multiple instances of the same object (for example, memory, disks). The sensor recognizes a table via a meta-scan and lets you configure the indexes (interfaces) that you want to monitor.

i_square_cyanFor more details, see the Knowledge Base: What can I monitor with the SNMP Custom Table sensor?.

SNMP Library sensor

The SNMP Library sensor uses a Management Information Base (MIB) file to create sensors that monitor a device via the Simple Network Management Protocol (SNMP).

More

i_square_blueKNOWLEDGE BASE

My SNMP sensors don’t work. What can I do?

What SNMP sensors does PRTG offer?

How do I find out which OID I need for an SNMP Custom sensor?

What can I monitor with the SNMP Custom Table sensor?

How do SNMP, MIBs and OIDs work?

How can I import my MIB files into PRTG?

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

 

i_playVIDEO TUTORIAL

SNMP Custom sensor and SNMP Custom Library sensor