Home Assistant

SNMP

The snmp sensor platform displays information available through the Simple Network Management Protocol (SNMP). SNMP uses a tree-like hierarchy where each node is an object, and is mainly supported by network-oriented devices such as routers, modems, and printers.

To enable this sensor in your installation, add the following to your configuration.yaml file:

# Example configuration.yaml entry
sensor:
  - platform: snmp
    host: 192.168.1.32
    baseoid: 1.3.6.1.4.1.2021.10.1.3.1

Configuration variables:

  • host (Required): The IP address of your host, eg. 192.168.1.32.
  • baseoid (Required): The OID where the information is located. It’s advised to use the numerical notation.
  • port (Option): The SNMP port of your host. Defaults to 161.
  • community (Optional): The SNMP community which is set for the device. Most devices have a default community set to public with read-only permission (which is sufficient).
  • version (Optional) version of SNMP protocol, 1 or 2c. Defaults to 1. Version 2c is needed to read data from 64-bit counters.
  • name (Optional): Name of the SNMP sensor.
  • unit_of_measurement (Optional): Defines the unit of measurement of the sensor, if any.
  • value_template (Optional): Defines a template to parse the value.
  • accept_errors (Optional): Determines whether the sensor should start and keep working even if the SNMP host is unreachable or not responding. This allows the sensor to be initialized properly even if, for example, your printer is not on when you start Home Assistant. Defaults to false.
  • default_value (Optional): Determines what value the sensor should take if accept_errors is set and the host is unreachable or not responding. If not set, the sensor will have value unknown in case of errors.

Finding OIDs

OIDs may vary on different systems because they are vendor-specific. Beside the device’s manual, the OID Repository is a good place to start if you are looking for OIDs. As an example, the following OIDs are for the load of a Linux systems.

  • 1 minute Load: 1.3.6.1.4.1.2021.10.1.3.1
  • 5 minute Load: 1.3.6.1.4.1.2021.10.1.3.2
  • 15 minute Load: 1.3.6.1.4.1.2021.10.1.3.3

There is a large amount of tools available to work with SNMP. snmpwalk let you easily retrieve the value of a OID.

$ snmpwalk -Os -c public -v 2c 192.168.1.32 1.3.6.1.4.1.2021.10.1.3.1
laLoad.1 = STRING: 0.19

Examples

Printer uptime minutes

According to the most common SNMP standard, the uptime of a device is accessible under OID 1.3.6.1.2.1.1.3.0. The value represented using a format called TimeTicks, in units of hundredth of a second.

To create a sensor that displays the uptime for your printer in minutes, you can use this configuration:

# Example configuration.yaml entry
sensor:
  - platform: snmp
    name: 'Printer uptime'
    host: 192.168.2.21
    baseoid: 1.3.6.1.2.1.1.3.0
    accept_errors: true
    unit_of_measurement: 'minutes'
    value_template: '{{((value | int) / 6000) | int}}'

The accept_errors option will allow the sensor to work even if the printer is not on when Home Assistant is first started: the sensor will just display a - instead of a minute count.

The value_template option converts the original value to minutes.