banshee/network-collection/network/snmp/sensors

Hardware sensors of a network device, by SNMP

Returns, for each hardware sensor of a switch, a router or a firewall, its measure in its unit (temperature, fan speed, voltage, current, power) and the state the device gives it. Five watches are offered, each one set on the probe.

How it works

The collector reads entPhySensorTable (ENTITY-SENSOR-MIB, RFC 3433), the standard table of the sensors of a device, whatever its brand, and names each sensor by entPhysicalName (ENTITY-MIB), the name the device gives the part it measures.

The measure is entPhySensorValue, brought to its unit by entPhySensorScale (milli, units, kilo…) and entPhySensorPrecision (the number of decimals): a sensor reading 42500 milli-degrees with no decimal returns 42.5 °C.
Each sensor goes to the output of its type: celsius to temperature, rpm to fan-speed, voltsAC and voltsDC to voltage, amperes to current, watts to power. A sensor of another type (humidity, frequency, a true/false) returns its state only.
The state is entPhySensorOperStatus in words: ok, unavailable, nonoperational. The measure of a sensor that is not ok is not returned: it means nothing.
A sensor without a name takes its index (sensor 1012); two sensors of the same name each keep their own, the second carrying its index.
A device that serves no sensor stops the collector as misconfigured: never a green light without a measure.

The collector only reads: SNMP sends nothing but reads.

Prerequisites

The SNMP agent of the device enabled, reachable from the poller (UDP 161), its access restricted to the poller.
An agent that implements ENTITY-SENSOR-MIB; the view granted to the poller includes entitySensorMIB (.1.3.6.1.2.1.99) and entPhysicalName (.1.3.6.1.2.1.47.1.1.1.1.7).
Read-only access, SNMPv2c or SNMPv3, set on the host or one of its folders (protocol:snmp:* variables).
Versions: any device and any version whose agent serves the standard table. A brand that keeps its sensors in its own MIB only is read by the collector of that brand (network/cisco/snmp/ios/environment, network/mikrotik/snmp/health).

Outputs

Name	Label	Unit	Per instance
`temperature`	Temperature	°C	yes, per sensor
`fan-speed`	Fan speed	rpm	yes, per sensor
`voltage`	Voltage	V	yes, per sensor
`current`	Current	A	yes, per sensor
`power`	Power	W	yes, per sensor
`status`	Sensor state	—	yes, per sensor

Watches

Name	Title	Kind	Defaults	Checked by default
`hot`	High temperature	above a threshold, on `temperature`	warning above 70 °C, critical above 85 °C, for 3 runs	yes
`fan-stopped`	Fan stopped	below a threshold, on `fan-speed`	critical below 1 rpm, for 2 runs	yes
`failed`	Sensor failed	state to avoid, on `status`	critical on `nonoperational`	yes
`voltage-low`	Low voltage	below a threshold, on `voltage`	no threshold: each rail has its own, set it on the probe	no
`missing`	Missing sensor	expected instances, on `status`	no sensor named: it raises nothing until names are set on the probe	no

Limits

The temperature thresholds, 70 °C and 85 °C, are generic defaults, taken from no maker's documentation: adapt them to the hardware on the probe. An optical transceiver runs cooler than a switching chip; leave out the sensors that do not count in the selection.
The thresholds the device itself keeps (entPhySensorThreshold is not in RFC 3433, only in vendor extensions) are not read.
Which devices serve ENTITY-SENSOR-MIB, and with which names, is not verified here without a device: run the probe once and read its sensors.