SNMP sensor picker¶

Why a picker¶

Checks stored statically in a profile guess what a device has. That works for homogeneous fleets but fails in reality:

Switches have 16, 24, 28, 48 or 96 ports
Servers have 1, 2, 4, 8 power supplies
Storage systems have 4–60 disks
Custom sensors (door, water, smoke) are never in the standard profile

The picker runs a walk on the target device, lists everything that is actually there, and you tick what should be created as a check.

Opening the picker¶

The picker is part of the device scan: in the checks toolbar of the host detail page, "Device scan" (for every host with a network target, except pure agent hosts) opens a dialog that first tries known vendor checks against the device. There you expand "Search deeper (walk)" — this opens the picker right inside the dialog. The walk uses the host's SNMP version (v1/v2c or v3); if no community is stored, the dialog asks for one first.

Details on the device scan: Host detail page.

Depending on the device the walk takes up to a minute ("Walk running … (can take up to a minute)"). If the collector does not respond for five minutes, the walk ends with Timeout. A single walk reads at most 50,000 rows.

What the walk finds¶

The standard MIBs are evaluated, plus uploaded vendor MIBs (see MIBs) and vendor snippets stored on the profile. Suggestions are grouped:

Group	Source	Suggested checks
Interfaces	IF-MIB	operational state per port (`snmp_oid` on `ifOperStatus`)
Bandwidth	IF-MIB counters (vendor-independent)	"Interface Utilization (highest)" (warning from 90 %), "Interface Errors", per interface "Bandwidth " in Mbit/s (`snmp_bandwidth`, as a rate per second). Wireless interfaces do not count towards the error check; without a reported speed there is no percentage check
Storage / filesystem	HOST-RESOURCES-MIB	fill level per filesystem (`snmp_storage`, warning from 80 %)
CPU cores	HOST-RESOURCES-MIB	load per core
Sensors (temperature, voltage, current, power, fan, humidity, frequency)	ENTITY-SENSOR-MIB	one check per sensor with value and unit
UPS	UPS-MIB	battery status, battery charge and remaining runtime — charge and runtime with a falling limit ("Warn ≤")
Vendor groups	uploaded MIBs / profile snippets	depends on the MIB; the origin of the mapping is shown ("Mapping from the maintained catalog" or "Mapping derived from the labels — a suggestion, please check")

Values returned as timeticks (e.g. sysUpTime) are suggested with the display "Duration from timeticks": the message shows "2d 1h 58m" instead of the raw number. More: SNMP interpretation.

Selection¶

Each group has all / none and a search. Per sensor you see the current value and the suggested thresholds; a "Recommended" mark highlights the sensible suggestions. If the host already measures a value (even under another name, e.g. from the device profile), the suggestion is marked "Present: " and is not pre-selected — adding it again creates a second check.

"Create N as checks" creates the selected sensors as checks on the host — on devices with a collector they run via the collector. With "Also apply selection to the profile" they are also added as checks to the host's device profile and thus to every device with that profile; only a Super Admin may do that, because profiles apply to all tenants.

"Rescan" starts a fresh walk, e.g. after a hardware change.

API¶

Endpoint	Purpose
`POST /api/v1/discovery/snmp-walk`	New walk job
`GET /api/v1/discovery/snmp-walk/{id}`	Status + result
`GET /api/v1/discovery/hosts/{host_id}/snmp-walk/latest`	Latest walk of a host
`POST /api/v1/discovery/snmp-walk/{id}/cancel`	Cancel a walk
`POST /api/v1/discovery/snmp-walk/{id}/apply`	Create the selection as checks

Limits¶

Without uploaded vendor MIBs the walk only covers the standard MIBs — for vendor-specific values see MIBs.
Plain SNMP v1 has no bulk reads; the walk is slower there.