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Snmptrap

SNMP Trap

SNMP traps are the standard way to push alert notifications to a northbound NMS or event correlation system. This transport sends SNMPv2c TRAPs or INFORMs carrying structured varbind data that is fully defined by the alert template — giving you complete control over which OIDs and values are included.

The transport uses the system snmptrap binary (configurable under Settings → External → Binaries → snmptrap).

Requirements

  • Net-SNMP tools installed on the LibreNMS host (snmptrap binary).
  • A MIB file accessible on the LibreNMS host describing the trap structure. The LibreNMS-contributed MIB (LIBRENMS-NOTIFICATIONS-MIB) is shipped under mibs/librenms/ and covers the default alert template.

Configuration

Setting Default Description
Destination Host — Hostname or IP of the trap receiver
Destination Port 162 UDP/TCP port on the receiver
Transport UDP UDP or TCP
Community public SNMPv2c community string
Trap OID LIBRENMS-NOTIFICATIONS-MIB::defaultAlertEvent Notification OID defined in the MIB
PDU Type TRAPv2 TRAPv2 (one-way) or INFORM (acknowledged)
MIB Directory /opt/librenms/mibs/librenms Directory containing the MIB file(s)

Example:

Config Example
Destination Host noc.example.com
Destination Port 162
Transport UDP
Community monitoring
Trap OID LIBRENMS-NOTIFICATIONS-MIB::defaultAlertEvent
PDU Type TRAPv2
MIB Directory /opt/librenms/mibs/librenms

Alert Templates

The message body produced by the alert template is parsed as a sequence of varbind lines, each with the form:

OID type value

where type is a Net-SNMP type character (s = string, i = integer, t = timeticks, o = OID, …) and value may be a double-quoted string containing spaces. Lines beginning with # are treated as comments.

Catch-All Template (LIBRENMS-NOTIFICATIONS-MIB)

Create an alert template with the name SNMP Trap — Default and the following body. Assign it to transports that reference LIBRENMS-NOTIFICATIONS-MIB::defaultAlertEvent.

defaultAlertTitle s "{{ $alert->title }}"
defaultAlertID i {{ $alert->id }}
defaultAlertEventID i {{ $alert->uid }}
defaultAlertState i {{ $alert->state }}
defaultAlertSeverity s "{{ $alert->severity }}"
defaultAlertRuleID i {{ $alert->rule_id }}
defaultAlertRuleName s "{{ $alert->name }}"
defaultAlertProcedure s "{{ $alert->proc }}"
defaultAlertTimestamp s "{{ $alert->timestamp }}"
@if ($alert->state == 0)
defaultAlertTimeElapsed s "{{ $alert->elapsed }}"
@endif
defaultAlertDeviceID i {{ $alert->device_id }}
defaultAlertDevHostname s "{{ $alert->hostname }}"
defaultAlertDevSysName s "{{ $alert->sysName }}"
defaultAlertDevMgmtIP s "{{ $alert->ip }}"
defaultAlertDevOS s "{{ $alert->os }}"
defaultAlertDevType s "{{ $alert->type }}"
defaultAlertDevHardware s "{{ $alert->hardware }}"
defaultAlertDevVersion s "{{ $alert->version }}"
defaultAlertDevLocation s "{{ $alert->location }}"
defaultAlertDevUptime t {{ $alert->uptime }}
defaultAlertDevShortUptime s "{{ $alert->uptime_short }}"
defaultAlertACKNotes s "{{ $alert->alert_notes }}"
@if ($alert->faults)
@foreach ($alert->faults as $key => $value)
defaultAlertFaultDetail.{{ $key }} s "{{ $value['string'] }}"
@endforeach
@endif

MIB Installation

Copy the desired MIB directory to the LibreNMS host and configure the path:

# LibreNMS MIB (default)
cp -r /opt/librenms/mibs/librenms /opt/librenms/mibs/librenms

To make the MIB globally available to Net-SNMP tools:

cp /opt/librenms/mibs/librenms/LIBRENMS-NOTIFICATIONS-MIB \
   /usr/share/snmp/mibs/