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Snmptrap

SNMP Trap

An SNMP trap is the standard method to send an alert notification to a northbound NMS or to an event correlation system. This transport sends SNMPv2c TRAPs or INFORMs. Each message carries structured varbind data from the alert template. You therefore control the OIDs and the values.

The transport uses the system snmptrap binary. You can configure its path under Settings → External → Binaries → snmptrap.

Requirements

  • Net-SNMP tools installed on the LibreNMS host (snmptrap binary).
  • A MIB file on the LibreNMS host with the trap structure. The LibreNMS MIB (LIBRENMS-NOTIFICATIONS-MIB) is in mibs/librenms/. It covers the default alert template.

Configuration

Setting Default Description
Destination Host — The hostname or IP address of the trap receiver
Destination Port 162 The UDP or TCP port on the receiver
Transport UDP UDP or TCP
Community public The SNMPv2c community string
Trap OID LIBRENMS-NOTIFICATIONS-MIB::defaultAlertEvent The notification OID from the MIB
PDU Type TRAPv2 TRAPv2 is one-way. INFORM is acknowledged
MIB Directory /opt/librenms/mibs/librenms The directory with the MIB files

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 transport reads the message body of the alert template as a sequence of varbind lines. Each line has this form:

OID type value

type is a Net-SNMP type character. s is a string, i is an integer, t is timeticks, and o is an OID. value can be a string in double quotation marks with spaces. A line that starts with # is a comment.

Catch-All Template (LIBRENMS-NOTIFICATIONS-MIB)

Create an alert template with the name SNMP Trap — Default and the body below. Assign it to each transport with 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 MIB directory to the LibreNMS host. Then configure the path:

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

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

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