Evaluating NOTIFICATION-TYPE
****************************

SNMP SMI defines notifications as a TRAP or INFORM PDU containing the
indication of type (snmpTrapOID) and a set of MIB variables (Managed
Objects Instances) fetched from Agent's MIB at the moment of
notification.

Consequently, sending specific NOTIFICATION-TYPE implies including
certain set of OIDs into PDU. PySNMP offers this facility through
NotificationType class.


Sending notification with OBJECT's
==================================

Send SNMP TRAP notification using the following options:

* SNMPv2c

* with community name 'public'

* over IPv4/UDP

* send TRAP notification

* to a Manager at 104.236.166.95:162

* with TRAP ID IF-MIB::ifLink as MIB symbol

The IF-MIB::ifLink NOTIFICATION-TYPE implies including four other var-
binds into the notification message describing the incident occurred.
These var-binds are: IF-MIB::ifIndex."x" IF-MIB::ifAdminStatus."x" IF-
MIB::ifOperStatus."x" IF-MIB::ifDescr."x"

Where "x" is MIB table index (instance index).

Functionally similar to:

   $ snmptrap -v2c -c public 104.236.166.95 0 1.3.6.1.6.3.1.1.5.3 IF-MIB::ifIndex."1" IF-MIB::ifAdminStatus."1" IF-MIB::ifOperStatus."1" IF-MIB::ifDescr."1"

   from pysnmp.entity import engine, config
   from pysnmp.carrier.asyncore.dgram import udp
   from pysnmp.entity.rfc3413 import ntforg
   from pysnmp.smi import rfc1902, view

   #
   # Here we fill in some values for Managed Objects Instances (invoked
   # later while building TRAP message) by NOTIFICATION-TYPE macro evaluation.
   # In real Agent app, these values should already be initialized during
   # Agent runtime.
   #
   instanceIndex = (1,)
   objects = {
       ('IF-MIB', 'ifIndex'): instanceIndex[0],
       ('IF-MIB', 'ifAdminStatus'): 'up',
       ('IF-MIB', 'ifOperStatus'): 'down',
       ('IF-MIB', 'ifDescr'): 'eth0'
   }

   # Create SNMP engine instance
   snmpEngine = engine.SnmpEngine()

   # MIB view controller is used for MIB lookup purposes
   mibViewController = view.MibViewController(snmpEngine.getMibBuilder())

   # SecurityName <-> CommunityName mapping
   config.addV1System(snmpEngine, 'my-area', 'public', transportTag='all-my-managers')

   # Specify security settings per SecurityName (SNMPv2c -> 1)
   config.addTargetParams(snmpEngine, 'my-creds', 'my-area', 'noAuthNoPriv', 1)

   # Setup transport endpoints and bind it with security settings yielding
   # a target name:

   # UDP/IPv4
   config.addTransport(
       snmpEngine,
       udp.domainName,
       udp.UdpSocketTransport().openClientMode()
   )
   config.addTargetAddr(
       snmpEngine, 'my-nms-1',
       udp.domainName, ('104.236.166.95', 162),
       'my-creds',
       tagList='all-my-managers'
   )

   # Specify what kind of notification should be sent (TRAP or INFORM),
   # to what targets (chosen by tag) and what filter should apply to
   # the set of targets (selected by tag)
   config.addNotificationTarget(
       snmpEngine, 'my-notification', 'my-filter', 'all-my-managers', 'trap'
   )

   # Allow NOTIFY access to Agent's MIB by this SNMP model (2), securityLevel
   # and SecurityName
   config.addContext(snmpEngine, '')
   config.addVacmUser(snmpEngine, 2, 'my-area', 'noAuthNoPriv', (), (), (1, 3, 6))

   # *** SNMP engine configuration is complete by this line ***

   # Create Notification Originator App instance. 
   ntfOrg = ntforg.NotificationOriginator()

   # Build and submit notification message to dispatcher
   ntfOrg.sendVarBinds(
       snmpEngine,
       'my-notification',  # notification targets
       None, '',  # contextEngineId, contextName
       rfc1902.NotificationType(
           rfc1902.ObjectIdentity('IF-MIB', 'linkUp'),
           instanceIndex=instanceIndex,
           objects=objects
       ).resolveWithMib(mibViewController)
   )

   print('Notification is scheduled to be sent')

   # Run I/O dispatcher which would send pending message and process response
   snmpEngine.transportDispatcher.runDispatcher()

"Download" script.

See also: library reference.
