Agent-side MIB implementations

Implementing scalar MIB objects

Listen and respond to SNMP GET/SET/GETNEXT/GETBULK queries with the following options:

  • SNMPv2c
  • with SNMP community “public”
  • serving custom Managed Object Instance defined within this script
  • allow read access only to the subtree where the custom MIB object resides
  • over IPv4/UDP, listening at 127.0.0.1:161

The following Net-SNMP commands will walk this Agent:

$ snmpwalk -v2c -c public 127.0.0.1 .1.3.6
import sys
from pysnmp.entity import engine, config
from pysnmp.entity.rfc3413 import cmdrsp, context
from pysnmp.carrier.asyncore.dgram import udp
from pysnmp.proto.api import v2c

# Create SNMP engine
snmpEngine = engine.SnmpEngine()

# Transport setup

# UDP over IPv4
config.addTransport(
    snmpEngine,
    udp.domainName,
    udp.UdpTransport().openServerMode(('127.0.0.1', 161))
)

# SNMPv2c setup

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

# Allow read MIB access for this user / securityModels at VACM
config.addVacmUser(snmpEngine, 2, 'my-area', 'noAuthNoPriv', (1, 3, 6, 5))

# Create an SNMP context
snmpContext = context.SnmpContext(snmpEngine)

# --- create custom Managed Object Instance ---

mibBuilder = snmpContext.getMibInstrum().getMibBuilder()

MibScalar, MibScalarInstance = mibBuilder.importSymbols(
    'SNMPv2-SMI', 'MibScalar', 'MibScalarInstance'
)


class MyStaticMibScalarInstance(MibScalarInstance):
    # noinspection PyUnusedLocal,PyUnusedLocal
    def getValue(self, name, idx):
        return self.getSyntax().clone(
            'Python %s running on a %s platform' % (sys.version, sys.platform)
        )


mibBuilder.exportSymbols(
    '__MY_MIB', MibScalar((1, 3, 6, 5, 1), v2c.OctetString()),
    MyStaticMibScalarInstance((1, 3, 6, 5, 1), (0,), v2c.OctetString())
)

# --- end of Managed Object Instance initialization ----

# Register SNMP Applications at the SNMP engine for particular SNMP context
cmdrsp.GetCommandResponder(snmpEngine, snmpContext)
cmdrsp.NextCommandResponder(snmpEngine, snmpContext)
cmdrsp.BulkCommandResponder(snmpEngine, snmpContext)

# Register an imaginary never-ending job to keep I/O dispatcher running forever
snmpEngine.transportDispatcher.jobStarted(1)

# Run I/O dispatcher which would receive queries and send responses
try:
    snmpEngine.transportDispatcher.runDispatcher()
except:
    snmpEngine.transportDispatcher.closeDispatcher()
    raise

Download script.

Implementing conceptual table

Listen and respond to SNMP GET/SET/GETNEXT/GETBULK queries with the following options:

  • SNMPv2c
  • with SNMP community “public”
  • define a simple SNMP Table within a newly created EXAMPLE-MIB
  • pre-populate SNMP Table with a single row of values
  • allow read access only to the subtree where example SNMP Table resides
  • over IPv4/UDP, listening at 127.0.0.1:161

The following Net-SNMP commands will populate and walk a table:

$ snmpset -v2c -c public 127.0.0.1 1.3.6.6.1.5.2.97.98.99 s “my value”
$ snmpset -v2c -c public 127.0.0.1 1.3.6.6.1.5.4.97.98.99 i 4
$ snmpwalk -v2c -c public 127.0.0.1 1.3.6

...while the following command will destroy the same row

$ snmpset -v2c -c public 127.0.0.1 1.3.6.6.1.5.4.97.98.99 i 6
$ snmpwalk -v2c -c public 127.0.0.1 1.3.6
from pysnmp.entity import engine, config
from pysnmp.entity.rfc3413 import cmdrsp, context
from pysnmp.carrier.asyncore.dgram import udp
from pysnmp.proto.api import v2c

# Create SNMP engine
snmpEngine = engine.SnmpEngine()

# Transport setup

# UDP over IPv4
config.addTransport(
    snmpEngine,
    udp.domainName,
    udp.UdpTransport().openServerMode(('127.0.0.1', 161))
)

# SNMPv2c setup

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

# Allow read MIB access for this user / securityModels at VACM
config.addVacmUser(snmpEngine, 2, 'my-area', 'noAuthNoPriv', (1, 3, 6, 6), (1, 3, 6, 6))

# Create an SNMP context
snmpContext = context.SnmpContext(snmpEngine)

# --- define custom SNMP Table within a newly defined EXAMPLE-MIB ---

mibBuilder = snmpContext.getMibInstrum().getMibBuilder()

(MibTable,
 MibTableRow,
 MibTableColumn,
 MibScalarInstance) = mibBuilder.importSymbols(
    'SNMPv2-SMI',
    'MibTable',
    'MibTableRow',
    'MibTableColumn',
    'MibScalarInstance'
)

RowStatus, = mibBuilder.importSymbols('SNMPv2-TC', 'RowStatus')

mibBuilder.exportSymbols(
    '__EXAMPLE-MIB',
    # table object
    exampleTable=MibTable((1, 3, 6, 6, 1)).setMaxAccess('readcreate'),
    # table row object, also carries references to table indices
    exampleTableEntry=MibTableRow((1, 3, 6, 6, 1, 5)).setMaxAccess('readcreate').setIndexNames((0, '__EXAMPLE-MIB', 'exampleTableColumn1')),
    # table column: string index
    exampleTableColumn1=MibTableColumn((1, 3, 6, 6, 1, 5, 1), v2c.OctetString()).setMaxAccess('readcreate'),
    # table column: string value
    exampleTableColumn2=MibTableColumn((1, 3, 6, 6, 1, 5, 2), v2c.OctetString()).setMaxAccess('readcreate'),
    # table column: integer value with default
    exampleTableColumn3=MibTableColumn((1, 3, 6, 6, 1, 5, 3), v2c.Integer32(123)).setMaxAccess('readcreate'),
    # table column: row status
    exampleTableStatus=MibTableColumn((1, 3, 6, 6, 1, 5, 4), RowStatus('notExists')).setMaxAccess('readcreate')
)

# --- end of custom SNMP table definition, empty table now exists ---

# --- populate custom SNMP table with one row ---

(exampleTableEntry,
 exampleTableColumn2,
 exampleTableColumn3,
 exampleTableStatus) = mibBuilder.importSymbols(
    '__EXAMPLE-MIB',
    'exampleTableEntry',
    'exampleTableColumn2',
    'exampleTableColumn3',
    'exampleTableStatus'
)
rowInstanceId = exampleTableEntry.getInstIdFromIndices('example record one')
mibInstrumentation = snmpContext.getMibInstrum()
mibInstrumentation.writeVars(
    ((exampleTableColumn2.name + rowInstanceId, 'my string value'),
     (exampleTableColumn3.name + rowInstanceId, 123456),
     (exampleTableStatus.name + rowInstanceId, 'createAndGo'))
)

# --- end of SNMP table population ---

# Register SNMP Applications at the SNMP engine for particular SNMP context
cmdrsp.GetCommandResponder(snmpEngine, snmpContext)
cmdrsp.SetCommandResponder(snmpEngine, snmpContext)
cmdrsp.NextCommandResponder(snmpEngine, snmpContext)
cmdrsp.BulkCommandResponder(snmpEngine, snmpContext)

# Register an imaginary never-ending job to keep I/O dispatcher running forever
snmpEngine.transportDispatcher.jobStarted(1)

# Run I/O dispatcher which would receive queries and send responses
try:
    snmpEngine.transportDispatcher.runDispatcher()
except:
    snmpEngine.transportDispatcher.closeDispatcher()
    raise

Download script.

Serve non-default MIB tree

Listen and respond to SNMP GET/SET/GETNEXT/GETBULK queries with the following options:

  • SNMPv3
  • with USM username usr-md5-none
  • using alternative set of Managed Objects addressed by contextEngineId: 8000000001020304, contextName: my-context
  • allow access to SNMPv2-MIB objects (1.3.6.1.2.1)
  • over IPv4/UDP, listening at 127.0.0.1:161

Either of the following Net-SNMP commands will walk this Agent:

$ snmpwalk -v3 -u usr-md5-none -l authNoPriv -A authkey1 -E 8000000001020304 -n my-context 127.0.0.1 .1.3.6
$ snmpwalk -v3 -u usr-md5-none -l authNoPriv -A authkey1 -E 8000000001020304 127.0.0.1 .1.3.6
from pysnmp.entity import engine, config
from pysnmp.entity.rfc3413 import cmdrsp, context
from pysnmp.carrier.asyncore.dgram import udp
from pysnmp.smi import instrum, builder
from pysnmp.proto.api import v2c

# Create SNMP engine
snmpEngine = engine.SnmpEngine()

# Transport setup

# UDP over IPv4
config.addTransport(
    snmpEngine,
    udp.domainName,
    udp.UdpTransport().openServerMode(('127.0.0.1', 161))
)

# SNMPv3/USM setup

# user: usr-md5-none, auth: MD5, priv NONE
config.addV3User(
    snmpEngine, 'usr-md5-none',
    config.usmHMACMD5AuthProtocol, 'authkey1'
)

# Allow full MIB access for each user at VACM
config.addVacmUser(snmpEngine, 3, 'usr-md5-none', 'authNoPriv', (1, 3, 6, 1, 2, 1), (1, 3, 6, 1, 2, 1))

# Create an SNMP context with ContextEngineId = 8000000001020304
snmpContext = context.SnmpContext(
    snmpEngine, contextEngineId=v2c.OctetString(hexValue='8000000001020304')
)

# Create an [empty] set of Managed Objects (MibBuilder), pass it to
# Management Instrumentation Controller and register at SNMP Context
# under ContextName 'my-context'
snmpContext.registerContextName(
    v2c.OctetString('my-context'),  # Context Name
    instrum.MibInstrumController(builder.MibBuilder())  # Managed Objects
)

# Register SNMP Applications at the SNMP engine for particular SNMP context
cmdrsp.GetCommandResponder(snmpEngine, snmpContext)
cmdrsp.SetCommandResponder(snmpEngine, snmpContext)
cmdrsp.NextCommandResponder(snmpEngine, snmpContext)
cmdrsp.BulkCommandResponder(snmpEngine, snmpContext)

# Register an imaginary never-ending job to keep I/O dispatcher running forever
snmpEngine.transportDispatcher.jobStarted(1)

# Run I/O dispatcher which would receive queries and send responses
try:
    snmpEngine.transportDispatcher.runDispatcher()
except:
    snmpEngine.transportDispatcher.closeDispatcher()
    raise

Download script.

Custom MIB Controller

Listen and respond to SNMP GET/SET/GETNEXT/GETBULK queries with the following options:

  • SNMPv3
  • with USM username usr-none-none
  • using alternative set of Managed Objects addressed by contextName: my-context
  • allow access to SNMPv2-MIB objects (1.3.6.1.2.1)
  • over IPv4/UDP, listening at 127.0.0.1:161

The following Net-SNMP command will send GET request to this Agent:

$ snmpget -v3 -u usr-none-none -l noAuthNoPriv -n my-context -Ir 127.0.0.1 sysDescr.0
from pysnmp.entity import engine, config
from pysnmp.entity.rfc3413 import cmdrsp, context
from pysnmp.carrier.asyncore.dgram import udp
from pysnmp.smi import instrum
from pysnmp.proto.api import v2c

# Create SNMP engine
snmpEngine = engine.SnmpEngine()

# Transport setup

# UDP over IPv4
config.addTransport(
    snmpEngine,
    udp.domainName,
    udp.UdpTransport().openServerMode(('127.0.0.1', 161))
)

# SNMPv3/USM setup

# user: usr-none-none, auth: NONE, priv NONE
config.addV3User(
    snmpEngine, 'usr-none-none'
)

# Allow full MIB access for each user at VACM
config.addVacmUser(snmpEngine, 3, 'usr-none-none', 'noAuthNoPriv', (1, 3, 6, 1, 2, 1), (1, 3, 6, 1, 2, 1))

# Create an SNMP context
snmpContext = context.SnmpContext(snmpEngine)


# Very basic Management Instrumentation Controller without
# any Managed Objects attached. It supports only GET's and
# always echos request var-binds in response.
class EchoMibInstrumController(instrum.AbstractMibInstrumController):
    def readVars(self, varBinds, acInfo=(None, None)):
        return [(ov[0], v2c.OctetString('You queried OID %s' % ov[0])) for ov in varBinds]


# Create a custom Management Instrumentation Controller and register at
# SNMP Context under ContextName 'my-context'
snmpContext.registerContextName(
    v2c.OctetString('my-context'),  # Context Name
    EchoMibInstrumController()  # Management Instrumentation
)

# Register GET&SET Applications at the SNMP engine for a custom SNMP context
cmdrsp.GetCommandResponder(snmpEngine, snmpContext)
cmdrsp.SetCommandResponder(snmpEngine, snmpContext)

# Register an imaginary never-ending job to keep I/O dispatcher running forever
snmpEngine.transportDispatcher.jobStarted(1)

# Run I/O dispatcher which would receive queries and send responses
try:
    snmpEngine.transportDispatcher.runDispatcher()
except:
    snmpEngine.transportDispatcher.closeDispatcher()
    raise

Download script.

See also: library reference.