Agent side

Implementing MIB objects

This script explains how SNMP Agent application could model real-world data as Managed Objects defined in MIB.

from pysnmp.smi import builder

# MIB Builder is normally pre-created by SNMP engine
mibBuilder = builder.MibBuilder()

#
# This may be done in a stand-alone file and then loaded up
# by SNMP Agent
#

# A base class for a custom Managed Object
MibScalarInstance, = mibBuilder.importSymbols(
    'SNMPv2-SMI', 'MibScalarInstance'
)

# Managed object specification
sysLocation, = mibBuilder.importSymbols('SNMPv2-MIB', 'sysLocation')


# Custom Managed Object
class MySysLocationInstance(MibScalarInstance):
    # noinspection PyUnusedLocal
    def readGet(self, varBind, **context):
        # Just return a custom value
        return varBind[0], self.syntax.clone('The Leaky Cauldron')


sysLocationInstance = MySysLocationInstance(
    sysLocation.name, (0,), sysLocation.syntax
)

# Register Managed Object with a MIB tree
mibBuilder.exportSymbols(
    # '__' prefixed MIB modules take precedence on indexing
    '__MY-LOCATION-MIB', sysLocationInstance=sysLocationInstance
)

if __name__ == '__main__':
    #
    # This is what is done internally by Agent.
    #
    from pysnmp.smi import instrum, exval

    mibInstrum = instrum.MibInstrumController(mibBuilder)

    print('Remote manager read access to MIB instrumentation (table walk)')

    varBinds = [((), None)]

    while True:
        varBinds = mibInstrum.readNextVars(*varBinds)
        oid, val = varBinds[0]
        if exval.endOfMib.isSameTypeWith(val):
            break
        print(oid, val.prettyPrint())

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Agent operations on MIB

This script explains how SNMP Agent application manipulates its MIB possibly triggered by SNMP Manager’s commands.

# SNMP agent backend e.g. Agent access to Managed Objects
from pysnmp.smi import builder, instrum, exval

print('Loading MIB modules...'),
mibBuilder = builder.MibBuilder().loadModules(
    'SNMPv2-MIB', 'SNMP-FRAMEWORK-MIB', 'SNMP-COMMUNITY-MIB'
)
print('done')

print('Building MIB tree...'),
mibInstrum = instrum.MibInstrumController(mibBuilder)
print('done')

print('Building table entry index from human-friendly representation...'),
snmpCommunityEntry, = mibBuilder.importSymbols(
    'SNMP-COMMUNITY-MIB', 'snmpCommunityEntry'
)
instanceId = snmpCommunityEntry.getInstIdFromIndices('my-router')
print('done')

print('Create/update SNMP-COMMUNITY-MIB::snmpCommunityEntry table row: ')
varBinds = mibInstrum.writeVars(
    (snmpCommunityEntry.name + (2,) + instanceId, 'mycomm'),
    (snmpCommunityEntry.name + (3,) + instanceId, 'mynmsname'),
    (snmpCommunityEntry.name + (7,) + instanceId, 'volatile')
)
for oid, val in varBinds:
    print('%s = %s' % ('.'.join([str(x) for x in oid]), not val.isValue and 'N/A' or val.prettyPrint()))
print('done')

print('Read whole MIB (table walk)')
varBinds = [((), None)]
while True:
    varBinds = mibInstrum.readNextVars(*varBinds)
    oid, val = varBinds[0]
    if exval.endOfMib.isSameTypeWith(val):
        break
    print('%s = %s' % ('.'.join([str(x) for x in oid]), not val.isValue and 'N/A' or val.prettyPrint()))
print('done')

print('Unloading MIB modules...'),
mibBuilder.unloadModules()
print('done')

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See also: library reference.