pysnmp error on specific query

Question

I have been trying to implement code that loads my device MIBS and walks through all the OIDS. In this one case when I try to load the OID for snmp 1.3.6.1.2.1.11 smi throws an exception when trying to load a specific OID. The previous OID works successfully: '.1.3.6.1.2.1.11.29.0' but this one generates the error message '.1.3.6.1.2.1.11.30.0'

The exception is:

File "/opt/anaconda/lib/python2.7/site-packages/pysnmp/smi/rfc1902.py", line 859, in resolveWithMib raise SmiError('MIB object %r having type %r failed to cast value %r: %s' % (self.args[0].prettyPrint(), self.__args[0].getMibNode().getSyntax().__class.name, self.__args[1], sys.exc_info()[1])) ;SmiError: MIB object 'SNMPv2-MIB::snmpEnableAuthenTraps.0' having type 'Integer32' failed to cast value Integer32(808466736): ConstraintsIntersection(ConstraintsIntersection(ConstraintsIntersection(), ValueRangeConstraint(-2147483648, 2147483647)), SingleValueConstraint(1, 2)) failed at: "SingleValueConstraint(1, 2) failed at: "808466736"" at Integer32

Here is sample code that demonstrates the error. You will need to modify the DEVICE_IP. It is assuming that you are running SNMP v1 and against community 'public. It is running pysnmp version 4.3.2

from pysnmp.entity.rfc3413.oneliner import cmdgen
from pysnmp.smi.rfc1902 import ObjectIdentity

DEVICE_IP = 'localhost'


def get_oid(oid):
    """
    Requires a valid oid as input and retrieves the given OID
    """ 
    snmp_target = (DEVICE_IP, 161)
    cmdGen = cmdgen.CommandGenerator()
    result = None

    errorIndication, errorStatus, errorIndex, varBindTable =            cmdGen.nextCmd(
        cmdgen.CommunityData('public', mpModel=0),
        cmdgen.UdpTransportTarget(snmp_target),
        ObjectIdentity(oid, last=True),
        lexicographicMode=False
        )

    if errorIndication:
        print(errorIndication)
    else:
        for varBindTableRow in varBindTable:
            for name, val in varBindTableRow:
                try:
                    result = str(val)
                except:
                    raise
    return result

# Does not Throw Error
print get_oid('.1.3.6.1.2.1.11.29.0')

# Throws Error
print get_oid('.1.3.6.1.2.1.11.30.0')

Ilya Etingof Ilya Etingof · Accepted Answer · 2016-08-13T22:45:23

Your SNMP agent responded with 1.3.6.1.2.1.11.30.0=808466736 while OID 1.3.6.1.2.1.11.30.0 identifies MIB object snmpEnableAuthenTraps of type INTEGER with only two values permitted: 1 and 2.

Here is formal definition from SNMPv2-MIB:

snmpEnableAuthenTraps OBJECT-TYPE
    SYNTAX      INTEGER { enabled(1), disabled(2) }
    ...

So this time pysnmp seems to do the right thing - it shields you from the value that makes no sense. Root cause of this problem is the SNMP agent that sends malformed values for MIB objects.

pysnmp error on specific query

1 Answers