[AGENT++] usm counters - usmStatsNotInTimeWindows and usmStatsUnknownEngineIDs keeps incrementing by one after every snmpV3 get/set operation

[Frank Fock]

Hi,

The behaviour you observed is normal, the NET-SNMP process cannot remember
the engine ID and time between two runs. When you manually specify the 
engine ID of the agent++ agent, then the counters will not increment.

Best regards,
Frank



> On 25 Feb 2016, at 06:51, jc rani <ranisastra at gmail.com> wrote:
> 
> Hi
> 
> I ran agentpp example code cmd_ext_mib and performed snmp v3 get/set
> request operation and got snmp response successfully. But found that during
> every get/set operation, the counters -  usmStatsNotInTimeWindows and
> usmStatsUnknownEngineIDs got incremented everytime.
> 
> For instance:
> 
> Initially the counter values are usmStatsUnknownEngineIDs - 0 ;
> usmStatsUnknownEngineIDs - 0
> 
> After snmpwalk operation,
> $ snmpwalk -v3 -u MD5DES -l authPriv -a MD5 -A MD5DESUserAuthPassword -x
> DES -X MD5DESUserPrivPassword 20.0.0.162:12345 1.3.6.1.6.3.15.1.1
> SNMP-USER-BASED-SM-MIB::usmStatsUnsupportedSecLevels.0 = Counter32: 0
> *SNMP-USER-BASED-SM-MIB::usmStatsNotInTimeWindows.0 = Counter32: 1*
> SNMP-USER-BASED-SM-MIB::usmStatsUnknownUserNames.0 = Counter32: 0
> *SNMP-USER-BASED-SM-MIB::usmStatsUnknownEngineIDs.0 = Counter32: 1*
> SNMP-USER-BASED-SM-MIB::usmStatsWrongDigests.0 = Counter32: 0
> SNMP-USER-BASED-SM-MIB::usmStatsDecryptionErrors.0 = Counter32: 0
> 
> After another snmpwalk operation,
> $ snmpwalk -v3 -u MD5DES -l authPriv -a MD5 -A MD5DESUserAuthPassword -x
> DES -X MD5DESUserPrivPassword 20.0.0.162:12345 1.3.6.1.6.3.15.1.1
> SNMP-USER-BASED-SM-MIB::usmStatsUnsupportedSecLevels.0 = Counter32: 0
> *SNMP-USER-BASED-SM-MIB::usmStatsNotInTimeWindows.0 = Counter32: 2*
> SNMP-USER-BASED-SM-MIB::usmStatsUnknownUserNames.0 = Counter32: 0
> *SNMP-USER-BASED-SM-MIB::usmStatsUnknownEngineIDs.0 = Counter32: 2*
> SNMP-USER-BASED-SM-MIB::usmStatsWrongDigests.0 = Counter32: 0
> SNMP-USER-BASED-SM-MIB::usmStatsDecryptionErrors.0 = Counter32: 0
> 
> Performed a get operation on usmStatsUnknownEngineIDs
> $ snmpget -v3 -u MD5DES -l authPriv -a MD5 -A MD5DESUserAuthPassword -x DES
> -X MD5DESUserPrivPassword 20.0.0.162:12345 .1.3.6.1.6.3.15.1.1.4.0
> *SNMP-USER-BASED-SM-MIB::usmStatsUnknownEngineIDs.0 = Counter32: 3*
> 
> Performed a get operation on usmStatsWrongDigests
> $ snmpget -v3 -u MD5DES -l authPriv -a MD5 -A MD5DESUserAuthPassword -x DES
> -X MD5DESUserPrivPassword 20.0.0.162:12345 .1.3.6.1.6.3.15.1.1.5.0
> SNMP-USER-BASED-SM-MIB::usmStatsWrongDigests.0 = Counter32: 0
> 
> Now again performed a get operation on usmStatsUnknownEngineIDs
> $ snmpget -v3 -u MD5DES -l authPriv -a MD5 -A MD5DESUserAuthPassword -x DES
> -X MD5DESUserPrivPassword 20.0.0.162:12345 .1.3.6.1.6.3.15.1.1.4.0
> *SNMP-USER-BASED-SM-MIB::usmStatsUnknownEngineIDs.0 = Counter32: 5*
> 
> 
> So what I could infer is that after every get/set operation, the counters
> -  usmStatsNotInTimeWindows and usmStatsUnknownEngineIDs gets incremented
> by one.
> Could you please explain why the counters gets incremented after every
> get/set operation?
> 
> Thanks and Regards,
> Rani
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