VLAN Trunc SNMP

Unanswered Question
Aug 10th, 2012
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  • Cisco Employee,

Hi there.




I'm trying to get the VLAN's a trunc port is a member of using snmp using the CISCO-VTP-MIB


The following key holds this information: .1.3.6.1.4.1.9.9.46.1.6.1.1.4

(.iso.org.dod.internet.private.enterprises.cisco.ciscoMgmt.ciscoVtpMIB.vtpMIBObjects.vlanTrunkPorts.vlanTrunkPortTable.vlanTrunkPortEntry.vlanTrunkPortVlansEnabled)

As far as i know the result is a hex value thet has to be transfered into a binary value, and then count the positions of the enabled bits to find out what vlans exists in a trunc.

If i query the snmp for a port i get the following result:

60 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 80 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00









Converting this to binary gives me:

0110000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000000000000000000000000111100000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000


if i count the enabled bit's position i get the following result;

1,2,200,201,202,203


The VLANS enabled in that trunk is only:

1,2,200


Why do i get readings about vlans not present?


If i remove VLAN 200 from the trunk the reading is correct


if i replace vlan 200 with vlan 201 the reading is correct.


The same applies to vlan 1024, if i add that vlan i get enabled bits on vlan 1024,1025,1026


Is there anyone who can point me in the right direction getting only the correct vlans listed when quiery SNMP v2

The switch i'm querying is a WS-C2960G-8TC-L


Regards

Alexander Eid

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haneid Fri, 08/10/2012 - 13:01
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  • Cisco Employee,

Problem solved


The hexto bin converter i was using (vb.net) was not converting correctly, solved by manually do the conversion


Thanks to all of you that looked into it



Regards

Alexander EId

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