Re: Catalyst 2950: dot1dTpFdbAddress (.1.3.6.1.2.1.17.4.3.1.1) i

zvivered1 · ‎10-23-2011

Hello,

According to Document 40367 I'm trying to get the MAC address connected to a specified port.

The first stage was:

snmpwalk 192.168.0.254 -Os -c public -v 2c .1.3.6.1.2.1.17.4.3.1.1

But the response was:

mib-2.17.4.3.1.1 = No Such Instance currently exists at this OID

The switch details are:

Switch#show version

Cisco Internetwork Operating System Software

IOS (tm) C2950 Software (C2950-I6Q4L2-M), Version 12.1(22)EA4, RELEASE SOFTWARE (fc1)

Compiled Wed 23-Mar-05 15:33 by yenanh
Image text-base: 0x80010000, data-base: 0x80562000
ROM: Bootstrap program is C2950 boot loader

Switch uptime is 17 hours, 52 minutes
System returned to ROM by power-on
System image file is "flash:/c2950-i6q4l2-mz.121-22.EA4.bin"

cisco WS-C2950G-24-EI (RC32300) processor (revision L0) with 21039K bytes of memory.

Processor board ID FOC0931Z7VL
Last reset from system-reset
Running Enhanced Image

24 FastEthernet/IEEE 802.3 interface(s)

2 Gigabit Ethernet/IEEE 802.3 interface(s)

32K bytes of flash-simulated non-volatile configuration memory.
Base ethernet MAC Address: 00:14:A9:E0:3C:80
Motherboard assembly number: 73-7280-05
Power supply part number: 34-0965-01
Motherboard serial number: FOC09312RKC
Power supply serial number: DAB0924BFK2
Model revision number: L0
Motherboard revision number: A0
Model number: WS-C2950G-24-EI
System serial number: FOC0931Z7VL
Configuration register is 0xF

SNMP is enabled in this switch:

Switch#show snmp
Chassis: FOC0931Z7VL
25161 SNMP packets input
0 Bad SNMP version errors
0 Unknown community name
0 Illegal operation for community name supplied
0 Encoding errors
25146 Number of requested variables
0 Number of altered variables
13 Get-request PDUs
25139 Get-next PDUs
0 Set-request PDUs
25161 SNMP packets output
0 Too big errors (Maximum packet size 1500)
6 No such name errors
0 Bad values errors
0 General errors
25152 Response PDUs
0 Trap PDUs
SNMP global trap: disabled
SNMP logging: disabled
SNMP agent enabled

What is the reason the OID is not responding ?

Thanks,
Zvika.

Martin Ermel · ‎10-24-2011

you used public as your community string but you didn't used community string indexing as mentioned in the doc (http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a00801576ff.shtml); e.g. public@1 for vlan 1

to get the mac address correlated to a port and you know the Vlan ID of the port, it is as follows:

get the ifIndex of the interface by quering the IfName [.1.3.6.1.2.1.31.1.1.1.1]

get the bridge port to ifIndex mapping by quering dot1dBasePortIfIndex [.1.3.6.1.2.1.17.1.4.1.2] > with snmp community string indexing

lookup the bridge port in the forwarding table by quering dot1dTpFdbPort [.1.3.6.1.2.1.17.4.3.1.2] > with snmp community string indexing

lookup the instance of the matching entry from the forwarding table by quering dot1dTpFdbAddress [.1.3.6.1.2.1.17.4.3.1.1] > with snmp community string indexing

>>> this is the MAC Address

MAC addresses are hold in a seperate table for each vlan; the information is stored in the forwarding table [dot1dTpFdbAddress (.1.3.6.1.2.1.17.4.3.1.1) ]. The question is now, how to retrieve this information for each vlan (i.e. you have one OID but multiple vlans)? - The solution is snmp community string indexing - you have to add the @ character along with the vlanID to the community string. If the RO communtiy string is snmpRO you have to use e.g snmpRO@10 to get the information for vlan 10.

if you do not know the VLAN Id of the port you first have to query all activ Vlans to find the bridge port, for details read this doc:

http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a00801c9199.shtml

and

http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094a9b.shtml

Catalyst 2950: dot1dTpFdbAddress (.1.3.6.1.2.1.17.4.3.1.1) is not responding