2924XL SNMP MAC Table Read Oddity

Feb 23, 2008 6 Replies

Can anyone help with this, it's got me puzzled as to why I can't obtain the MAC table via SNMP from my 2924XL switches...



IOS (tm) C2900XL Software (C2900XL-C3H2S-M), Version 12.0(5)WC17, RELEASE SOFTWARE (fc1)



From the Telnet session:



loft-sw01#show mac
> Dynamic Address Count: 12
> Secure Address Count: 0
> Static Address (User-defined) Count: 0
> System Self Address Count: 49
> Total MAC addresses: 61
> Maximum MAC addresses: 2048
> Non-static Address Table:
> Destination Address Address Type VLAN Destination Port
>

looks like you got the static MAC's and the dynamic MACS for VLAN 1

see Cisco doc "How To Get Dynamic CAM Entries (CAM Table) for Catalyst Switches"

formatting link
to get each dynamic CAN entry - you need to retriev one VLAN at a time using

a modifued community string in that you append "@" at the end of the community string

You're a star :) works a treat, thanks alot

One more question...

This is all for part of my uni project, network monitoring/MAC tracking system - would you recommend using SNMP to obtain the MAC table & interface and then match them up, or zip in over telnet and get it using the "show mac-address-table" command and then parse the output. I know it both gets me the same information but which is going to be the faster.

not sure as I have never tried doing this type of comparison.

if you have time do both for the learning experience

I have not a clue - however:-

The SNMP will involve a 'transaction' for each VLAN the telnet method is a single command for all VLAN

Against that it is possible that setting up the telnet session may have more overhead - particularly if fancy authentication is used.

Have you considered rcommand.http? Just to add confusion:-)

haven't got a clue what that is...

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