[mrtg] 3com MAC address Tracking

James Amann jamann at gsu.edu
Fri Nov 16 21:48:13 MET 2001


I am trying to write a script that will query 3com switches (ssII 1100, 1000, 3300, 3000 and desktop 1000) and return the MAC addresses learned by each port along with the applicable port number.

I found the tidbit below from an old post which gives the OID for the MAC as well as the MAC to port mapping.  The OIDs do in fact return the info I need, BUT (arrg) they table only seems to return approx 30 mappings.

Example, If I telnet to the switch and check its MAC database I might find 100 entries on a 24 port device.  The bulk of which are llearned by the downlink port.  When I walk the MIB I only see <30 most of which are from the downlink.  I cannot find any information in RFC1493 stating that the Dot1dTpFdbTable is limited to 30 entries, but it appears to be that way.  This makes no sense.  

Has anyone dealt with, worked on, or possibly tamed this beast already?  Any help would be greatly appreciated.  Thanks.

To elaborate just a bit, what you are looking for is in the Dot1dTpFdbTable
(  This is where each MAC address known by the switch
is stored along with the port on which it is located along with the "state"
like learned, static, self, etc.  You will need a device that supports RFC
1493 and you may need the mibs in RFC 1493 if you want to look at them in
GetIf.  Let me know if you need more detail.


James McGovern Amann
Network Technician Lead
Georgia State University
UCCS / Network Planning 
PH: 404.651.1574
FX: 404.651.4669
PG: 404.476.7754
jamann at gsu.edu

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