Network topology [Solved]

Dale W. Carder dwcarder at
Thu Oct 16 02:18:44 UTC 2008

On Oct 15, 2008, at 1:35 PM, Colin Alston wrote:

> On 2008/10/15 06:29 PM Colin Alston wrote:
>> Is there any kind of cunning trick to detect standard layer2  
>> switches along a path without stuff like STP?
> Apparently there isn't. Lots of people mentioned other tools, the  
> problem there is they have one thing in common which is polling  
> SNMP. I think it scales badly in general.

What is your reasoning behind this claim?  I would claim
quite the opposite compared to CLI or TL1.

> Maybe there should be something (I mean like, someone should come  
> up with a standard :P) to trace switches in a path

I've written a cruddy script that given a seed bridge, scrapes
L2 information obtained via CDP (I guess it could do LLDP, too)
and does a breadth-first search through a network.  Then I just
dump that into gnuplot format.  Getting the data is easy compared
to visualization.

A coworker of mine has written script to ask Rapid-STP speaking
switches about their current topology and builds a graph again
in gnuplot format.

A more challenging approach would be to scrape the mac forwarding
tables and stitch things together.  This would have to be done
per-vlan.  I think this approach (or similar) might be done by
Openview's L2 featureset.


Dale W. Carder - Network Engineer
University of Wisconsin / WiscNet

More information about the NANOG mailing list