Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!rutgers!bellcore!ka9q.bellcore.com!karn
From: karn@ka9q.bellcore.com (Phil Karn)
Newsgroups: comp.dcom.lans
Subject: Re: Problems finding forwarding tables on LAN Bridges
Keywords: bridge
Message-ID: <13701@bellcore.bellcore.com>
Date: 29 Jan 89 00:05:37 GMT
References: <917@cernvax.UUCP>
Sender: news@bellcore.bellcore.com
Reply-To: karn@ka9q.bellcore.com (Phil Karn)
Organization: Secular Humanists for No-Code
Lines: 16


Yes, I've already done this here at Bellcore. I wrote a program called
"locate" that, given an ethernet address, reads a topology file and queries
the Lan Bridge 100s to find the segment containing that address.

The algorithm works by a simple process of elimination. You start with a
complete list of your cable segments, and you search each bridge's
forwarding table in turn for the target address. (I do this in parallel,
since the RBMS protocols are rather slow.) When a bridge replies that the
desired address is on port A, you can rule out the segment attached to port
B.  Eventually you (hopefully) end up with one segment.

The process is not 100% reliable, but it works well enough to be useful.  I
guess I'll ask about getting it released.

Phil