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From: alan@COLUMBIA.EDU.UUCP
Newsgroups: mod.protocols
Subject: Submission for mod-protocols
Message-ID: <8702232242.AA02551@columbia.edu>
Date: Mon, 23-Feb-87 17:42:29 EST
Article-I.D.: columbia.8702232242.AA02551
Posted: Mon Feb 23 17:42:29 1987
Date-Received: Thu, 26-Feb-87 21:32:48 EST
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Path: columbia!alan
From: alan@columbia.UUCP (Alan Crosswell)
Newsgroups: mod.protocols,mod.computers.vax
Subject: Need help with LAN Bridges
Message-ID: <4373@columbia.UUCP>
Date: 23 Feb 87 22:42:25 GMT
Reply-To: alan@columbia.edu (Alan Crosswell)
Organization: Columbia University CS Department
Lines: 34


We have several LAN Bridges interconnecting departmental ethernets
to our campus "backbone."  We have recently noticed that a lot of
traffic that should be filtered by the LAN Bridge is not being filtered;
packets between a host on the backbone and another department are showing
up on a second department's network.  These are not broadcasts,  they
are things like tcp/telnet and tcp/ftp.

Unfortunately,  we do not have a VMS system or RBMS so I can't dump
out the LAN Bridge's tables to see if that will provide any clueas
to what it going on.  My understanding was that the factory default
would be to do all the right filtering so we wouldn't need RBMS for
day-to-day stuff -- only for unusual situations.....

I have also noticed the LAN Bridge for our department is transmitting
a "LAN Bridge protocol" packet about once a second onto the departmental
network.

The LAN Bridge installation manual (the only documentation of the thing
I have) says that the Bridges talk to each other when they boot so that
they can see if there are any loops.  Are they saying anything else to
each other and can they possibly get confused if, for instance, some of
them have the "A" port plugged into the backbone while others are plugged
in with the "B" port?

Any help and/or explanations of how LAN Bridges work or what might be
wrong would be greatly appreciated!  One of our departmental networks
that just got connected to the backbone may have to disconnect -- the
extra noise is wiping out their diskless SUN performance.

Alan Crosswell
Columbia University
alan@columbia.edu
(212) 280-3754