Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!killer!texbell!bellcore!jupiter!karn
From: karn@jupiter..bellcore.com (Phil R. Karn)
Newsgroups: comp.dcom.lans
Subject: Re: Some nodes can't reach others - is this a LanBridge problem?
Message-ID: <13818@bellcore.bellcore.com>
Date: 3 Feb 89 02:00:02 GMT
References: <17850@vax5.CIT.CORNELL.EDU>
Sender: news@bellcore.bellcore.com
Reply-To: karn@thumper.bellcore.com (Phil R. Karn)
Distribution: comp
Organization: Bell Communications Research, Inc
Lines: 20


Assuming that the hosts, interfaces, software and cables are all in good
shape, yes, it's possible for the LAN Bridge to be at fault.

In particular, the existing Lan Bridge firmware has a nasty bug that can
cause it to "learn" the broadcast address if someone erroneously uses it
in the source field of a packet. (I've seen this happen on a PC when
an improperly seated board worked well enough to generate packets, but
the address PROM read out as all 1's).

When a bridge learns the broadcast address, it will refuse to pass
broadcasts. This breaks ARP.  We had this problem occasionally on our
(rather large) bridged network until DEC finally sent us a new batch of ROMs
that fixed the problem.

By the way, my "locate" program began life one day when I was desperately
trying to locate the $#@!! station using the broadcast address as its source
address...

Phil