Path: utzoo!utgpu!watmath!clyde!mcdchg!chinet!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!amdcad!sun!pitstop!sundc!seismo!uunet!mcvax!enea!kth!draken!chalmers!ae.chalmers.se!goeran
From: goeran@ae.chalmers.se (Goran Bengtson)
Newsgroups: comp.dcom.lans
Subject: Re: DEC LAN Bridges
Message-ID: <78@ae.chalmers.se>
Date: 26 Oct 88 21:58:11 GMT
References: <773@dogie.edu> <1041@gvgpsa.GVG.TEK.COM> <23652@pprg.unm.edu>
Organization: Dept. of Applied Electronics. Chalmers Univ. of Technology.
Lines: 39

In article <23652@pprg.unm.edu>, cyrus@pprg.unm.edu (Tait Cyrus) writes:

> Ok, so far nothing "really" out of the ordinary.  Well, it turns out
> that both "boxes" are IBM PC/RT's, one running AIX and the other having
> BSD 4.3 installed on it.  I am NOT saying that the IBM PC/RT (with UB
> ethernet boards) is causing the problems, it is that I find it fairly
> interesting that there is such a coincidence.
> 
> While watching the net, I have walked up to an IBM PC/RT and powered
> it off allowing it to reboot; no bogus packets seen.  I have shut the
> IBM down (gracefully); again no bugus packets.
> 
> Has anyone seeing these bogus packets noticed similar circumstances?
> Could it the IBM PC/RT?  Could it the UB ethernet board?  Could I be
> looking at events that are pure coincidence?  Am I full of it? :-) 

PC/RT with UB boards (at least some models) IS a source.  We have
confirmed that. 

The UB board sends a packet from it's internal memory when initilized
and/or started.  Warm restart may give packet with ANY content 
(usually part of the last packet seen before shutdown) so you can get
ANY source address in that packet. Cold restart usually gives 1's or
0's (dynamic ram...).

We think that it IS possible to initialize the board without causing
this problem.  We have not seen it from PC/RT running AIX,  only from
PC/RT's running Bsd 4.3 (with or without Andrew File system).
ifconfig down/up cause a random packet to be sent! 

Our temporary fix was to make sure that a KNOWN packet (short,  but with
legal source and destination address) is transmitted when the board is
initiated.
-- 
Goran Bengtson				Email:	goeran@ae.chalmers.se
Dept. of Applied Electronics
Chalmers Univ. of Technology		Phone:  +46 31 721825	(int)
S-412 96 Gothenburg				031 721825	(nat)
Sweden