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Subj:	Re: Ethernet configuration problem

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Date: 8 Aug 90 17:08:20 GMT
From: rogue.llnl.gov!oberman@lll-winken.llnl.gov
Organization: Lawrence Livermore National Laboratory
Subject: Re: Ethernet configuration problem
Message-Id: <1990Aug8.100820.1@rogue.llnl.gov>
References: <527096E30C9F8050D1@fccc.edu>
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In article <527096E30C9F8050D1@fccc.edu>, STODOLA@FCCC.EDU (Bob Stodola) writes:
> We have encountered an ethernet configuration problem that we cannot find in
> any of the books and our local (DEC) network specialist is unable to shed any
> light on.  If anyone has an answer, I would appreciate a direct reply as
> I am not on this list.
> 
> We have a DESPR (DIGITAL's thinwire repeater) attached to a DELNI which is
> attached to a thickwire coax (<300m) via an H4000 tranceiver.  Thinwire devices
> on the DESPR segment and thickwire devices on the DELNI can see the rest of the
> network, but not each other.  At first we thought this to be a communications
> problem between a Silicon Graphics and Sun TCP/IP, but then it happened again
> in another location with equipment from Western Digital, MIPS, Xyplex and DEC,
> so I guess there is something basically wrong with the configuration.  If any-
> one has the answer, I'd greatly appreciate it.

Bob, take a look at the documentation with the DESPR. You have a clearly
illegal configuration. And, while the documentation does not detail the symtoms
of the problem, you are describing them to a T.

802.3 states that a repeater must be connected to the network with a MAU with
SQE disabled. Well, an H4000 is not 802.3 complient in the first place. In the
second it always has the Ethernet V2 heartbeat (almost the same as SQE)
anabled. And that is propagated through the DELNI to all of the ports.

To fix the problem, replace the H4000 with an H4005 or some third party MAU
that is 802.3 and has SQE disabled. Or put the DESPR on its own MAU. The first
method will result in no SQE for every device on the DELNI which may cause a
lot of problems, so I prefer the second.

And, before I get a ton of mail, the DEREP in not 802.3 and should be connected
to an H4000. Never an H4005 or other 802.3 MAU. And, DEC says that direct
connection to the cable with an H4000 will work even though 802.3 prohibits it.
But DEC says (in the DESPR manual) that connection to a DELNI which is
connected to the cable with an H4000 won't work. There are other provisos for
DELNIs not connected to a cable.

					R. Kevin Oberman
					Lawrence Livermore National Laboratory
					Internet: oberman@icdc.llnl.gov
   					(415) 422-6955

Disclaimer: Don't take this too seriously. I just like to improve my typing
and probably don't really know anything useful about anything.