Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!think!ames!ncar!boulder!gore!jacob
From: jacob@gore.com (Jacob Gore)
Newsgroups: comp.sys.next
Subject: Re: Connecting a NeXT to twisted-pair
Message-ID: <130051@gore.com>
Date: 14 Dec 89 05:00:11 GMT
References: <341@egg-idINEL.GOV>
Reply-To: jacob@gore.com (Jacob Gore)
Organization: Gore Enterprises
Lines: 65

In article <341@egg-idINEL.GOV> rhp@INEL.GOV (Robert Powell) writes:
>It is a problem because our building is only wired with twisted-pair thick-net
>ethernet.  Our networking people tell me that I need a thick-net to thin-net
>bridge or repeater, at a cost of around $2,600!  Has anyone else out there

/ comp.sys.next / izumi@violet.berkeley.edu (Izumi Ohzawa) / Dec 13, 1989 /
> ... I noticed several articles back about a router/bridge
> made out of a cheap PC XT clone + 2 Western Digital Ethernet cards
> for under $800-900.  If this box can have 1 twisted-pair Ethernet
> card and another thin-Ethernet card, it should do the job.
>
>Whoever posted that article, would you clarify this point?

OK, here it is.  It certainly can be done, but it's probably not the best
way to do it.

Your best bet is calling the supplier (or manufacturer) of your TP hub and
asking them if they have a TP to Thinnet converter.  I'm told that
Cabletron has one for their TP for about $500 (I don't know if that is
educational or "normal" price).

Also, I know HP sells (or at least it did last year) an adapter that hooks
in between a drop cable from a transceiver on one side and a Thinnet outlet
on the other.  Sorry, I don't have the part number or the price.  You would
still need a TP transceiver between the TP wire and the drop cable.

If you do want to use a PC for this, here are the considerations:

The way things are done now, you pretty much need to buy your TP
transceiver and the TP hub from the same manufacturer.  So, if you do buy a
TP Ethernet card from Western Digital, you have to make sure that it is
compatible compatible with your hub (i.e., ask them before you buy).

In the likely event that it's NOT compatible with your hub, you can simply
buy the standard card (WD8003E, a.k.a. "EtherCard Plus", I believe) and use
the TP transceiver from your hub's vendor and a drop cable to connect to
the Thicknet port on the card.  The card also has a Thinnet port, so you
can just buy two WD8003E.  (No, you can't get by with just one card, you
need one for each network.)

Unless you really want to have a separate IP subnet on your side of the PC,
instead of PCroute you should use its sibling, PCbridge.  It is available
from the same places (definitely accuvax.nwu.edu and probably
uunet.uu.net).  It is simpler to set up (no configuration required), and
you won't end up having to assign an IP subnet just for one NeXT -- it will
be on the same IP subnet as all the other hosts on that TP network.

For PCbridge you may want a faster PC than for PCroute, because unlike a
router, a bridge forwards every single packet it gets.  Packet forwarding
in PCroute/PCbridge is several times slower than packet filtering.

By the way, I should mention that you do NOT need a monitor card or a
monitor, as long as the boot PROMs of the PC clone you buy do not insist on
checking for one (most don't).

So, here are the details about how you can use a PC between networks (not
the only way to do it, there is other software too).  I personally would
opt for a TP to Thinnet adapter from the TP vendor if it was available, and
if not, I'd go for a single-port receiver from Cabletron (not the only
source, but my personal favorite).  A PC clone just seems like a rather
bulky transceiver...

Jacob
--
Jacob Gore		Jacob@Gore.Com			boulder!gore!jacob