Path: utzoo!attcan!uunet!ginosko!gem.mps.ohio-state.edu!apple!csibtfr!excelan!edc
From: edc@excelan.com (Eric Christensen)
Newsgroups: comp.dcom.lans
Subject: Re: Ethernet max length problems
Keywords: repeaters? ethernet too long
Message-ID: <451@excelan.COM>
Date: 22 Sep 89 14:52:25 GMT
References: <634@elan.elan.com>
Sender: news@excelan.COM
Reply-To: edc@ka.UUCP (Eric Christensen)
Organization: Excelan, Inc., San Jose, Califonia
Lines: 38

In article <634@elan.elan.com> jlo@elan.com (Jeff Lo) writes:
>We have a problem.  We currently have a single thin ethernet running through
>our office, with a mix of Unix and DOS machines connected to it.  All of
>the Unix machines use IP to talk to each other, and the DOS machines are
>using something called Network-OS which uses something (?) other than IP.
>The problem is that we are hitting the maximum length restriction of the
>thin ethernet and some of the PC's are experiencing difficulties,
>presumably because their ethernet boards are having problems with the
>too-long cable.  Since the DOS machines don't speak IP, we cannot simply
>split the ethernet into two separate networks with an IP router in between.
>So, what I am looking for is something I put on the line, a repeater or
>something, if such a thing exists for ethernet, to allow us to seemingly
>have one long (>185m) ethernet.  Thanks!

Ethernet repeater are available form a number of vendor. BICC and Cabletron 
both make excellent units.

If traffic levels are high on your net, a bridge may be a better solution.
Since a bridge forwards packets at the MAC layer, it's protocol independent
and has the advantage of keeping packets between nodes on one side of the 
repeater off the net on the other side. They're generally a little bit more
expensive than a repeater, but are much more useful aas the network grows
larger. Again, there are may manufacturers of ethernet bridges, but I've
had real good experiance with Retix, NAT, and Cabletron.

One warning when choosing a bridge. Pick a vendor and stick with them. There
are incompatibilities in the implementation of the spanning tree protocol that
the bridges use to talk to each other. While this doesn't usually cause too
much trouble (unless your actually building a spanning tree net topology), I
have seen one bridge tell another (from a different vendor) to not forward
packets one of its interfaces. This can be a problem if your boss is on the 
segment that keeps getting shut down! :-)


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| Eric Christensen  -  Sr. System Administrator  -  Excelan, A Novell Company |
| Email: edc@excelan.COM        {ames | apple | mtxinu | leadsv }!excelan!edc |
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