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Date:      Fri, 4 Aug 2000 11:40:18 -0700 (PDT)
From:      "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net>
To:        oberman@es.net (Kevin Oberman)
Cc:        behanna@zbzoom.net, arap@oduurl.ru (Alexander), strbenjr@yahoo.com (Ben Hacker Jr), fug-washdc@Sytex.Net (list DC-FBSD), freebsd-questions@FreeBSD.ORG (questions FBSD), freebsd-stable@FreeBSD.ORG (Stable FBSD), bhacker1@csc.com (Ben Hacker Jr)
Subject:   Re: Router "ep2" issue
Message-ID:  <200008041840.LAA80077@gndrsh.dnsmgr.net>
In-Reply-To: <200008041542.e74FgsU32161@ptavv.es.net> from Kevin Oberman at "Aug 4, 2000 08:42:54 am"

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> >     Do these problems happen during thunderstorms, perchance?
> > 
> >     One of my coworkers recently turned me on to the fact that the
> > ethernet standard requires that the NICs, and all components of the
> > network, be properly grounded (no, not just to the box chassis) to be
> > reliable.  Of course, no one really does this, and most of the time
> > you can get away without it, but sometimes you can't.
> 
> Could provide a citation for this. I can't find this anywhere in my
> copy of 802.3. Of course, it's a rather thick document and I could
> have missed something, but grounding is something that Ethernet was
> deliberately designed to NOT require.

I don't think you'll find this in 802.3, but perhaps in TIA-565
or TIA-606.  The unused pairs in CAT-5 cables should be AC grounded
to telco/chassis ground to minimize crosstalk, RFI/EMI and EMP reception/
transmission.  If you look on most NIC cards you'll see that the
unused pairs are hook through 47pF (or there about) to ground.

> The spec does call for medium grounding for 10Base5 and allows for it
> (but does not require it) for 10Base2, but that's about it.

Anyone running Coax of any real length is a fool not to have it
properly gounded.  Without the ground it is one big antenna, and
in a lightning storm the EMP wave can induce 100's to 1000's of
volts on a long piece of ungrounded coax, especially something
as large as 10Base5.


-- 
Rod Grimes - KD7CAX @ CN85sl - (RWG25)               rgrimes@gndrsh.dnsmgr.net


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