From owner-freebsd-questions Fri Aug 4 13: 4:42 2000 Delivered-To: freebsd-questions@freebsd.org Received: from whizzo.transsys.com (whizzo.TransSys.COM [144.202.42.10]) by hub.freebsd.org (Postfix) with ESMTP id 1200E37BA73 for ; Fri, 4 Aug 2000 13:04:39 -0700 (PDT) (envelope-from louie@whizzo.transsys.com) Received: from whizzo.transsys.com (localhost.transsys.com [127.0.0.1]) by whizzo.transsys.com (8.9.3/8.9.1) with ESMTP id QAA85387; Fri, 4 Aug 2000 16:04:31 -0400 (EDT) (envelope-from louie@whizzo.transsys.com) Message-Id: <200008042004.QAA85387@whizzo.transsys.com> X-Mailer: exmh version 2.1.1 10/15/1999 To: "Rodney W. Grimes" Cc: freebsd-questions@FreeBSD.ORG (questions FBSD) X-Image-URL: http://www.transsys.com/louie/images/louie-mail.jpg From: "Louis A. Mamakos" Subject: Re: Router "ep2" issue References: <200008041840.LAA80077@gndrsh.dnsmgr.net> In-reply-to: Your message of "Fri, 04 Aug 2000 11:40:18 PDT." <200008041840.LAA80077@gndrsh.dnsmgr.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Fri, 04 Aug 2000 16:04:31 -0400 Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG [Note trimmed To: and Cc: to freebsd-questions] > > > 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. I observed this first-hand years ago when 10Base-5 ("Thick" ethernet to you, buddy!) was run between two building, and underground at that. A lightning strike nearby caused the premature death of a bunch of thick ethernet transceivers, most convieniently located in the ceiling above various offices. There was also a considerable DC offset in the ground between the buildings, on the order of a couple of volts! I don't know if anyone ever measured the current when the cable was connected to the bulding ground in each building. I think this is why you're only supposed to ground the ethernet shield conductor in exactly one place. louie To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message