From owner-freebsd-questions Mon Aug 7 08:07:12 1995 Return-Path: questions-owner Received: (from majordom@localhost) by freefall.cdrom.com (8.6.11/8.6.6) id IAA08606 for questions-outgoing; Mon, 7 Aug 1995 08:07:12 -0700 Received: from elf.kendall.mdcc.edu (elf.kendall.mdcc.edu [147.70.150.122]) by freefall.cdrom.com (8.6.11/8.6.6) with ESMTP id IAA08551 for ; Mon, 7 Aug 1995 08:06:59 -0700 Received: (from freelist@localhost) by elf.kendall.mdcc.edu (8.6.11/8.6.9) id KAA24119; Mon, 7 Aug 1995 10:58:40 -0400 Date: Mon, 7 Aug 1995 10:58:39 -0400 (EDT) From: "Don's FList drop" To: rhh@ct.picker.com cc: questions@freefall.cdrom.com Subject: Re: (?) RJ45 Crossover Cable Question (Pin numbering) In-Reply-To: <9508062304.AA22800@elmer.ct.picker.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: questions-owner@FreeBSD.org Precedence: bulk You can look in the FAQ for comp.dcom.lans.ethernet, but I bet this has all the answers you need... On Sun, 6 Aug 1995, Randall Hopper wrote: > In short, does someone know the convention for numbering the pins on an > RJ45 cable connector? If the cable w/ attached connector is held in front of > you, pins on the near side of the connector and pointing up (cable attached to > the bottom), are the pins 1-to-8 numbered ascendingly from left-to-right or > right-to-left? Liberated from: Linux Ethernet-HOWTO-5.html#ss5.2 5 CABLES, COAX, TWISTED PAIR 5.2 Twisted Pair If you are only connecting two machines, it is possible to avoid using a hub, by swapping the Rx and Tx pairs (1-2 and 3-6). If you hold the RJ-45 connector facing you (as if you were going to plug it into your mouth) with the lock tab on the top, then the pins are numbered 1 to 8 from left to right. The pin usage is as follows: Pin Number Assignment ---------- ---------- 1 Output Data (+) 2 Output Data (-) 3 Input Data (+) 4 Reserved for Telephone use 5 Reserved for Telephone use 6 Input Data (-) 7 Reserved for Telephone use 8 Reserved for Telephone use Some cards, like the wd8013 can sense reversed polarity, and will adjust accordingly. Also note that 3 and 6 must be a twisted pair. If you make 3-4 a twisted pair, and 5-6 the other twisted pair, your cable may work for lengths less than a metre, but will fail miserably for longer lengths.