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Date:      Mon, 8 Jan 2001 08:57:56 -0600
From:      "Jason Smethers" <jsmethers@pdq.net>
To:        "Nicole" <nicole@unixgirl.com>
Cc:        <freebsd-net@FreeBSD.ORG>
Subject:   Re: Problem with fxp0 card and slowing/dying transmits - now I'm really confused
Message-ID:  <00ce01c07983$630ac220$edcf1f40@pdq.net>
References:  <XFMail.010108015255.nicole@unixgirl.com>

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From: "Nicole" <nicole@unixgirl.com>
>  Also one other weird question. What is the real difference between
a cable
> with 2 pairs and a cable with 4 pairs were 10/100 ethernet is
concerned. On
> another server that was using a SMC/DEC card I found it would go
nuts when it
> had a 2 pair cable, but worked Ok with a 4 pair cable. From
everything I can
> tell, 10/100 ethernet should not care abt the extra 2 pairs.
>
>  Nicole
>    off to a padded room

You'd think that just because the extra pairs aren't used to transmit,
wouldn't you. It is probably a good guess that that two pair cables
have all four pairs in it but the extra two are not connected? In this
case the extra two pairs are not grounded and thus act as antennae. It
doesn't take a lot of interference induce errors on a 100Mbp/s
Ethernet system.

Since you did not explicitly say that you tried multiple two and four
pair cables, etc...

Other problems may include cheap materials or incorrect RJ-45
connectors. e.g. the cable is solid conductor and the RJ-45 connector
is designed for stranded conductor wire. There may be bends in the
cable, an excessive amount of untwisting of the pairs at termination
points, or the wire may be patched through to many patch panels. Are
you sure that it is category 5 cable? Is or was the network punch
panels once used to connect telephones? If it was there may be bridge
taps laying around.

- Jason



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