Stupid Mac Ethernet question

Richard A. Cini rcini at
Sun Jan 15 13:21:50 CST 2006

Talking about color coding, I do something similar with my structured
wiring. In-wall is blue, green or gray depending on grade (5e, 5, and
telephone, respectively). From the router to the firewall is red. The
firewall to the switch is green. Workstations use yellow patch cables.
Servers use blue. Black is a temporary connection. 

-----Original Message-----
From: cctalk-bounces at [mailto:cctalk-bounces at]
On Behalf Of Pete Turnbull
Sent: Sunday, January 15, 2006 1:11 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Stupid Mac Ethernet question

On Jan 14 2006, 18:10, Richard A. Cini wrote:

>             I just recently upgraded the network cabling in my house
to 5e
> as part of some new construction, and I also upgraded the networking
> components. Now, all of my normal machines run at 100 full duplex.

>             The strangest thing happened to my Mac IIci - the
> connection no longer works. I don't even get a link light on the new
> (a Cisco/Linksys switch). However, when I plug the Mac into a plain
old 10BT
> hub and then uplink it to the switch, I at least get a link light.

> Does this problem resonate with anyone?

Yes, it does.  Check that the cable that came with the Mac is a
straight-through Ethernet Cat 5 cable, not a crossover (pins 1+2 at one
connected to pins 3+6 at the other; ie the orange and green pairs).

It could also be an autonegotiation (speed/duplex) problem, but I'd
check the cable anyway, becasue that's usually easy to do by eye.

Sometimes Macs have been supplied with crossover cables which work fine
on devices that have ports which autodetect crossover -- some hubs and
switches do this to make interconnections easier.

I once was on the receiving end of a rant from a visitor who had a
crossover cable, though neither of us realised it immediately.  I
tested the socket, which was live and my Fluke OneTouch got a link and
a DHCP lease.  I connected it to his Mac; that showed a link.  I tested
his cable, which showed as a crossover.  I told him that was the
problem.  Not withstanding the "Wiremap Error" displayed on the
OneTouch, he insisted it was our network at fault, and "of course" his
cable was the right type "because it works at home".  I gave him a
brand-new patch cable sealed in a polythene bag and left him to get
over it.

BTW, there is no colour code convention for patch cables, but we like
to use a local system that helps to prevent most accidents and
puzzlements: grey is temporary, purple is crossover, black is serial,
and pink ("barbie-net") is telephony.  Anything else is "Just
Ethernet".  It might be wise to adopt some similar convention, at least
to distinguish crossover cables.

Pete						Peter Turnbull
						Network Manager
						University of York

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