Re: Question about ethernet addresses

In article <gbrt7j0ik8@xxxxxxxxxxxxxxxxx>, J.J. O'Shea
<try.not.to@xxxxxxxxxxx> wrote:

On Mon, 29 Sep 2008 20:33:25 -0400, Frank J Warner wrote
(in article <290920081733251453%warnerf@xxxxxxxxxxxxxxxxxxxxxx>):

Hoping one of you sharp IT guys can answer a question about ethernet
addresses on my Mac. So far, I seem to be coming up with two different
addresses for a single machine, and I wonder which one is lying to me.

Running System Profiler yields the following for my G5's MAC address
under ethernet settings:
00:18:24:2a:b3:f4

Opening the Network pane of my System Preferences gives me a completely
different ethernet address:
00:0a:93:45:b1:14

(The two examples above have been munged in case hackers find these
addresses useful, but the differences are more or less as written.)

My understanding is that the ethernet address is a unique identifier
for my network card. If that's the case, why are two different system
tools reporting two different addresses, and which one is accurate?

You have two different MAC addresses, possibly one Ethernet and one wireless,
or you have two Ethernet cards. You should note that if your Bluetooth system
is set up as a PAN (Personal Area Network) which is common if you have some
Bluetooth-enabled cell phones (I have a Motorola RAZR) there will also be a
MAC address associated with Bluetooth, if you have properly configured the
phone. Where does System Profiler say your MAC address is, en0, en1, or en2?
Where does System Preferences/Network say your MAC address is, Ethernet,
Ethernet 1, Ethernet 2, AirPort, or Bluetooth PAN?

Yes, I'm on a wireless network at home. I do not have Bluetooth enabled.

Going deeper into System Profiler reveals that the first address is
associated with AirPort, en1, the second address with built-in
Ethernet, en0. (Built-in FireWire reports the same address as en0 but
with two additional hex digits.)

Is the second address the identifier for my network card?

-Frank

--
Here's some of my work:
http://www.franksknives.com
.

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