netdev - RE: Setting alternate MAC addresses on e1000

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Date:	Wed, 2 Apr 2008 10:41:55 -0700
From:	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>
To:	"Carsten Aulbert" <carsten.aulbert@....mpg.de>
Cc:	<netdev@...r.kernel.org>, <e1000-devel@...ts.sourceforge.net>
Subject: RE: Setting alternate MAC addresses on e1000

Carsten Aulbert wrote:
> Yes, with MAGIC=0x109a8086 I can set the MAC address of eth1.

good, I think you need to just use that way.

> The Intel specs state that word 37H is a pointer to an "alternate MAC
> address". My boss things it would be wise to let the original MAC
> address in place and just add another MAC address, so that we can
> easily revert to the old "official" one by writing 0xffff into that
> word. 

The alternate MAC address typically refers to a MAC used only for
management/ASF/IPMI traffic.  I don't think that is what you want.

According to our internal documents that I have access to, word 37h is
not what you think it is on 82573V/L.

PXE Words (words 30h thru 3Eh)
Words 30h through 3Eh have been reserved for configuration and version
values to be used by PXE code.

> Has anyone experience with that approach? In principle that should be
> easy, however, I don't know where/how to find 6 free bytes from the
> table given in Intel's docs.
> 
> Thanks again and hopefully someone has some light for my brain ;)

I think that you should stick with programming the original MAC address.
Start messing around with other words and you're bound to get yourself
into trouble.

Jesse
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