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Date:      Fri, 14 May 1999 17:25:10 +0200 (MET DST)
From:      Luigi Rizzo <luigi@labinfo.iet.unipi.it>
To:        nate@mt.sri.com (Nate Williams)
Cc:        Steve.Gailey@db.com, freebsd-hackers@FreeBSD.ORG
Subject:   Re: ifconfig: changing mac address
Message-ID:  <199905141525.RAA24858@labinfo.iet.unipi.it>
In-Reply-To: <199905141710.LAA11648@mt.sri.com> from "Nate Williams" at May 14, 99 11:10:38 am

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> > Is it possible to change the mac address of an ethernet card using 
> > ifconfig?
> 
> Not in any 'standard' card, no.  Some cards (in SUN workstations) allow
> you to swap the EEPROM with the mac address, and I'll bet somewhere
> someone has designed a card with a programmable mac address, but
> normally it's not settable.

while ifconfig might miss this functionality, i believe your answer
is incorrect. Several FreeBSD drivers read the MAC address from
the rom/eeprom, copy it to sc->arpcom.ac_enaddr, and write it back
to the card's address filter in the init phase. I suppose on other
systems the same thing happens. It's a software thing, not a hardware
one.

A quick check shows the following drivers do that:

	sys/i386/isa/if_ed.c
	sys/pci/if_fxp.c
	sys/pci/if_de.c (probably)

just to name the most common ones.

	cheers
	luigi

-----------------------------------+-------------------------------------
  Luigi RIZZO, luigi@iet.unipi.it  . Dip. di Ing. dell'Informazione
  http://www.iet.unipi.it/~luigi/  . Universita` di Pisa
  TEL/FAX: +39-050-568.533/522     . via Diotisalvi 2, 56126 PISA (Italy)

		  http://www.iet.unipi.it/~luigi/ngc99/
====  First International Workshop on Networked Group Communication  ====
-----------------------------------+-------------------------------------


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