Increasingly MAC addresses are being stored in NVRAM.


John Clark, Software Engineer
mailto:JohnC@inter-intelli.com
(317) 715-8175 (voice & fax)

Interactive Intelligence, Inc.
3500 DePauw Blvd., Suite 1060
Indianapolis, IN  46268-1136
http://www.inter-intelli.com

> -----Original Message-----
> From: Bob Drzyzgula [SMTP:pic@DRZYZGULA.ORG]
> Sent: Tuesday, March 30, 1999 10:29 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [OT] Network Card Address
>
> It depends a fair bit on the OS as to whether you can do
> this.
>
> You generally cannot pre-specify the MAC address on a
> card; the entire point of the MAC address system is to
> have guaranteed-unique device IDs.  (MAC being "media
> access control", and the MAC address consisting of a
> three-byte OUI -- organizationally unique identifier --
> followed by the three-byte device ID; the OUI is that of
> the card manufacturer, and is assigned by the IEEE.)
>
> However, the MAC address is stored in ROM on the card
> and read in by the driver in the operating system,
> which generally will then uses the in-memory copy
> of the address in formatting and receiving packets.
> Depending on the sophistication of the driver and
> the utilities made available by the OS, you may be
> able to override the MAC address on the card; the
> OS driver will then just use the MAC address you tell
> it to instead of the one on the card. In most
> UNIX systems, this is implemented as an option on
> the ifconfig command.
>
> This won't make your two systems look identical from
> a hardware standpoint, but if you always override
> the MAC address on both machines, then you will be
> able to make them functionally identical from a
> whole-system perspective. This probably won't help
> you if you need to net-boot those machines, unless
> you have some fancy cards (I don't know of any that
> will do this) that will let you override the MAC
> address in firmware. You may be able to do this on
> a Sun in the Open Boot Prom, but you weren't talking
> about Suns.
>
> --Bob
>
> On Tue, Mar 30, 1999 at 09:55:03AM -0500, Montaigne, Mike wrote:
> > I need two network cards with the same address,
> > Does anyone where I can buy two/another card
> > with a specified address?
> >
> > I want to set up two PC's to look exactly the same.
> >
> > tks
> >
> > Mike
>
> --
> ============================================================
> Bob Drzyzgula                             It's not a problem
> bob@drzyzgula.org                until something bad happens
> ============================================================