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From: Theo <theom+news@chiark.greenend.org.uk>
Newsgroups: comp.sys.raspberry-pi
Subject: Re: Duplicate MAC addresses
Date: 13 Jul 2022 10:41:46 +0100 (BST)
Organization: University of Cambridge, England
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Marco Moock <mo01@posteo.de> wrote:
> Please check if they really have the same MAC address when booted from
> a new installed OS. It is possible to change the MAC address.
> The MAC address of the physical interface (not any virtual interface)
> should have an unique MAC address by default from the vendor.
> You can override this if they really have the same MAC by default.

Are the MAC addresses in the Broadcom MAC address allocation - I think it
starts B8: ?

(a Pi 3 here has B8:27:EB)

I vaguely understood that pre-Pi4 there's no nonvolatile storage on the
board to hold the MAC address, so I believe it's generated programmatically
in the boot process (from the serial number, I presume).  It would seem
surprising to have a collision.

The Pi4 has a proper EEPROM holding the boot firmware so there's scope to
store the MAC in there - I haven't checked they do that though.

Theo