netdev - Re: [net-next PATCH] igb: Use Intel OUI for VF MAC addresses

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Date:	Thu, 10 Sep 2009 20:02:43 -0700
From:	Joe Perches <joe@...ches.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>, davem@...emloft.net,
	netdev@...r.kernel.org, gospo@...hat.com,
	Greg Rose <gregory.v.rose@...el.com>,
	Don Skidmore <donald.c.skidmore@...el.com>
Subject: Re: [net-next PATCH] igb: Use Intel OUI for VF MAC addresses

On Thu, 2009-09-10 at 19:07 -0700, Stephen Hemminger wrote:
> On Thu, 10 Sep 2009 18:48:27 -0700
> Jeff Kirsher <jeffrey.t.kirsher@...el.com> wrote:
> > From: Gregory Rose <gregory.v.rose@...el.com>
> > This patch changes the default VF MAC address generation to use an Intel
> > Organizational Unit Identifier (OUI), instead of a fully randomized
> > Ethernet address.  This is to help prevent accidental MAC address
> > collisions.

I think this not a very good idea.

> How can probability of collision be lower when the address space
> is smaller? If you are going to use Intel OUI, then you should constrain
> the selection to a portion of that space that is not being used
> by other hardware. I.e if you know Intel assigns addresses to their
> devices in ranges, choose a range that is not in use.

Some other possibilities might be:

o Apply for a Linux specific OUI, maybe via the Linux Foundation,
  and assign MAC random addresses using only that OUI.
o Avoid assigning random MAC addresses that use the initial values
  of already assigned OUIs.

  http://standards.ieee.org/regauth/oui/oui.txt

  Unfortunately, this is not a complete list because several
  vendors have just picked a number at random.

  Nominally assigned leading bytes are:

  00 02 04 08 0C
  10 11 14 18 1C
  20 24 28
  30 34 3C
  40 44 48
  58
  60 64 68 6C
  70 74 78 7C
  80 88
  90 94 98 9C
  A0 A4 A8 AA AC
  B0 B4 B8 BC
  C0 C4 C8 CC
  D4 D8 DC
  E0 E4 E8 EC
  F0 F4

  Maybe just pick an unused specific leading byte.


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