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Date:      Tue, 18 May 1999 09:09:37 +0100
From:      "Steve Gailey" <Steve.Gailey@db.com>
To:        hackers@freebsd.org
Subject:   Re: ifconfig: changing mac address
Message-ID:  <199905180812.JAA08915@pow.srv.uk.deuba.com>
In-Reply-To: <Pine.LNX.4.10.9905141201420.7240-100000@ftp.scientech.com>
References:  <199905141729.LAA11747@mt.sri.com>

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My experience is that most modern (and many older) PC NIC's are 
able to change their MAC address. The question really is, how 
should I do this from within FreeBSD.

Is there a standard entry into the drivers to do this?

If you are wondering why I want to do this, I am looking at hot 
standby and redundant takeover stuff for high availability systems.

Steve

> On Fri, 14 May 1999, Nate Williams wrote:
> > > I know it's possible to bridge ethernet segments under linux, and the
> > > only way that bridging can be implemented is if the MAC address be
> > > changed in software on a per-packet basis.
> > 
> > What do you mean 'bridge ethernet segments'?
> 
> A bridge will listen on two specific ethernet ports and decide which MAC
> addresses are on which side of the bridge and only forward those packets
> which need to cross the bridge.
> 
> In addition, bridges use the IEEE spanning protocol to get rid of possible
> loops when there are multiple bridges and switches connected together.  An
> ethernet switch is in essence a bridge with alot of ports.
> 
> > 
> > > Very likely there are not kernel facilities to do this, but the
> > > existence of bridging code convinces me that it must be possible to
> > > alter mac address.
> > 
> > Not that I'm aware of.  Too many licensing schemes rely on mac addresses
> > to provide the unique 'fingerprint' to have this be something that is
> > easily doable.
> > 
> 
> You're too stubborn here.  If a linux box can bridge, then it logically
> must be able to change MAC address on a per-packet basis.
> 
> Also when a PC runs a DECNET client, it must also be able to change
> ehternet addresses from the base value in the card.
> 
>   -- C. Mott
> 
> 




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