> Can one of you network gurus explain how this is legal, by 
> Ethernet specs?  
> I'm a little out of date, but MAC addresses were supposed to 
> be sacrosanct physical IDs that are unique for each card.  Of 
> course this was late 70's or early 80's, and there was no 
> danger of running out of them!

Yes, that's true, they are supposed to be unique for every card, but some
manufacturers have produced so many cards that they have had to repeat
addresses.  However, it is sometimes useful to be able to change them.  For
example, if you have a redundant firewall setup using the HA stuff for linux
and one firewall fails and you have to switch over to the other one, you
have to change the MAC addresses also to prevent any interruption in network
service, at least when using cisco routers.  

It's also useful for when certain vendors have a software license that looks
at the MAC address in your machine to be able to run.  When that vendor
charges 12 times as much for their NIC's with the new software license file,
and you can get by with a $50 replacement NIC and use of the "ifconfig ethX
hw ether <MAC>" commmand, it comes in very useful.  You cannot however have
two NICs with the same MAC on the same LAN at one time.  You've been able to
manually change the MAC address in IBM's AS/400 stuff for many years now.

Jay