I don't understand why you need multiple mac addresses.
It boils down to wanting 5 routable IP's and the nasty cable company require one MAC for each IP they assign. There is no rational reason for this, but they're addimant.
Maybe if we understood the goal of what you were trying to accomplish, we might be able to help better.
Does it make more sense now?
If you just want to have multiple machines behind the firewall, just use NAT and non-routable IP addresses (192.168.x.x).
That's not it at all.
-- </chris>
