Spoofing a MAC Address in FreeBSD
(Borrowed from O'Reilly's "BSD Hacks")

- Use `ifconfig` to determine the MAC of your current NIC
	(If you're wanting to borrow its MAC to use on another device)
	# ifconfig xl0
		ether 00:50:04:72:1a:aa

- If your ISP uses DHCP, find out the identifier used by their server
	# more /var/db/dhclient.leases | grep host
		option host-name "00-50-04-72-1a-aa-36-33"
		(Some ISPs use option host-name, other's use dhcp-client-dentifier)

- Spoof the MAC
	# ifconfig xl0 ether 00:50:04:72:1a:aa

	Verify:
	# ifconfig xl0 | grep ether

- To survive a reboot, edit /etc/rc.conf:
	ifconfig_xl0_alias0="ether 00:50:04:72:1a:aa"
	(Or leave out the alias if you wish)

- Edit /etc/dhclient.conf
	interface "xl0" {
		send host-name "00-50-04-72-1a-aa-36-33";
		send dhcp-client-identifier "00-50-04-72-1a-aa-36-33";
	}

- Restart the network
	# /etc/netstart

- Release your DHCP info
	# dhclient -r xl0
		
	
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You should be familiar with *NIX networking before doing this.
I don't go into detail, obviously, and you should know what each command does.