Create Additional Virtual Network Devices?

Is there a way to create another network interface on my Mac, with it's own (fake) MAC address?

I know I can do the following:

ifconfig alias en1 10.0.0.3

Then I will have that IP address in addition to my existing IP address. But I want to make another interface so it looks like there are two machines on the LAN instead of one machine with 2 IP's

I know when I create a VM in VirtualBox, if I used bridged networking it makes the virtual look like an entirely different computer on the network, with it's own IP address and MAC address.