I've been using Virtual Box for a while and love it. But the downside of vbox is you can not use your NIC's alias as the bridge or interface. So, I found out a way to add a bridge NIC in pure command mode. Since there is no such tutorial online, I would love to write this down and share with you. This is just a short tutorial that to show you create a virtual NIC in command lines only.
brctl addbr virbr2
ifconfig virbr2 up
# now, record the MAC address of your Virtual NIC
# and type all following lines in there,
# but modify 'HWADDR' as the MAC address
# and change the IP as you want.
# now, check if it's really working
# if it's successfull, the ip you typed before should be assigned
service network restart
then, your virtual NIC should be up and running after restart.
PS: i put a long title on purpose, so other people can google it. :-)