Have a look at the link in my 1st reply.
It's showing how you can add the extra IP(s), so that they are virtual ones.
I've got 8 IP's setup that way on my system.
One for FTP, one for the normal HTTP stuff, 3 for DNS, one for POP3, one for SMTP, and one for remote stuff.
With the firewall I'm manageing the IP's and correct ports for it.
So.. If I scan the "FTP" IP, I only see the needed FTP ports open. If I scan the DNS IP, I only see the needed DNS port open.. etc. etc.
Never execute code written on a Friday or a Monday.