I use CARP VIPs for 2 reasons. It is better than ProxyARP in some ways, and in the future, I can setup clustering without have to redo IP alias or ProxyARP. If you are never going to cluster, then IP alias VIPs would be the way to go IMO. Once you have the VIP setup, then you can setup NAT and the rules. There is 1:1 NAT or port mapping. port mapping allows for potentially more internal servers as you can put different ports on different servers. There is a book and a document repo that you can use to help you with the setup.