"This article discusses a network setup where multiple webservers reside behind one IP address. Such a situation may arise when you need a specific webserver for one task and a different webserver for another task, running different operating systems or webserver software. With only one IP address available from the Internet, you could simply use Network Address Translation (NAT) with port forwarding. However, this forces you to give each webserver an ugly URL with a non-standard port number. Luckily, there is a better way. In the setup described in this article, each webserver can be reached via its own fully qualified domainname on the standard HTTP port (80)."