You can set up URL-host-based virtual servers by giving them unique URL hosts. The contents of the Host request header directs the server to the correct virtual server.
For example, if you want to set up virtual servers for customers aaa, bbb, and ccc) so that each customer can have an individual domain name, you first configure DNS to recognize that each customer’s URL, www.aaa.com, www.bbb.com, www.ccc.com , resolves to the IP address of the listen socket you are using. You then set the URL hosts for each virtual server to the correct setting (for example, www.aaa.com).
Because URL-Host-based virtual servers use the Host request header to direct the user to the correct page, not all client software works with them. Older client software that does not support the HTTP Host header does not work. These clients will receive the default virtual server for the listen socket.