Background on Host Headers

IIS supports multiple web sites on a single server via three different methods, assigning each site a unique IP address, assigning each site a different TCP port number or the preferred way is using the host header name.

When a users connects to a web server the name of the host they are trying to get to is included in the packet, IIS (and other web servers) can use this field to direct the user to a certain web site hosted on the server.