More than 87% of active domain names are found to share their IP addresses (i.e. their web servers) with one or more additional domains, and more than two third of active
domain names share their addresses with fifty or more additional domains. While this IP sharing is typically transparent to ordinary users, it causes complications for those who seek to filter the Internet, restrict users' ability to access certain controversial content on the basis of the IP address used to host that content. With so many sites sharing IP addresses, IP-based filtering efforts are bound to produce "overblocking" -- accidental and often unanticipated denial of access to web sites that abide by the stated filtering rules.
A single IIS server can host multiple web sites and normally each web site is tied to a IP address however if the machine only has one IP address it can still be configured to host multiple web sites by specifying a host header name for each web site as follows (you should first ensure you have multiple DNS entries all pointing to the IP address of the machine):
1)Start the Internet Information Services MMC snap-in (Start - Programs - Administrative Tools - Internet Information Services)
2)Expand the server
3)Right click on the web site and select Properties
4)Next to the IP address (ensuring the actual IP address is selected) click the Advanced button
5)Select the IP address entry and click Edit
6)Enter the DNS host entry for the web site and set the port to 80
7) Click OK Click OK to the main dialog
8)Repeat for all other web sites
9)When the client connects the DNS name requested is passed in the header as the host name and that is what is mapped.
If the Web site requested in the host header is stopped, the client receives the default Web site. Therefore, it is recommended that an ISP use the default Web site as the ISP home page, rather than for a customer site. Multiple sites on a single Professional installation is not supported.
Also do not configure a header host name for the default web site as this may cause problems for other packages such as Proxy Server which expect the default web site to use port 80, IP address of "All Unassigned" and no host header name.