Administering an ISP Installation

One Computer, Same IP Address, Multiple Hosts

IIS 4.0 introduced host header names as a way to create many sites very quickly, without the need for IP addressing or subnet calculations. The advantage of host headers is that an Internet browser can access the IIS 5.0 Web server with a known URL (for example, reskit3.microsoft.com). The IIS 5.0 server will then map that URL path to an established location that matches each Web site’s host header name. With this option, it is very easy (through the IIS snap-in) to create new sites, define their home pages, allocate bandwidth, and set specific access rights.

The following example shows two Web sites (reskit3.microsoft.com and reskit4.microsoft.com) hosted on one computer with the same IP address (172.21.13.45). In this case, the host header names differentiate between the sites.

CLIENT REQUEST FOR reskit3.microsoft.com
IP: Destination Address = 172.21.13.45
HTTP: Request Method = GET
HTTP: Uniform Resource Identifier = /
HTTP: Protocol Version = HTTP/1.1
HTTP: Accept = image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/vnd.
HTTP: Accept-Language = en-us
HTTP: Accept-Encoding = gzip, deflate
HTTP: User-Agent = Mozilla/4.0 (compatible; MSIE 5.0; Windows 2000)
HTTP: Host = reskit3.microsoft.com
HTTP: Connection = Keep-Alive

CLIENT REQUEST FOR reskit4.microsoft.com
IP: Destination Address = 172.21.13.45
HTTP: Request Method = GET
HTTP: Uniform Resource Identifier = /
HTTP: Protocol Version = HTTP/1.1
HTTP: Accept = image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/vnd.
HTTP: Accept-Language = en-us
HTTP: Accept-Encoding = gzip, deflate
HTTP: User-Agent = Mozilla/4.0 (compatible; MSIE 5.0; Windows 2000)
HTTP: Host = reskit4.microsoft.com
HTTP: Connection = Keep-Alive

For information about setting up host headers, see the “Naming Web Sites” topic in the IIS 5.0 online product documentation. For a general discussion about name resolution and IP addresses, see the “Name Resolution” topic in the IIS 5.0 online product documentation.