A server can use IIS versions 4.0 and later to host multiple Web sites, and this is possible by using any of the following methods:
- By using different IP addresses, but the same port number.
- By using the same IP address, but different port numbers.
- By using the same IP address and port number, but using HTTP 1.1 host headers.
When a request comes to the server by using SSL, IIS looks in its configuration store to determine which certificate to use. This is accomplished by completing a lookup on the IP/port combination. Under the following conditions, the typical progression of events is to view the host header to determine which Web server to use:
- There are multiple Web servers on a computer that are all assigned the same IP address and port number.
- The computer is configured to use host headers.