HOW TO: Use Host Header Names to Host Multiple Sites from One IP Address in IIS 5.0

SUMMARY

This step-by-step article shows you how to use Host Headers to allow multiple host names to share a single IP address.

IIS allows you to assign any number of sites to a single IP address and distinguish them by using host headers. When IIS receives a request for a Web page, it looks at the information sent in by the browser. If the browser is HTTP 1.1 compliant (Internet Explorer 3.x and later, or Netscape Navigator 3.x and later), the HTTP header contains the actual domain name requested. IIS uses this to determine which site should answer the request.

If the browser is not HTTP 1.1 compliant, you can program a core page to display all sites available and allow the user to choose which site to use. For instructions on how to do this, see the references section at the bottom of this article.

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Configure Host Header Names in IIS 5.0

To configure host header names in IIS

1. Start the Internet Service Manager (Iis.msc).
2. Right-click the Web site to be configured, and then click Properties.
3. On the Web Site tab, select the IP address that the site will use.
   
   Note: if you only have one IP address on the server, select All Unassigned, and set the TCP Port that should be used (usually 80).
4. Click Advanced.
5. In the Multiple identities for this Web Site list, select the identity that you want to use.
6. Click Edit, and then add the desired host header name.
   
   NOTE: If you want this site to respond to more than one host header name, use the Add button to add additional identities to this list. Specify a different host header name for each identity, but be sure to use the same IP address and port.
7. Apply these changes and start the Web site (if it is not already running).
8. Register the host header name with the appropriate name resolution system.
   
   If the computer is on an intranet (a private LAN that uses Internet technology), register it with the intranet's name resolution system, such as the Windows Internet Name Service (WINS).
   
   If the computer is on the Internet, register the host header name with the Domain Name System (DNS), which is administered by InterNic.
9. After the host header name is registered with the name resolution system, test it from a browser by attempting to browse the host header name. The browser should open the expected Web site.

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Troubleshooting

• When your computer boots or when you manually start the Microsoft Internet Information Server service, Event Viewer may log the following event:

  Event ID : 115
  Source : w3svc
  Description : The service could not bind instance X.

  This problem can occur when some or all of the Web sites that are using Host Headers have the same port number defined for Secure Sockets Layer (SSL). Internet Information Server 4.0 does not support the use of Host Headers for SSL. For more information, see the references links below.
• Erratic behavior can occur when applying a host header name to the default Web site if add-on packages for IIS (such as Microsoft Proxy Server) are also being used. For this reason, it is generally not recommended that you apply a host header name to the default Web site created by IIS.

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