Using Host Header Names to Host Multiple Sites from 1 IP Address

Last reviewed: November 17, 1998
Article ID: Q190008

The information in this article applies to:

Microsoft Internet Information Server version 4.0

SUMMARY

Host header names can be used to host multiple domain names from one IP address. To do this, perform the following steps:

Start the Internet Service Manager (ISM), which loads the Internet Information Server (IIS) snap-in for the Microsoft Management Console (MMC).
Right-click the Web site that should use a host header name, and then click Properties on the shortcut menu.
On the Web Site tab, select the IP address that the site should use (if you only have one IP address on the server, select All Unassigned), and set the TCP Port that should be used (usually 80).
Click Advanced.
In the "Multiple identities for this Web Site" list, select the identity that you want to use.
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.
Apply these changes and start the Web site (if it is not already running).
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.
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.

WARNING: Do not use a host header name with the default Web site. This can cause erratic behavior with add-on packages for IIS (such as Microsoft Proxy Server) that expect the default Web site to use the IP address of "All Unassigned", TCP port 80, and have no host header name.

MORE INFORMATION

To distinguish one Web site from another on the same computer, IIS uses the following three elements:

TCP/IP address
TCP port
Host header name

As long as at least one of these three items is unique for each Web site, IIS can manage multiple sites.

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 (for example, 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.

For additional information, see the following topics in the Windows NT Option Pack documentation:

Microsoft Internet Information Server

    - Server Administration
       - Name Resolution
          - About Name Resolution

Microsoft Internet Information Server
```
    - Server Administration
       - Web and FTP Sites
          - Naming Web Sites
```
If the browser is not HTTP 1.1 compliant, there is a way to 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, refer to the following documentation:
- Microsoft Internet Information Server
```
    - Server Administration
       - Web and FTP Sites
          - Supporting Host Header Names in Older Browsers
```
For additional information, see the following article in the Microsoft Knowledge Base:
```
   ARTICLE-ID : Q186810
   TITLE      : Event ID 115 When Using Host Headers With IIS
```

Multiple e-mail domains to one IP address can be done easily with correct configuration of the MX records in the DNS and your mail server. To the best of my knowledge the best you can do is DNS multiple domains to the same IP and restrict access for each user login for particular directories i.e.

ftp.customera.com -> 10.100.10.90

ftp.customerb.com -> 10.100.10.90

When customera logs on to ftp.customera.com then his initial directory will be /customera and this will be the only directory he has access to. The same setup for customerb

This is covered well in the NT 4.0 Option Pack online documentation.

You create "host header names". In the MMC Internet Service Manager, select the server name under IIS, and do the New action to get to New Website. Then you assign the IP address of the computer and port 80 and the home directory for the web site.

Then you have to create a CNAME DNS entry for the website name that you want to use which points to the NT Server name where the website resides (NOT the default web server name).