When a Web client such as Internet Explorer or Netscape sends a request to a server for a Web page, the client typically does so using the fully qualified host name of the server, such as

When Internet Information Services (IIS) receives the request, it examines the host header in the request to determine how it should respond. For example, in the request for, the host header is IIS looks in the properties for the sites it maintains and serves the one that matches.

Each Web site in IIS has three identifying properties: IP address, port, and host header. At least one of these properties must be unique for each site. For example, multiple sites on the same server can use the same IP address and port, but each must have a unique host header. To direct traffic to a specific Web site, specify the appropriate host header in the site's properties.

For example, perhaps local clients can't access an internal Web site because of the way the firewall handles in-network requests for the server's public IP address. Rather than change the firewall configuration, add a DNS host record named local that points to the local IP address of the server.

Then, modify the properties of the site to add local.yourdomain.tld to the site, specifying your own public Internet domain in place of yourdomain.tld. Local clients can then connect to http://local.yourdomain.tld/ to access the site from behind the firewall.