Host-Header Routing

Applies To: Windows Server 2003 with SP1

You can use one IP address (or the All Unassigned setting) for multiple Web sites and distinguish the Web sites with unique host-header names. This option is easy to configure by using IIS Manager. To use host-header names, your computer or network must be using a name resolution system such as DNS.

When a client sends a request for an HTTP connection to the server running IIS, the client request includes a field in the HTTP header called HOST. This field contains the host name of the requested Web server. For example, when you type https://www.microsoft.com into your browser, your browser sends a packet with an HTTP header that includes the following field: HOST: www.microsoft.com. Because the name of the field is HOST and it is in the HTTP header of the client, it is referred to as the host header. For more information on the HTTP 1.1 standard, see the RFC 2616, Hypertext Transfer Protocol -- HTTP/1.1 on the Internet Engineering Tasks Force Web site.

With host-header routing, when a client request reaches the server, IIS uses the host name, rather than only the IP address as it does with IP–based routing, to determine which Web site the client is requesting. To set up multiple Web sites on the same server to take advantage of host-header routing, the host-header names must be DNS domain names that are publicly available and registered with an authorized Internet naming authority. For more information about obtaining a DNS name, see DNS Overview_IIS_SP1_TechRef.

Host-Header Routing and SSL

Beginning with Windows Server 2003 Service Pack 1 (SP1), IIS supports the use of SSL with host header routing. For more information about setting up host headers for an SSL-enabled Web site, see Configuring SSL Host Headers.