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Internet Protocol Version 6 Features

Updated: August 22, 2005

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1

This version of IIS provides Internet services to clients connecting over the next generation of Internet Protocol (IP) known as IP version 6, or IPv6. IPv6 is included with the Microsoft Windows XP networking platform and the Microsoft Windows Server 2003 family.

The Internet Server API (ISAPI) framework provides the appropriate local- and remote-host server variables for IPv6 network addresses: LOCAL_ADDR and REMOTE_ADDR. When clients connect over IPv6, these variables store the IPv6 address.

When writing applications that use the ISAPI server variables for network addressing over IPv6, remember that all buffers allocated for network address storage can be a maximum of 128 bits in size (56 character string), whereas buffers allocated for network address storage over IPv4 are limited to 32 bits (16 character string).

After the protocol stack is installed, IIS automatically begins supporting IPv6 on your Web server.

Web sites that are already running must be restarted before they begin listening for IPv6 requests. Sites created after IPv6 support is enabled automatically listen for IPv6.


The IIS core functionality has not changed as a result of IPv6 support; however, only a subset of all IIS 6.0 functionality is available for IPv6.

  • IIS Manager does not display IPv6 addresses as it does for IPv4 addresses.

  • Bandwidth Throttling is not supported for IPv6 Web sites.

  • The ServerBindings metabase property does not support storing IPv6 literal addresses (as defined in RFC 2732). This behavior limits IIS to support host-header routing only.

  • The IP Address Restrictions feature in IIS does not support IPv6 addresses or IPv6 prefixes.

  • The EnableReverseDnsLookup metabase property is not supported. Setting this property to true does not cause the REMOTE_HOST server variable to return the DNS name of the client, as it does for IPv4. REMOTE_HOST will always contain the IPv6 address regardless of the EnableReverseDNSLookup setting.

  • Site routing based on IP addresses is not supported for IPv6. Server address with sites that are configured to route based on IPv4 addresses will not respond to IPv6 requests.

  • IPv6 is enabled for all sites. You cannot configure IPv6 support at the machine level. In other words, you cannot configure individual sites to respond to IPv6 traffic while other sites on the same server respond to IPv4 traffic. It is possible, however, to limit IPv6 traffic to a specific site if that site is configured to use IP-based routing on an IPv4 address.

  • Logging. IIS writes IPv6 addresses to the log file when IPv6 is enabled and client computers connect to the server using IPv6 addresses. Log parsing tools must support IPv6 address formats if they are to be used with log files for IPv6 sites.

  • SSL. Due to the IP routing restriction for IPv6, IIS deployments designed for IPv6 addresses are limited to one Secure Sockets Layer (SSL) site per computer.

Related Information

  • For information about how to install the IPv6 network protocol stack, see IPv6 and IIS 6.0.

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