Exploring IPv6

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Windows Server 2003 includes an IPv6 stack, in addition to the IPv4 stack, which you can use to explore the capabilities of IPv6, test new applications and network technologies, and plan the first steps toward the wider adoption of IPv6 on your network.

The current version of the Internet Protocol — IP version 4, known as IPv4 — dates from 1981 and has not changed substantially since it was introduced in RFC 791, "Internet Protocol." Although IPv4 proved to be remarkably robust and enduring, in the early 1990s the Internet Engineering Task Force (IETF) began to develop a suite of protocols and standards — IPv6 — to better address the demands of modern networking. Two of the most important of these protocols are RFC 2460, "Internet Protocol, Version 6 (IPv6) Specification," which defines IPv6, and RFC 2463, "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification," which specifies a set of ICMP messages for use with IPv6.

Before considering the design choices that you must make when introducing IPv6 on your network, you must become familiar with some of the basics about IPv6, including:

  • IPv6 features.

  • Supported features, server applications, and application programming interfaces (APIs).

  • Supported IPv6 tools.

  • Types of nodes.

IPv6 Features

The IPv6 protocol includes the following features and improvements over IPv4:

  • New header format. The IPv6 header is designed to minimize overhead. Although the IPv6 address field is four times as long as the address field in IPv4, the IPv6 header is only twice as large as the IPv4 header overall. The more efficient header design enables faster processing at intermediate routers. Because IPv6 headers are not interoperable with IPv4 headers, and the IPv6 protocol is not backward compatible with IPv4. A host or router must use an implementation of both IPv4 and IPv6 in order to recognize and process both header formats.

  • Large address space. IPv6 provides 128-bit IP addresses, in contrast with the 32-bit IPv4 IP addresses. The address space is designed to accommodate a vast number of interconnected devices on any network, and its structure is designed to reduce the number of routing table entries in IPv6 routers.

  • Hierarchical addressing and routing infrastructure. IPv6 global addresses are designed to facilitate a hierarchical routing infrastructure that is based on the common occurrence of multiple levels of ISPs. It is anticipated that the routing tables for backbone routers on the IPv6 Internet will be much smaller and, as a result, will be processed much more efficiently.

  • Automatic address configuration. IPv6 simplifies address configuration and renumbering by enabling automatic address configuration for all hosts. Host interfaces automatically learn their addresses through interactions with local IPv6 routers. They can learn new addresses on the fly, making network renumbering much simpler than in IPv4.

  • Integrated network security. Support for IPSec is an IPv6 protocol suite requirement.

  • Better support for Qualify of Service (QoS). The IPv6 header contains a new field that can be used to determine how to identify and prioritize traffic. Because the traffic type can be identified within the IPv6 header, support for QoS is available even when IPSec encryption is in use.

  • New protocol for neighboring node interaction. The IPv6 Neighbor Discovery protocol is a series of Internet Control Message Protocols for IPv6 messages (ICMPv6) that manage the interaction of nodes on the same link. Neighbor Discovery replaces broadcast-based Address Resolution Protocol (ARP), ICMPv4 Router Discovery, and ICMPv4 Redirect messages with efficient multicast and unicast Neighbor Discovery messages.

  • Extensibility. IPv6 can be easily extended to incorporate new features by adding extension headers after the IPv6 header. The size of IPv6 extension headers is limited only by the size of the IPv6 packets.

Supported Features, Server Applications, and APIs

Windows Server 2003 supports IPv6 functionality for a wide range of services. Table 1.3 shows which IPv6 features Windows Server 2003 IPv6 supports.

Table 1.3   IPv6 Features Supported by Windows Server 2003 IPv6

IPv6 Feature Supported by Windows Server 2003 IPv6


(Use Add protocol GUI, or use the Netsh command-line tool)



(Use Remove protocol GUI, or use the Netsh command-line tool)


Dual IPv6/IPv4 stack






6over4 (manual)


IPv6 NAT Traversal

(also referred to as Teredo)


DNS over IPv6

(also referred to as DNS AAAA records)


Linklocal Multicast Name Resolution (LLMNR)


DNS dynamic update




TCP PortProxy


Remote Desktop


Remote Assistance


IPv6 Management Information Base (MIB) for Simple Network Management Protocol (SNMP)


Microsoft Network Monitor version 2 (Netmon)


Visual Studio .NET (VS.NET)


IPSec authentication


IPSec encryption


Table 1.4 shows which server applications Windows Server 2003 IPv6 supports.

Table 1.4   Server Applications Supported by Windows Server 2003 IPv6

Server Applications Supported by Windows Server 2003 IPv6

File sharing, printer sharing


Windows Media Server


Internet Information Services (IIS) 6.0 (HTTP only)


Telnet server


FTP server


Active Directory


Microsoft® Exchange Server


SQL Server™


Windows Server 2003 IPv6 also supports Internet Explorer. However, it does not include support for literal addresses.

In addition, the following APIs support Windows Server 2003 IPv6:

  • .NET Framework

  • Windows Sockets 2 (Winsock2) API

  • Remote procedure call (RPC)

  • Distributed Component Object Model (DCOM)

  • Windows Internet (WinINet) API (does not include support for literal addresses)

  • Windows HTTP Services (WinHTTP)

  • HTTP.sys

  • IP Helper API (IPHLPAPI) module

  • Debuggers

Supported IPv6 Tools

Windows Server 2003 IPv6 supports the following tools.

  • Ping

  • Tracert

  • Pathping

  • Ipconfig

  • Route

  • Netsh (Use netsh interface IPv6 commands)

  • Netstat

  • Nslookup

  • Telnet client

  • FTP client

For more information about these TCP/IP tools and commands, see the Networking Collection of the Windows Server 2003 Technical Reference (or see the Networking Collection on the Web at http://www.microsoft.com/reskit).

Types of Nodes

To understand IPv6 tunneling technologies, such as 6to4 and ISATAP (described later), you must understand the types of nodes that might be involved. Table 1.5 shows IPv4 and IPv6 node types.

Table 1.5   IPv4 and IPv6 Node Types

Node Type Description

IPv4-only node

A device that can communicate only with IPv4 nodes and applications and that does not support IPv6.

IPv6-only node

A device that can communicate only with IPv6 nodes and that does not support IPv4.

IPv6/IPv4 node

A device that implements both IPv4 and IPv6 and that can communicate with either IPv6 or IPv4 nodes and applications.

IPv4 node

Any device that supports IPv4. Both IPv4-only and IPv6/IPv4 nodes are IPv4 nodes.

IPv6 node

Any device that supports IPv6. Both IPv6-only and IPv6/IPv4 nodes are IPv6 nodes.

For more information about the different node types, see RFC 2893, "Transition Mechanisms for IPv6 Hosts and Routers."