As you begin to evaluate the role of Internet Protocol version 6 (IPv6) on your intranet and start planning for its deployment, you should understand how IPv6 traffic is supported over virtual private network (VPN) connections in Windows. With VPN connections, you can extend your network to include links across public networks such as the Internet. VPN connections are protected by strong authentication protocols to validate the credentials of the connecting user, and encryption methods to provide data confidentiality.

Windows® XP and Windows Server® 2003 include an IPv6 protocol stack, but many core services and networking components do not support IPv6. Windows Vista™ and Windows Server 2008, formerly code-named "Longhorn," have full-featured support for IPv6, which is installed and enabled by default. In fact, almost all of the networking applications and services included with Windows Vista and Windows Server 2008 support IPv6. This month, I examine the support in Windows Vista, Windows Server 2008, Windows XP, and Windows Server 2003 for IPv6 traffic sent over VPN connections that are established across the Internet Protocol version 4 (IPv4) and IPv6 Internets.