Planning and Design Considerations
Because the infrastructure, servers, and clients that comprise the modern Internet are managed by millions of different people and organizations, it will take many years before networks have entirely transitioned to IPv6. In the meantime, IPv4-to-IPv6 transitioning technologies allow hosts to communicate with different parts of the network.
The most important transitioning technology is the ability for hosts to use both IPv4 and IPv6 simultaneously. Windows Vista and Windows Server 2008 have both IPv4 and IPv6 enabled by default for all network adapters.
This section provides information to evaluate IPv6 and ...