The release of Windows Server 2008 introduced several industry standards built in to the Windows operating system that have since been updated in Windows Server 2008 R2. These changes continue a trend of the Windows operating system supporting industry
standards rather than proprietary Microsoft standards. One of the key standards built in to Windows Server 2008 and Windows Server 2008 R2 is IPv6.
Internet Protocol version 6 (or IPv6) is the future Internet standard for TCP/IP addressing. Most organizations support Internet Protocol version 4 (or IPv4). Due to the Internet numbering scheme running out of address space in its current implementation of addressing, Internet communications of the future need to support IPv6, which provides a more robust address space.
Additionally, IPv6 supports new standards in dynamic addressing and Internet Protocol Security (IPSec). Part of IPv6 is to have support for the current IPv4 standards so that dual addressing is possible. With Windows Server 2008 R2 supporting IPv6, an organization can choose to implement a dual IPv6 and IPv4 standard to prepare for Internet communications support in the future.
Source of Information : Sams - Windows Server 2008 R2 Unleashed