If you think migrating to IPv6 is as simple as upgrading to Microsoft Windows Vista, think again.

Vista is the first operating system from Microsoft that automatically installs and enables IPv6, the long-anticipated next generation of IPv4, the Internet's main communications protocol. Even the biggest proponents of Vista, however, say enterprise customers will find rolling out the software's IPv6 capabilities is difficult and time-consuming.

That's why Microsoft executives are urging corporate network managers to start testing Vista's dual-TCP/IP-stack IPv6 implementation, which supports both IPv4 and IPv6 traffic, at least a year before putting it on a production network.

"This is a large upgrade. We're really looking at a lot of different moving parts. It's not just a matter of flipping a switch and everything works," says Sean Siler, IPv6 program manager for Microsoft. "Not everything supports IPv6 throughout the entire network infrastructure. You have to make sure you have the right management tools and the right security tools. It's a good thing to do a network inventory."

Chris Mitchell, Microsoft's group program manager responsible for the implementation of TCP/IP in Windows, says if network managers don't spend enough time familiarizing themselves with all the changes in IPv6, they'll fail to take advantage of the protocol's benefits.

"It's easy to say that IPv6 gives you a larger address space and everything else works the same," Mitchell says. "As a practical matter, that's not the way it is. If you do that, you will potentially repeat some of the limitations of IPv4."

IPv6 features a virtually limitless address space. IPv4, on the other hand, supports about 3.4 billion IP addresses, which are being exhausted rapidly. When all IPv4 addresses have been handed out, service providers and enterprises will need to support IPv6 on their networks.

IPv6 also has IPSec built-in security and supports autoconfiguration of network devices. Another benefit: The end-to-end connectivity it provides will enable many new applications, such as wireless, mobile streaming multimedia and data-intensive mash-ups.

Microsoft is taking a long-term view with regard to migrating its business customers to IPv6. The company says all its enterprise-class software will support IPv6 by the next major release. "IPv6 is the future, and we want to make sure that it is supported in the product sets we build," Siler says. "We wanted to make sure that Windows as a platform would provide all the connectivity that our customers are going to need today and in three to five to seven years."

Both Windows Vista and Windows Server 2008 support IPv6 by default and prefer IPv6 to IPv4. While IPv6 is enabled automatically on the Vista client software, network managers must choose to route their networks via IPv6 or IPv4. "Once a network manager makes the decision to go to IPv6, they would make a conscious effort to start routing IPv6 through one of several different methods, and they can start enabling one small subnet at a time," Siler says.