Windows 7 / Networking

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Planning an IP transition

Many enterprise administrators are so comfortable working with IPv4 addresses that they are hesitant to change. Network Address Translation (NAT) and CIDR have been excellent stopgaps to the depletion of the 32-bit IP address space for years, and many would like to see them continue as such. However, the IPv6 transition, long a specter on the distant horizon, is now suddenly approaching at frightening speed, and it is time for administrators not familiar with the new technologies to catch up or be left behind.

The networking industry, and particularly the Internet, has made huge investments in IPv4 technologies, and replacing them with IPv6 has been a gradual process. In fact, it is a gradual process that was supposed to have begun in earnest over ten years ago. However, many people treat their IPv4 equipment like household appliances: Unless it stops working, there is no need to replace it. Unfortunately, the day when that equipment stops working is approaching rapidly. So, although it might not yet be time to embrace IPv6 exclusively, administrators should have the transition in mind as they design their networks and make their purchasing decisions.

The exhaustion of the IANA unallocated address pool occurred on January 31, 2011. One of the RIRs, the Asia Pacific Network Information Center (APNIC), was depleted on April 15, 2011, and the other RIRs are expected to follow suit before long.

Enterprise administrators can do as they wish within the enterprise itself. If all of the network devices in the organization support IPv6, they can begin to use IPv6 addresses at any time. However, the Internet is still firmly based on IPv4, and will continue to be so for several years. Therefore, a transition from IPv4 to IPv6 must be a gradual project that includes some period of support for both IP versions.

At the present time, and for the immediate future, administrators must work under the assumption that the rest of the world is using IPv4, and you must implement a mechanism for transmitting your IPv6 traffic over an IPv4 connection. Eventually, the situation will be reversed. Most of the world will be running IPv6, and the remaining IPv4 technologies will have to transmit their older traffic over new links.

Using a dual IP stack

The simplest and most obvious method for transitioning from IPv4 to IPv6 is to run both, and this is what all current versions of Windows do, going back as far as Windows Server 2008 and Windows Vista.

By default, these operating systems install both IP versions and use them simultaneously. In fact, even if you have never heard of IPv6 until today, your computers are likely already using it, and have IPv6 link-local addresses that you can see by running the ipconfig /all command.

The network layer implementations in Windows are separate, so you configure them separately. For both IPv4 and IPv6, you can choose to configure the address and other settings manually, or use autoconfiguration.

Because Windows supports both IP versions, the computers can communicate with TCP/IP resources running either IPv4 or IPv6. However, an enterprise network includes other devices also, most particularly routers, that might not yet support IPv6. The Internet also is nearly all still based on IPv4.

Beginning immediately, administrators should make sure that any network layer equipment they purchase includes support for IPv6. Failure to do so will almost certainly cost them later.