Cisco has quietly begun serving up content from its main website that supports IPv6, the long anticipated upgrade to the Internet's main communications protocol known as IPv4. The move is significant given that Cisco has been selling IPv6-enabled routers, software and services to carriers and enterprise customers for many years. Now, Cisco is taking the initiative to deploy IPv6 on its own public-facing website, which the IT industry calls "dogfooding", when a company deploys its own technology.

Cisco confirmed Tuesday that on August 23 it began testing IPv6 on an alternative website,, instead of its main website, which is Cisco said it is maintaining a dual IPv6 and IPv4 approach for its external web presence so that all of its customers can access the website reliably.

"We could begin with a translating proxy to give an IPv6 presence with an IPv4 back end, but since the end goal is native IPv6 anyway we have decided to take this time to get our applications steadily moved to IPv6 natively rather than translating," explains Mark Townsley, distinguished engineer for Cisco. "We may consider a proxy for some parts of our presence down the road, but for the moment we prefer working on the various IPv6 dependencies in our code directly."

Cisco isn't the only IPv6 vendor to have dragged its feet on deploying the new IP addressing standard on its website. Microsoft, which offers built-in IPv6 in Windows 7 and Windows Vista, has yet to support IPv6 content on Bing or MSN.

IPv6 is the biggest upgrade in the 40-year history of the Internet. Forward-looking carriers and enterprises are deploying IPv6 because the Internet is running out of IP addresses using the current standard, known as IPv4. IPv4 uses 32-bit addresses and can support 4.3 billion devices connected directly to the Internet. IPv6, on the other hand, uses 128-bit addresses and supports a virtually unlimited number of devices, 2 to the 128th power.

About 94.5% of IPv4 address space has been allocated as of September 3, 2010, according to the American Registry for Internet Numbers (ARIN), which delegates blocks of IPv4 and IPv6 addresses to carriers and enterprises in North America. Experts say IPv4 addresses could run out as early as this December but will certainly be gone by the end of 2011.

ARIN and other Internet policymakers are urging website operators to deploy IPv6 by January 1, 2012, or risk disenfranchising users with IPv6 addresses by providing them with slower, less-reliable service. Among the site operators that have been leaders in offering IPv6 content are Google, Comcast, Netflix and Facebook.  Now Cisco is joining this IPv6 crowd, but has yet to publicise it.

Cisco's disclosure of its IPv6 testing efforts came on the same day that the Obama Administration held its first ever event focused on the IPv6 issues. Cisco says it is being prudent by taking a careful, testing-based approach to IPv6 deployment on its website.

"IP addresses are used by applications in a variety of ways, and only by exercising the code can we find them all," Townsley says. "The Internet is in a transition phase, and while pressure is on due to the looming IPv4 free pool run-out in 2011, we still have some time left to see how the network and applications respond, monitor traffic, and get ready for the day when we really turn the traffic up by offering an IPv6 address to the website when someone types in"

Townsley said Cisco is experiencing a very small amount of IPv6 traffic. "We want to run in alpha test mode for a while to work out any bugs in the server applications and monitor the situation. This is the good thing about starting now, as we can afford to stage the bring up and watch it carefully," he adds.

The IPv6 development and testing process that Cisco is engaged in now will be more common next year, as pressure mounts for website operators such as federal agencies to support IPv6 on their public-facing websites. Other industry laggards on IPv6 include Yahoo and Twitter.