Cisco Blogs

World IPv6 Day: Working Together Towards a New Internet Protocol

January 21, 2011 - 61 Comments

We’re pleased to announce that Cisco is joining The Internet Society for World IPv6 Day, a 24-hour global “test drive” of IPv6 on June 8, 2011.

For over 25 years, Cisco has been central to the development of the Internet Protocol (IP) that has helped fuel the incredible growth in global connectivity the world enjoys today. Very soon, the free pool of IPv4 addresses will finally run dry, and IPv6 is the only long-term solution the industry has available to continue growth in the manner that the world has come to expect.

Cisco has been involved in developing standards and products for IPv6 since its inception more than a decade ago. While we have helped a number of customers deploy IPv6 on networks large and small, stitching this together ubiquitously and seamlessly among not just the networks themselves but the software and applications running on top has been challenging.

On June 8, the industry is coming together to deploy and test IPv6 in what we believe will be an unprecedented manner in terms of participation and scale. On this day, major web companies, Internet Service Providers, enterprises, and equipment vendors will work together to “switch on” IPv6 for 24 hours. The switch that will be thrown is one within the global Domain Name System, or DNS, which translates a name such as into an IP address. Today, while a number of large websites have IPv6 connectivity, in order to reach many of them over IPv6 the user must use a special DNS name. For example, even if you have an IPv6-enabled device connected to an IPv6-enabled network, you must type in your web browser in order to receive an IPv6 destination address to connect to.

On World IPv6 Day, we will advertise both an IPv4 and IPv6 address in the DNS for for 24 hours along with the rest of the World IPv6 day participants. This will allow devices that have IPv6 connectivity to use it without requiring the user to type a special name, while those that do not have IPv6 will continue to reach our site as they always have over IPv4. Most major operating systems sold today have IPv6 capability built-in, but may not be configured to use IPv6 properly or may not be connected to an IPv6-enabled network. Further, those that do have IPv4 and IPv6 configured but have latent IPv6 connectivity problems can face noticeable delays due to the logic that these computers, tablets, and phones use when deciding whether to use IPv4 or IPv6. One of the very important goals of this experiment is to help the industry measure, work through, and put to rest a number of these types of issues.

In the coming months, Cisco will be working with our development teams, Cisco Services teams, and customers to ensure that this global experiment meets its objectives with the least amount of disruption possible to Internet users worldwide. We’ll be writing more soon about how World IPv6 Day might impact you, and what you can do to prepare for it.

IPv4 has served us remarkably well for the past 30 years.  Moving to a new version will not be easy, but it is essential to the continued growth of the Internet we have come to depend upon.

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  1. It's good information about IPv6. Thanks. I'm glad to see that Cisco is leading in this latest technology. But is IPv6 compatible with Windows Vista and Windows 7?

    • Yes, both Windows Vista and Windows 7 have IPv6 enabled by default. All you need is an IPv6 network to connect to.

  2. However, as with IPv4, IPv6 as the IP address can cause a lot of waste. Precisely, the use of IPv6 networks and 2 ^ 128 is not able to take full advantage of the address.

    • It is important to balance the goal of address space utilization with the goal of flexibility of administrative aggregation of prefixes and subnets. IPv4 provided greater address space utilization at the cost reduced flexibility in subnet management and segment readdressing. The very nature of IP routing leans towards sparse address space utilization. The good news is that the address space is so much bigger in IPv6 that the sparseness of address assignment will not cause the same pressures seen in IPv4.

  3. Really Great Mark Townsley, thank you very much for your information

  4. Thank you Carlos I need to read more about ipv6

  5. It will impact lots of business and homeusers if there is no transparent IPv4 to IPv6 testing and IPsec testing etc so great idea too!

  6. ISP’s have been dragging their feet over V6 for far too long and this I worry might be too little too late. We’re going to run out of v4 addresses long before v6 is widely adopted and I think we all know this.

  7. IPv6, a new version of IP, supports a much larger address space and helps to enable new types of applications for communication and collaboration.

  8. To help prepare for World IPv6 Day, we have launched a "World IPv6 Day - IPv6 Transition" online Cisco Support Community as a source of knowledge for IPv6-related topics, and for you to ask questions, make comments, and create documents about IPv6 transition and World IPv6 Day. All topics are welcome, including IPv4/v6 co-existence and integration, routing, address management, translation, tunneling, Firewalling, Security, DNS, MTU, network management, troubleshooting, and protocol stack issues. Check it out at

  9. Absolutely William, I was also making the exact same point. However, Phillip make things very clear with the article, coz of which we dont have to worry about for a long time now. Good Stuff Cisco Team!! Karan Mehta

  10. It seems like we are going to run out of v4 addresses before v6 addresses are adopted. Some areas of technology are running way ahead of other areas.

  11. Good article. Congratulaions

  12. I think that we can be sure to see more web sites adopt or upgrade to IPv6,i.e. many new websites. Also new technology is already appearing that only support direct IPv6 connections (eg licensed music websites). Geo-locate is only at RiR or LIR level at the moment as they have not been assisgned so have no regions. If thats not no tunnel access enough, then direct access IPv6 systems will not work will they?

  13. Great work Cisco!!! I was wondering what happens after IPV6 addresses gets over? Is there any solution to that right now? Or something is being worked upon? Karan Mehta

    • IPv6 exhaustion is unlikely to ever be an issue; it was explicitly designed to be the last protocol ever needed for IP communication. 340 undecillion is unfathomably larger than 4 billion. Even when IPv4 was conceived in 1977, the limits were fathomable - less than 1 IP address for each human on the planet. But 340 undecillion? Picture the planet covered in cells, packed tightly together, 15 feet deep. In that scenario, each cell could have about 340 IPv6 addresses. (source:

  14. Hmm, my second inline link was mashed for some reason. Maxmind's work on IPv6 geolocation is noted here:

  15. Hmm, my inline link was masked for some reason. Comcast's IPv6 efforts are at

  16. Will it affect web sites using content geo-localization such as this car insurance web site ?

    • IP Geolocation tools will need to evolve to adapt to IPv6. See this thread for some recent discussions. Maxmind has a sample IPv6 Geolocation database here

  17. Looks like it is going to be either very expensive or not possible for lots broadband providers (ISP's) to provide IPv6 internet. These are going to be testing times as we cannot simply turn back the clock and reuse IPv4 addresses (Twitter/Buzz) and there's no restart that will put this right Microsoft. The only thing we can do is to upgrade. Although systems such as teredo and 6to4 will make tunneling possible I have used them to access various IPv6 sites, however this will not allow me to connect to the new IPv6 services which are starting the follow?

    • Actually, using the transition technologies like 6to4 will allow you to access all new IPv6 services. IPv6 is IPv6, regardless of whether you use it to access the web or any other service, as long as your personal computer has an IPv6 stack. Windows XP SP3, in fact, has a primitive IPv6 stack, but the stack is disabled by default (and easy to turn on). Windows Vista and later have a full IP stack on by default. All modern Linux and MacOS support IPv6, as do iPhones and iPads in iOS 4.0 and later and also Android devices, version 2.1 and later. ISPs are frantically working to roll out IPv6. For example, see what Comcast is doing.

  18. AMEN

  19. Same here in South-Africa. ISP's like "IS" are really dragging with migrating to IPv6. But, for growth it is a must. IPv6 is the future whether we want to accept it or not.

  20. IPv6 is very good project. I agree with all.

  21. its good that happens, IPv6 is better...

  22. Also I agree UK ISP's are dragging there feet, as the largest providers BT and Virgin Media have not enabled IPv6 and I don't think the existing technology will support it with just a flash bios upgrade lol. What is the solution here? are we going to all get new IPv6 routers? hhhhhmmmmmm?

    • It depends on the specific devices. I'm not familiar with BT, but in France was able to convert all 1.5 million existing users top IPv6 with existing devices to IPv6 using "6rd." RFC5569 describes their project. This is the way a lot of IPv4 providers are looking at rolling out IPv6. RFC5969 is the official RFC for 6rd.

  23. It will impact lots of business and homeusers if there is no transparent IPv4 to IPv6 testing and IPsec testing etc so great idea too!

  24. As I think Mark is hinting at, getting IPv4 space back is just pumps on the Titanic, buying you minor time on a sinking ship. “external facing IP’s” is how your IPv6 provision will work – everyone will have space to have public addresses. This is how the internet should be; the NAT from your domestic IPv4 firewall isn’t what protects your IPv4 hosts, it’s the firewall. You can still have firewalling without NAT.

  25. very interesting news, thank...

  26. the big trouble is .. some isp has his own IPv4 block and they dont want share their ip to anyone due to bussines reason. i hope ip v6 will be the alternative way

  27. About time, I look forward to IPv6 being rolled out.

  28. IPv6 is very good project

  29. Although im from Denmark this is actually pretty interesting

    • Denmark has taken a leadership role in IPv6 rollout. xs4all already provides native IPv6 connectivity, and if you search for "Denmark IPv6" you can see other activity in Denmark and the Netherlands.

  30. I agree with all

  31. well, i guess that is the question Miguel...

  32. ISP’s have been dragging their feet over V6 for far too long and this I worry might be too little too late. We’re going to run out of v4 addresses long before v6 is widely adopted and I think we all know this.

  33. i've heared that IPv4 has 10 days from now to be completed, with 1 million new IP every 4 houres

  34. ... Finally, the global deployment of IPv6. ISPs are ready?

  35. Been a long time coming! United Kingdom based ISPs have been dragging their feet for ages.

    • Yep, and if you ask them why, it's that "Don't worry, we have plenty of space left." Cases, the lot of them, but fitting of a new national sector hopelessly in love with itself and its own self-interests. I shall not be renewing a contract with a certain large and one-of-a-kind ISP in the UK; they've had it coming. In truth, they are afraid, and that will not get them anywhere. Check out the ISPs that actually care: AAISP is especially vocal. Cheers, Sabahattin

  36. Maybe we need to start talking to the uni's / some companies around the world and ask for some IP's back. I had to laugh at one uni that have all there printers and everything else mind you on external facing IP's

    • There are procedures for returning blocks to RIRs, and back in October last year Interop gave back a /8 (~16 million IPv4 addresses). That gave us about one month based on consumption rates at the time. It was nice of Interop to do this, but there's certainly no guarantee that other organizations will be so gratuitous. Would you?

    • As I think Mark is hinting at, getting IPv4 space back is just pumps on the Titanic, buying you minor time on a sinking ship. "external facing IP's" is how your IPv6 provision will work - everyone will have space to have public addresses. This is how the internet should be; the NAT from your domestic IPv4 firewall isn't what protects your IPv4 hosts, it's the firewall. You can still have firewalling without NAT.

  37. Ah, it causes me worries...having to make sure each of my machines is ready for this switch is nerve wracking. I've got an XP machine, a Win 7 machine, and a OS X Macbook. Plus my girlfriend has Vista! I see a lot of troubleshooting in my future...but it has to be done I suppose.

    • The good news is that Windows 7, Vista, and modern versions of MacOS X already have IPv6 built in and on by default. You can easily activate it in Windows XP, search the Internet for "IPv6 Windows XP"

  38. So, in other words, we're going to test IPv6 /after/ the IANA v4 pool is depleted. Shouldn't this have been done 5-7 years ago?

    • People have been working and testing IPv6 for years. This will be the first coordinated test of this scale though. You're right though, 5, 7, or even 10 years ago would have been a much better time to switch. There are many explanations as to why this didn't happen, including simple human nature to procrastinate until crises looms. This is all pretty much water under the bridge though. I prefer to look forward, and that requires the industry to move together... at least for the first few steps. That's what this Day is about.

  39. I cant agree more Chris. ISP's HAVE been dragging their feet!

  40. IPv6 it´s compatible with windows xp?

    • IPv6 for "out of the box" XP, it had to be installed explicitly. See: for more info from the source. Vista and Windows 7 have IPv6 by default, and generally prefer IPv6 over IPv4 if both are available.

      • Mark, OK so how can I learn on using IvP6? Companies that I go to look at for jobs are starting to ask if I use it or know how to use it. I leans some basics on IvP6, but that is it. You help would be greatly appreciated. -Ernie Gargsa

        • For a good online tutorial, with lots of details, on IPv6 check out: This has voice instructions too ! Enjoy, Ahmed

        • To get started on learning IPv6, start using it! You might want to get an IPv6 tunnel from one of the well established, free Tunnel Brokers and set up some services on your work and home network. Search for "IPv6 Tunnel Broker". Further, there is a free step by step set of exercises offered by some providers (Search: "Free IPv6 certification"). Lots of training courses available as well.

  41. Great to see cisco leading in the most important technology migration the Internet has ever faced. An important goal for this global experiment is not only to test and measure ipv6 behavior in a real life deployment, but also to build confidence for the future deployment of IPv6 in massive scale.

  42. Some very interesting news here, I am looking forward to it!

  43. I think I echo network engineers across the world when I say: about bloody time. ISP's have been dragging their feet over V6 for far too long and this I worry might be too little too late. We're going to run out of v4 addresses long before v6 is widely adopted and I think we all know this. ISPs need to be pressured, heavily, into implementing V6 *now.*. Not tomorrow, not next week, not next year. Now.

  44. For Mark Townsley I hope it goes as well as Y2K, There was a lot of concerns, but I don't think we missed a beat. Good article. Congratulaions. I hope I will be a part of it by replacing my Tiny Eagle with a viable ipv6 router.

    • Does anyone know when the networkworld website will be back up,,,, it's been dowm all AM Thanks Dave