Vista and IPv6 = Problems?

I have been asked a lot recently if Vista works okay with IPv6. Apparently some people are hearing that Vista doesn't implement IPv6 correctly and it breaks your network, or something to that effect. The short answer is: YES! Everything in Vista works great with IPv6! We run thousands of tests per week during development to make sure that the stack works well with the rest of the OS, and that doesn't even count the huge number of partners and beta testers that are testing our code externally, as well.

We are also putting our technology to the test internally: we are running IPv6 almost everywhere on the MS corpnet.  A significant number of our employees run Windows Vista (What a concept, huh?) and while all of those are in dual stack mode (v4 and v6), we haven't seen any significant issues.  We are also testing an IPv6-only deployment internally, as well.  We also have partners that are deploying IPv6, and they have had no major issues getting IPv6 rolled out on their networks.

This success isn't my own; it is the result of literally hundreds of people working hundreds of thousands of manhours to re-engineer the TCP/IP stack to ensure that IPv6 was fully and completely integrated, and of the entire Windows Development team working to make sure IPv6 was properly integrated across the entire OS.  This was not a trivial process.

This is a great segue: its worth remember that deploying IPv6 is not trivial.  Just having IPv6 enabled isn't a big deal because most of the other devices on your network aren't going to be using v6 (except for other Windows Vista and Windows Server 2008 machines) so if you are talking to a printer or something, your machine will just use IPv4 by default.  Once you start trying to roll out IPv6 though, there is a lot to consider. There are a lot of variables, and not all of the skills you used in IPv4 transfer to IPv6.  You need to plan it out and be ready to troubleshoot some things during rollout. Maybe some of your applications are just not IPv6 capable, or your older hardware doesn’t understand what an IPv6 address is. Maybe it is a configuration error on a host or router.  There could be any number of issues that might cause problems, which is why I strongly recommend setting up an IPv6 test lab now - TODAY! - and testing your devices and applications to determine how they will work in an IPv6 network while building your v6 skills.

It can be really hard trying to pinpoint a root cause when IPv6 problems arise, particularly without being “hands-on” for troubleshooting. The Microsoft Networking Team is always talking to customers, though, and if you think you have an IPv6-specific issue, let us know! We’ll do what we can to help you figure it out.

I can tell you that a lot of people are running IPv6 with Windows Vista and a wide array of "stuff" and making it work. We are working on a set of IPv6 Best Practices that have been culled from our own lessons learned and from our partners deployments so that our customers don't have to repeat our mistakes.  Those Best Practices will be available soon.

We also provide tools like checkv4.exe to help you figure out if your code has any IPv4 calls hardcoded into it, as well as whitepapers like Manageable Transition to IPv6 using ISATAP, which is a joint whitepaper with Cisco describing how to ease the deployment of IPv6, and Enabling the Next Generation of Networking with End-to-End IPv6 which is another joint whitepaper with Juniper discussing IPv6 deployment and benefits. All of these are available from In short, we are working with lots of industry partners to simplify IPv6 deployment and make sure that all of our customers can gain the maximum value from IPv6.

Moral to the story? Get cracking on your IPv6 testing today! And, as always, let me know what you have to say. Now get back to work.

P.S. Sorry for the long break in blog posts. Thanks for all the emails of encouragement.  No, the NAT mafia didn't put out a contract on me. (That I know of) 

Comments (8)

  1. Anonymous says:


    Could you tell me some useful books for IPV6 learning?

  2. SeanSiler says:

    Well, that shouldn’t be happening! Send me an email via the email link at the top left corner of the page, and I will be happy to follow up with you and see if we can figure it out!

    Best Regards,

    Sean Siler

  3. WTF Chuck says:

    David’s comments are good (except for the gratuitous links!).  So often I see "professional" IT related magazines publish articles that are clearly nothing more than mechanisms to drive page views and garner more "interested/interesting readers" for their ad partners.

    Although much of their content is ok, CMP is one of the biggest offenders here and the practice seems to be slowly becoming more widespread.

    It is a pretty tough and continuous job to ascertain valid and unbiased sources for news.  I am saddened that I seem to be a member of a vanishingly small group of people who read in a critical way.  Everyone else takes these crap articles at face value.  This skill should be taught in elementary school!

    People looking for more information on IPv6 might find this link a good jumping off point:

  4. Anonymous says:

    Let me enlighten you a moment…

    I have used and tested Vista since Beta 1, my ultimate issue is this..

    I work for a support center, Vista with IPv4 and IPv6 active causes an "Unidentified Network"

    When IPv4 & IPv6 are disabled…the network is Identified…Once IPv4 is turned on….the network is Unidentified once again. Me and several techs belive IPv6 is causing this error…How do we prevent IPv6 from interfering with IPv4 or how do we fix the "Unidentified Network" issue?

  5. jordi says:

    People blame the most easy thing. For sysadmins that don’t did their work correctly (read learning about IPv6 and getting ready up-front), the easier thing is to blame IPv6 when something doesn’t work.

    There are many factors that may explain why this printer doesn’t work if IPv6 is enabled, and that doesn’t neccesarily mean an IPv6 problem. It may be a bad interaction of the printer driver, and again, the fault is not IPv6 is the printer driver or something else !

    The only way to know the reality is to be hands-on at the non-working scenario and know about IPv6, not just blame it !

  6. Anonymous says:

    This is the same article that appeared inNetwork World (see The article has received a lot of negative comments. I have reproduced my own comment on below:

    At Erion we have been using IPv6 for many years. This includes using Vista with IPv6 since the early betas of Vista. We have had very few problems. Non of the problems we have experienced have been related to faults in the IPv6 stack.

    The article doesn’t provide enough detail to be able to analyse the alleged problems with Vista and IPv6. However, I suspect that they are not really problems with Vista or IPv6. As another comment has observed the author is 24 orders-of-magnitude out in the difference between the number of IPv4 addresses and the number of IPv6 addresses. This does not instill confidence in the accuracy of the rest of the article.

    Regarding the printer problems, it is extremely unlikely that these are caused by IPv6. As any IT administrator knows there are many reasons why printing can go wrong. If the corruption was caused by IPv6 then it wouldn’t just affect printing, it would affect all other network services too.

    The ICMP issue described in the article does not make sense. ICMPv6 is IPv6’s version of ICMP. It carries out the functions that ICMP carries out in IPv4 plus many new functions only found in IPv6. Applications interface to ICMP (and IP) using the socket API. The way in which applications use the socket API is largely the same for IPv4 and IPv6. Not only this but the socket API is almost identical across all operating systems supporting IPv6, not just Vista. This means that ICMP errors are exposed to applications through the socket API. It is hard to understand what the author means here.

    I hope my comments above make it clear why I suspect that the conclusions drawn in the article are wrong.

    At Erion we have a lot of experience of implementing IPv6. We have found that IPv6 is reliable and stable across many platforms. Indeed, it is in widespread use around the world. We have found that problems with IPv6 are more often to do with misconfiguration of naming services, routing and transition mechanisms than anything to do with IPv6 itself. We always recommend that anyone interested in implementing IPv6 undertakes IPv6 training. For further information see and On the subject of IPv6 and Vista I gave a recent presentation at SambaXP on this subject. You can find that at

  7. Anonymous says:

    you might find a lot of ur ansewrs at the following sites:

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