Happy Eyeballs for IPv6 is not working on Windows Xp

Deepak Ambotkar · ‎09-25-2012

Hello,

Today IPv6 public DNS (2001:4860:4860::8888) was not reachable. I am running IPv4 and IPv6 in the dual stack. I could recive the Internet table and my IPv6 subnets are announced too. I could ping all of IPv4 websites but IPv6 websites won't work (DNS issue). Now my understanding about "Happy Eyeballs" is that if Ipv6 is not reachable it will fall back to Ipv4 auto. But it did not do that in my case. To make it worse it won't open the websites which are running over IPv4 either. I had both V4 & V6 DNS servers listed in "ipconfig/all" but I won't work.

Has anybody came across this issue? Any suggestions?

Thanks& Regards,

Deepak Ambotkar

Phillip Remaker · ‎10-01-2012

Happy Eyeballs is not implemented globally in the Windows XP stack. Individual applications must support the fallback function.

PING, in particular, will not fall back at all. You need to pick the preferred protocol (it is IPv6 by default) and it will only "fall back" on DNS lookup failure, not on connectivity failure.

Individual browsers like newer versions of Firefox and Chrome support a Happy-Eyeballs-like function.

Remember, Happy eyeballs works by launching simulataneous (instead of sequential) IPv4 and IPv6 connection attempts and preferring the working (or faster) one. For a program like PING, such a strategy makes no sense since ping is inherently a diagnostic tool.

Deepak Ambotkar · ‎10-01-2012

Hi Philip,

Thank you for the reply. Well this issue is happening on my device (XP), which has both IPv4 & IPv6 running. I am talking specifically about HTTP/HTTPS here. Some of the websites run only on IPv4 (e.g. hotmail) and some run on both (e.g. google). Now when IPv6 DNS is up everything works well. But when the IPv6 DNS is not reachable it won't fallback 'google' on IPv4 and everything stops working. So I have to manually disable IPv6 stack completely to get this back to normal.

Any idea?

Thanks & Regards,

Deepak Ambotkar

Phillip Remaker · ‎10-01-2012

What do you mean by "IPv6 DNS is up?"

Also, what browser. Try Chrome or Firefox for proper results. The IE series will take many seconds to fall back.

Deepak Ambotkar · ‎10-11-2012

Philip,

To answer-

What do you mean by "IPv6 DNS is up?"

Means public DNS server for IPv6 is up as mentioned in the original question.

Well I tried firefox, chrome and IE, all are giving issues in case IPv6 DNS server goes down.

Regards,

Deepak

Phillip Remaker · ‎10-22-2012

So it sounds like your situation is that

You made successful connections using lookups on the IPv6 based DNS server.
The DNS server then became unreachable.
The IPv6 sites were now unreachable as well?

Any correct cached address should still work. However, if it was a general IPv6 outage which made the DNS server unreachable, cached DNS information for the IPv6 address might remain in place until it times out of the DNS cache. In that case, the sites become unreachable for the lifetime of the stale cache.

Once the IPv6 address age out of the cache, everything should work again.

See if ipconfig /flushdns resolves the issue when it happens.

Happy Eyeballs cannot help you if the cached DNS information becomes invalid. Happy Eyeballs sets the initial preferred path. If the network fails in the meantime, you must rely on traditional DNS timeout mechanisms for recovery.

Deepak Ambotkar · ‎10-23-2012

Philip,

Thank you for the reply again.

Yes it could be a cache for an old entries causing a problem and it might need a time to flush or time out the entries. I will try to "flushdns" and try again. But when the problem happened the issue stayed for at least 2 hours and I think that is a long time to flush the DNS entries. Do you know any default timers?

Also in your initial 3 points- The 3rd point was -

The IPv4 sites were now unreachable as well? (And not IPv6) - I guess that's what you meant.

Thanks,

Deepak

Deepak Ambotkar · ‎10-23-2012

Well I tried to "ipconfig /flushdns" but that did not solve the problem.

I made my IPv6 Internet down and websites like google did not go back on IPv4.

It definately has to do something with the DNS entries (A or AAAA).

I tried the same thing with windows 7 machine and it behaved in a similar way of not working with IPv4 DNS after IPv6 Internet is lost.

The only difference with win7 was that I just had to flush the dns cache and reboot the machine and it went back to IPv4 working Internet. For an XP machine I had to uninstall IPv6 stack completely to get IPv4 back working.

-Deepak Ambotkar

Phillip Remaker · ‎10-23-2012

How, exactly, do you make your "IPv6 Internet go down?" Are you blocking all packets or routes? Can the three way TCP handshake complete? If the XP (or Win 7) device still has a valid global IPv6 default route, it should continue to try to use IPv6. However, as SYNs fail it should also eventually fall back to IPv4 without needed an uninstall or reboot, although the process of falling back can take minutes.

APNiC did some research on the topic:

ripe64.ripe.net/presentations/78-2012-04-16-ripe64.pdf

www.potaroo.net/presentations/2011-03-31-dualstack.ppt

as did RIPE

www.potaroo.net/presentations/2011-03-31-dualstack.ppt

If there is some device or proxy answering the SYNs, it may never fall back. It seems like you have a strange situation.

Deepak Ambotkar · ‎10-25-2012

I have a GW router which has both IPv4 and IPv6 (dual stack) Internet running. I just disable IPv6 to stop IPv6 Internet because it is still under a testing phase.

Well on XP we have to add a route/DNS statically so it can be a problem. I would really to set 2 different machines with XP and Win7 on dual stack again and take the IPv6 Internet down and see how much time it takes to flush out the entries without rebooting.

It is a typical LAN setup as below-

Hosts (XP or Win7)-> L2 SWITCH->FW-> ROUTER->INTERNET

They are all in dual stack.

-Deepak

Phillip Remaker · ‎10-29-2012

Why do you have to statically add routes? If the device uses SLAAC and automatially gets the address, it should automatically pick up the route information, too.

Anyway, the references provided above should be able to help understand why kind of fallback times are reasonable. Newer Operating Systems and newer browsers are much more robust in the face of different IPv6 failures.