Hello. Today i find something interesting i want you to know. Maybe want of you knows the cause. At my place my pc is behind a NAT device and i get by default Teredo working. That's why if i execute ping ipv6.google.com -6 it works. The interesting thing is that if i ping ipv6.google.com it does not work. Looking at Technet if found that it's a intented behavior. The DNS Service of Windows 7 by default doesnt query AAAA entries when only has a Teredo address. I created this registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\Dnscache\Parameters\AddrConfigControl with Value 0 and after that windows queries AAAA by default. Now i can browse ipv6.google.com without any hassles. The Questin is WHY?? What relations are between the DNS Cache Service and DNS Service? Why this cange the behavior? For What AddrConfigControl is exactly inteneded for? Regards and thank you!! Ricardo Polo

Hi, Please refer this article, it explain the DNS behavior in Windows Vista, but also the same theory in Windows 7: http://technet.microsoft.com/en-us/library/bb727035.aspx “If the host has at least one IPv6 address assigned that is not a link-local or Teredo address, the DNS Client service sends a DNS query for A records and then a separate DNS query to the same DNS server for AAAA records. If an A record query times out or has an error (other than name not found), the corresponding AAAA record query is not sent” “On the Internet, computers running Windows Vista by default will typically not be configured with a global address from their ISPs or from their gateway devices. At this time, typical ISPs do not support native IPv6 connectivity and typical home routers do not support the 6to4 transition technology. If a computer running Windows Vista is located behind a network address translator (NAT), the Teredo client component will automatically configure a global Teredo address, even if it is in an inactive state. However, a computer running Windows Vista will not send AAAA record queries if it only has a Teredo address assigned.” And the registry key LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\Dnscache\Parameters\AddrConfigControl set to 0 value, this will let DNS resolving through Teredo tunnel Furthermore, this article may helpful to you better understanding DNS Cache service and DNS service: http://searchtasks.answersthatwork.com/tasklist.php?File=DNSCache Please Note: Since the website is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information. Hope that helps. Regards, Leo Huang TechNet Subscriber Support in forum. If you have any feedback on our support, please contact tngfb@microsoft.com Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Hello Leo. Thank you for the explanation. I had clear everything that you explain very good. My question was... why changing a paramter in the DNS Cache Service changes the behavior of a resolution of the DNS Service... Regads, Ricardo Polo

Hi, Windows 7 have built-in support for Teredo with an unspecified extension for symmetric NAT traversal. However, if there is only a link-local and teredo address present, these operating systems will not attempt to resolve ipv6 DNS AAAA records unless an DNS A record is present, in which case IPv4 will be used. Therefore, typically only literal IPv6 URLs will use Teredo. So we should add the registry at HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\Dnscache\Parameters, AddrConfigControl = 0, and IPv6 will work over Teredo. In another word, this will resolve Ipv6 via DNS server instead of DNS cache server. Regards, Leo Huang TechNet Subscriber Support in forum. If you have any feedback on our support, please contact tngfb@microsoft.com Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.