DNS Flag Day is February 1, 2019. On this day, Domain Name System (DNS) providers will stop supporting certain workarounds that enable name resolution for domains hosted on DNS servers that don't fully conform to newer Extension mechanisms for DNS (EDNS) protocol. For more information, visit dnsflagday.net.
Microsoft is committed to DNS Flag Day compliance. At this time, the DNS server role with Microsoft’s Window Server EDNS enabled may result in "Minor problems detected" on dnsflagday.net tests results. Intermediate devices, (such as routers, switches, etc.) may also result in compliance failures.
Domains that test as "Minor problems detected" should not be affected on DNS Flag Day and should continue to work on/after February 1, 2019 without additional updates. It is important to note that deltas occurring in DNS test results may be the result of the environment and/or intermediate devices. Customers should work with their intermediate device vendors to help address those issues.
We are currently evaluating solutions to resolve these minor issues and are committed to resolving EDNS compliance issues. These fixes will be released via Windows Update after DNS Flag Day.
What do I need to do?
No action is required for the DNS Server Role on DNS Flag Day. Administrators will need to install enhancements when they become available on Windows Updates. You can also look for EDNS compliance related updates in the Windows Update History Knowledge Base articles under “Improvements and fixes.”