Known issue -DNS server may not respond to a CNAME query if 2008 r2 dns server applied MS15-127 KB 3100465

Workaround: To work around this issue, run the following command from an elevated command prompt to disable the background zone loading feature on the affected DNS server:

dnscmd /Config /DsMinimumBackgroundLoadThreads 0

Note This setting prevents incoming queries from being answered until zone loading is completed. Clients should be configured to use secondary DNS servers as a fallback in this scenario.

To re-enable background zone loading, run the following command from an elevated command prompt:

dnscmd /Config /DsMinimumBackgroundLoadThreads 1