Hi
So we have a domain with 2012R2 DC servers all working fine with no DNS issues - DNS is AD integrated. I have built a new 2019 core DC server which seems to be working fine (no dcdiag issues). However after a while some CNAME look ups fail and only work again after I clear the DNS cache. They work fine all the time on the 2012R2 servers even when they fail on the 2019 server.
It is only CNAME entries that map to AZURE sites that fail:
mystudents.activatelearning.ac.uk -> mystudents-activatelearning.msappproxy.net.
And only when I query DNS on the 2019 server
C:\Users\adm.iharrison>nslookup mytargets.activatelearning.ac.uk 127.0.0.1
Server: localhost
Address: 127.0.0.1
*** localhost can't find mytargets.activatelearning.ac.uk: Server failed
When those nslookups fail on the 2019 server other nslookups against other sites work fine, its only the ones where a CNAME is used against an AZURE hosted site.
If I run the same nslookup query against a 2012R2 server it works fine.
I have tried everything I can think of, even rebuilt the 2019 server again with no luck.
Any ideas please
Thanks
Ian
