Hi,
In regards to your issue, here're my suggestions:
- If you configure three forwarders in DNS server, the DNS queries are as follows:
(1) Client queries the DNS server. DNS server immediately forwards the query to its first forwarder
(2) After <forwarding_timeout> seconds, if the first forwarder didn’t reply, the DNS server queries the second forwarder
(3) After <forwarding_timeout> +1 more seconds, if the second forwarder didn’t reply, the DNS server queries the third forwarder
(4) During this time, after one of three forwarders answering the query, next time the query with this DNS suffix will be sent to this forwarder first.
- The Microsoft DNS Server support RTT. DNS server uses (RTT) to choose between name servers authoritative for the same zone. Roundtrip time is a measurement of how long a remote name server takes to respond to queries. When the name server must choose which of a group of authoritative name servers to query, it simply chooses the one with the lowest roundtrip time.
For more details, you can refer to the following links:
https://support.microsoft.com/en-us/help/2834250/net-dns-forwarders-and-conditional-forwarders-resolution-timeouts
https://social.technet.microsoft.com/Forums/windowsserver/en-US/3350e02b-86d6-473e-a653-28fe19703be7/microsoft-dns-server-and-rtt?forum=winserverNIS#:~:text=The%20Microsoft%20DNS%20Server%20uses,it%20starts%20an%20internal%20stopwatch.
-------If my answer is helpful to you, please remember to mark them as answer. Thank you!------
Regards
Gloria