samba - Jul 2019 - Ping test not resolving to secondary dns ip during AD failover test

Hi Samba Team,

I have done a classic upgrade on my Samba PDC to version 4.8.5 and have
also setup a DC member joined to the AD forest. Both DC and member DC are
running on CentOS 6.6.
I try to shutdown my first AD DC to do a failover test, everything looks
fine until when I try to do a ping test to my domain name using my Windows
7 client PC, noticed the ip address it resolved to, is my first AD DC.

I ran through DC A record verification, objectGUID CNAME record
verification and it looks fine.
Test local DNS Server and nslookup are also able to resolve correctly.

Would like to know if this behavior is normal.
Is there any settings I need to do, so that when Primary DNS address is not
reacheable, it can automatically resolve to secondary DNS address.
Appreciate for the advice.

Thanks and Regards