Windows keep advertising wrong IP to resolve and whatever I do is not working.

all I want to do is adding a second active directory server so if one is off second of can keep the system running.

I'm a student. practicing what I have learned and maybe adding more. I know how to create a domain how to add a user to domain

For next step I am trying to add second domain controller but windows keep advertising 2 IP address of server. (one is NAT other is isolated. I want it to stop NAT IP to advertise)

what I did to disable that?

– network connections > Second NIC IPv4> Properties > Advance > DNS > (UNTICK) Registrar this connection's address in DNS

– DNS Manager > Domain Name > Properties > Interfaces > (UNTICK) Second NIC IP
I restart the dns service, clean the cache but still same. I can't see Second NIC IP in DNS Manager but when I run "resolve-dnsname domainname -Server source-IP" Second NIC IP still showing up. but it's not showing up at "nslookup domainname source-IP"

so yea. why is that?
I'm using Ubuntu as OS and VMM to virtualize the machines btw