How to integrate primary Plesk DNS server with secondary Slave DNS server?
If the Slave server has Plesk installed, there is no need to install the Slave DNS Manager extension.
Perform the following steps:
Add IP of the Slave DNS in the master DNS server in Tools & Settings > DNS Template > Transfer Restrictions Template
Create the same domains in both Master and Slave Plesk servers
Warning: The same domains should exist on both master and slave Plesk servers. It prevents DNS data from getting corrupted.
Change DNS to Slave mode on Slave server side in Domains > example.com > DNS Settings > Switch to Slave
Click Add Record
Specify the IP address of the primary (master) DNS server