First, zone transfer for the secondary DNS server should be allowed in Plesk. To do it list secondary DNS server’s IP in NS records for all zones on Plesk server or add it to Access Control List (ACL). ACL is managed under Server > DNS Settings > Common ACL.

For non-Plesk secondary DNS servers:

1. Create all DNS zones on the secondary DNS server in /etc/named.conf (this file location may differ depending on OS) with slavetype. For example:zone “example.com” { type slave; file “example.com.zone”; masters { 192.168.0.1; }; }

1. Restart named service.

Now the slave DNS server will get zones information from Plesk (the master DNS server).

For Plesk secondary DNS servers:

1. switch all DNS zones on the slave DNS Plesk server to slave mode and specify the Master nameserver. This can be done underDomains > example.com > DNS Settings > Switch DNS Service Mode.
2. Add the Primary NS address using the Add Record button.