In the Domain Name System (DNS), a name server that has authority over a given zone of authority. Master name servers provide read-only copies of their DNS database to secondary name servers.
A secondary name server must obtain and update its resource records from a master name server. The process by which these records are obtained and updated between name servers is called a zone transfer.
A master name server can itself be either a primary name server or a secondary name server. If it is a secondary name server, the master name server must obtain its own resource records from another master name server. If it is a primary name server, it contains the master copy of the resource records for its zone of authority.
When you configure zone transfers between name servers, be sure that the start of authority (SOA) record for the secondary name server is correctly configured with the name of the master name server from which it will obtain its resource records. No configuration is required with the master name server itself.