Zone Transfers

Zone transfers happen automatically once everything is configured correctly. During a zone transfer the files from one DNS are copied to another DNS and modified slightly. Usually they are sorted. In order for this to happen the secondary server must know the IP address of the master server. Once the IP address is known, the secondary server requests to files. The master server must be set to allow zone transfers to the secondary server. The secondary server compares the serial numbers and gets the master server files only if the serial number is greater the the serial number that is currently on the secondary server. Since the servers operate as user named the files in the /var/named/ directory and the directory itself need to be owned by named. The secondary server will then use these files until the amount of refresh or expire seconds marked in the file header have passed.