Recursive DNS enabled can cause some issues related to unintended denial of service attacks. As such, it is recommended it is disabled unless you have a very specific reason for having it enabled.
As every system is different, the general method of disabling it is as follows:
1. Open named.conf. This file is usually found in /etc/named.conf, however if you cannot find it there, try performing:
2. Under the Options settings, make sure the follow line exists; if not, add it:
3. After that, you’re all set. All that is left is to reboot your DNS server by running this command:
service named restart