Information
Authoritative name servers for an enterprise may be configured to receive requests from both external and internal clients.
External clients need to receive RRs that pertain only to public services (public web server, mail server, etc.).
Internal clients need to receive RRs pertaining to public services as well as internal hosts.
The zone information that serves the RRs on both the inside and outside of a firewall must be split into different physical files for these two types of clients (one file for external clients and one file for internal clients).
Solution
Edit the "named.conf" file.
Configure the internal and external view statements to use separate zone files.
Edit the internal and external zone files.
Configure the zone file to use RRs designated for internal or external use. The zone files must not share any RR.