A Domain Name System (DNS) Server should exist in the network for the following functions.
Internet Domain Support: If your organization has a domain name and your servers are operating as web server, SMTP (mail) server or an FTP server, you require a DNS server to respond to resolution queries from the public internet so that the users in the public internet can find and access your servers and the services configured on your servers.
Local Name Resolution: You require an internal DNS server to resolve the hostnames of systems on your LAN.
Internet Name Resolution: Whenever you are connected to internet, your workstation needs to send Internet domain name resolution queries to a DNS server. The DNS server most often used for this is the ISP's DNS servers. These are the DNS servers which are operating on the public internet.
Berkeley Internet Name Domain (BIND) as a DNS Server
BIND (Berkeley Internet Name Domain) is an implementation of the Domain Name System (DNS) protocols. The name BIND stands for "Berkeley Internet Name Domain", because the software originated in the early 1980s at the University of California at Berkeley.
BIND performs name resolution services through the /usr/sbin/named daemon. BIND also includes an administration utility called /usr/sbin/rndc.
BIND stores its configuration files in the following locations:
• /etc/named.conf — The configuration file for the named daemon.
• /var/named/ directory — The named working directory which stores zone, statistic, and cache files.