Chapter 14 Berkeley Internet Name Domain (Bind); Introduction To Dns And Bind - Red Hat LINUX 7.2 Reference Manual

Section 14.1:Introduction to DNS and BIND 223
14 Berkeley Internet Name Domain
(BIND)
Today, the Internet and almost all local networks depend upon a working and reliable Domain Name
Service (DNS), which is used to resolve names of systems into IP addresses and vice versa.
In order to facilitate DNS on your network, a nameserver is required to translate these names into the
IP addresses necessary to make the connection. In addition, a nameserver can translate IP addresses
back into a system's name, commonly called a reverse lookup.
This chapter discusses BIND, the structure of its configuration files, and how it may be locally or
remotely administered.
For BIND configuration instructions using the GUI BIND Configuration Tool, please see Official
Red Hat Linux Customization Guide. Note that, if you are using the BIND Configuration Tool, you
should not manually edit your BIND configuration files, due to the fact that any manual changes will
be overwritten by the BIND Configuration Tool.

14.1 Introduction to DNS and BIND

Systems using IP networks must know the IP address of a remote machine in order to connect to it.
However, most users prefer to use names of machines, such as hostname or a fully qualified domain
name (FQDN), to specify a system when connecting to it. In addition, many programs utilize domain
names in their configuration files when referring to a remote system, in order to allow IP addresses to
be changed without modifying the system's name, among other reasons. The service that facilitates
this is caused DNS, and it is normally implemented using centralized servers that are authoritative for
some domains and refer to other DNS servers for information they do not already know.
DNS is made possible through the use of nameserver daemons that perform the IP/name translation. A
client application will request information from the nameserver, usually connecting to it on the server's
port 53. The nameserver will attempt to resolve the FQDN based on its resolver library, which may
contain authoritative information about the host requested or cached data about that name from an
earlier query. If the nameserver does not already have the answer in its resolver library, it will turn to
other nameservers, called root nameservers, to determine which nameservers are authoritative for the
FQDN in question. Then, with that information, it will query the authoritative nameservers for that
name to determine the IP address. If performing a reverse lookup, the same procedure is used, except
the query is made with an unknown IP address rather than a name.