Red Hat ENTERPRISE LINUX 3 Reference Manual page 200

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When looking at how an FQDN is resolved to find the IP address that relates to a particular system,
read the name from right to left, with each level of the hierarchy divided by periods (
example, defines the top level domain for this FQDN. The name
com
, while is a sub-domain under
com sales
specific machine hostname.
Except for the hostname, each section is a called a zone, which defines a specific namespace. A
namespace controls the naming of the sub-domains to its left. While this example only contains two
sub-domains, a FQDN must contain at least one sub-domain but may include many more, depending
upon how the namespace is organized.
Zones are defined on authoritative nameservers through the use of zone files, which describe the
namespace of that zone, the mail servers to be used for a particular domain or sub-domain, and more.
Zone files are stored on primary nameservers (also called master nameservers), which are truly au-
thoritative and where changes are made to the files, and secondary nameservers (also called slave
nameservers), which receive their zone files from the primary nameservers. Any nameserver can be a
primary and secondary nameserver for different zones at the same time, and they may also be consid-
ered authoritative for multiple zones. It all depends on how the nameserver is configured.
12.1.2. Nameserver Types
There are four primary nameserver configuration types:
master — Stores original and authoritative zone records for a namespace, and answers queries
•
about the namespace from other nameservers.
slave — Answers queries from other nameservers concerning namespaces for which it is con-
•
sidered an authority. However, slave nameservers get their namespace information from master
nameservers.
caching-only — Offers name to IP resolution services but is not authoritative for any zones. An-
•
swers for all resolutions are cached in memory for a fixed period of time, which is specified by the
retrieved zone record.
forwarding — Forwards requests to a specific list of nameservers for name resolution. If none of
•
the specified nameservers can perform the resolution, the resolution fails.
A nameserver may be one or more of these types. For example, a nameserver can be a master for some
zones, a slave for others, and only offer forwarding resolutions for others.
12.1.3. BIND as a Nameserver
BIND performs name resolution services through the
cludes an administration utility called
in Section 12.4 Using
BIND stores its configuration files in the following locations:
• /etc/named.conf
directory — The
• /var/named/
files.
The next few sections review the BIND configuration files in more detail.
example
/usr/sbin/rndc
.
rndc
— The configuration file for the
named
Chapter 12. Berkeley Internet Name Domain (BIND)
. The name furthest to the left,
/usr/sbin/named
. More information about
daemon.
named
working directory which stores zone, statistic, and cache
is a sub-domain under
example
, identifies a
bob
daemon. BIND also in-
can be found
rndc
). In this
.