Technical data

Configuring and Managing BIND
5.1 Key Concepts
5.1.2.1 Master Servers
A master server is the server from which all data about a domain is derived.
Master servers are authoritative, meaning they have complete information
about their domain and their responses are always accurate.
To provide central control of host name information, the master server loads
the domain’s information directly from a disk file created by the domain
administrator. When a new system is added to the network, only the database
located on the master server needs to be modified.
A master server requires a complete set of configuration files: zone, reverse
domain, configuration file, hint file, and loopback files.
5.1.2.2 Slave Servers
Slave servers receive authority and their database from the master server.
A particular domain’s database file is called a zone file and copying this file to
a slave server is called a zone file transfer. A slave server assures that it has
current information about a domain by periodically transferring the domain’s
zone file. Slave servers are also authoritative for their domain.
Configuring a slave server is similar to configuring a master server. The only
difference is that you need to provide the name of the master server from which
to transfer zone data.
Note
If you create a master, slave, or forwarder server for the same domain on
which your local host resides, you should reconfigure your BIND resolver
so that it uses this system (LOCALHOST) as its name server.
Slave servers require a configuration file, a hint file, and loopback files.
5.1.2.3 Caching-Only Servers
Caching-only servers get the answers to all name service queries from other
name servers. Once a caching server receives an answer to a query, it saves the
information and uses it in the future to answer queries itself. Most name servers
cache answers and use them in this way but a caching-only server depends on
this for all its server information. It does not keep name server database files
as other servers do. Caching-only servers are nonauthoritative, meaning that
their information is secondhand and can be incomplete.
Caching-only servers require a hint file and loopback files.
5.1.2.4 Forwarder Servers
The forwarding facility can be used to create a large sitewide cache on a few
servers, reducing traffic over links to external name servers. Forwarder servers
process requests that slave servers cannot resolve locally (for example, because
they do not have access to the Internet).
Forwarding occurs on only those queries for which the server is not authoritative
and does not have the answer in its cache.
A master or slave server specifies a particular host to which requests outside
the local zone are sent. This is a form of Internet courtesy so that only a limited
number of hosts actually communicate with the root servers listed in the file
ROOT.HINT.
Configuring and Managing BIND 5–3