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22.1 DNS Terminology
- Zone
-
The domain namespace is divided into regions called zones. For
instance, if you have example.com, you have the
example section, or zone, of the
com domain.
- DNS server
-
The DNS server is a server that maintains the name and IP information
for a domain. You can have a primary DNS server for master zone, a
secondary server for slave zone, or a slave server without any zones
for caching.
- Master zone DNS server
-
The master zone includes all hosts from your network and a DNS
server master zone stores up-to-date records for all the hosts in
your domain.
- Slave zone DNS server
-
A slave zone is a copy of the master zone. The slave zone DNS
server obtains its zone data with zone transfer operations from its
master server. The slave zone DNS server responds authoritatively
for the zone as long as it has valid (not expired) zone data. If
the slave cannot obtain a new copy of the zone data, it stops
responding for the zone.
- Forwarder
-
Forwarders are DNS servers to which your DNS server should send
queries it cannot answer. To enable different configuration sources in
one configuration, netconfig is used (see also
man 8 netconfig).
- Record
-
The record is information about name and IP address. Supported records
and their syntax are described in BIND documentation. Some special
records are:
- NS record
-
An NS record tells name servers which machines are in charge of a
given domain zone.
- MX record
-
The MX (mail exchange) records describe the machines to contact for
directing mail across the Internet.
- SOA record
-
SOA (Start of Authority) record is the first record in a zone file.
The SOA record is used when using DNS to synchronize data between
multiple computers.
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