Chapter 17. DNS Servers
DNS(Domain Name System), also known as a nameserver, is a network system that associates host names with their respective IP addresses. For users, this has the advantage that they can refer to machines on the network by names that are usually easier to remember than the numerical network addresses. For system administrators, using the nameserver allows them to change the IP address for a host without ever affecting the name-based queries, or to decide which machines handle these queries.
17.1. Introduction to DNS
17.1.1. Nameserver Zones
Example 17.1. A simple resource record
.). In Example 17.1, “A simple resource record”,
comdefines the top-level domain,
exampleits subdomain, and
salesthe subdomain of
example. In this case,
bobidentifies a resource record that is part of the
sales.example.comdomain. With the exception of the part furthest to the left (that is,
bob), each of these sections is called a zone and defines a specific namespace.
17.1.2. Nameserver Types
- Authoritative nameservers answer to resource records that are part of their zones only. This category includes both primary (master) and secondary (slave) nameservers.
- Recursive nameservers offer resolution services, but they are not authoritative for any zone. Answers for all resolutions are cached in a memory for a fixed period of time, which is specified by the retrieved resource record.
17.1.3. BIND as a Nameserver
named, an administration utility called
rndc, and a debugging tool called
dig. See Chapter 12, Services and Daemons for more information on how to run a service in Red Hat Enterprise Linux.