Red Hat LINUX 7.2 Reference Manual page 237

Section 14.2:BIND Configuration Files
IN
server1
server2
dns1
dns2
ftp
mail
mail2
www
In this example, standard directives and SOA values are used. The authoritative nameservers are
set to be dns1.domain.com and dns2.domain.com, which have A records that tie them to
10.0.1.2 and 10.0.1.3, respectively.
The email servers configured with the MX records point to server1 and server2 via CNAME
records. Since the server1 and server2 names do not end in a trailing dot (.), the $ORI-
GIN domain is placed after them, expanding them to server1.domain.com and server2.do-
main.com. Through the related A resource records, their IP addresses can be determined.
The popular FTP and Web services, available at the standard ftp.domain.com and www.do-
main.com names, are pointed toward machines providing the appropriate services for those names
using CNAME records.
Reverse Name Resolution Zone Files
A reverse name resolution zone file is used to translate an IP address in a particular namespace into a
FQDN. It looks very similar to a standard zone file, except that PTR resource records are used to link
the IP addresses to a certain system's name.
A PTR record is written in a manner similar to Figure 14–18, Sample PTR record configuration.
Figure 14–18 Sample PTR record configuration
<last-IP-digit>
The <last-IP-digit> relates to the last number in an IP address that should point to a particular
system's FQDN.
In Figure 14–19, An example of a basic reverse zone resolution file, IP addresses 10.0.1.20 through
10.0.1.25 are pointed to corresponding FQDNs.
Figure 14–19 An example of a basic reverse zone resolution file
$ORIGIN 1.0.10.in-addr.arpa
MX 20 mail2.domain.com.
IN A 10.0.1.5
IN A 10.0.1.5
IN A 10.0.1.7
IN A 10.0.1.2
IN A 10.0.1.3
IN CNAME server1
IN CNAME server1
IN CNAME server2
IN CNAME server2
IN PTR <FQDN-of-system>
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