Installation guide

Chapter 16. Berkeley Internet Name Domain (BIND) 239
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 $ORIGIN domain is
placed after them, expanding them to server1.domain.com and server2.domain.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.domain.com names, are pointed toward machines providing the appropriate services for those
names using CNAME records.
16.2.2.4. 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 looks similar to this:
last-IP-digit IN PTR FQDN-of-system
The last-IP-digit relates to the last number in an IP address that should point to a particular
system’s FQDN.
In the follow example, IP addresses 10.0.1.20 through 10.0.1.25 are pointed to corresponding
FQDNs.
$ORIGIN 1.0.10.in-addr.arpa
$TTL 86400
@ IN SOA dns1.domain.com. hostmaster.domain.com. (
2001062501 ; serial
21600 ; refresh after 6 hours
3600 ; retry after 1 hour
604800 ; expire after 1 week
86400 ) ; minimum TTL of 1 day
IN NS dns1.domain.com.
IN NS dns2.domain.com.
20 IN PTR alice.domain.com.
21 IN PTR betty.domain.com.
22 IN PTR charlie.domain.com.
23 IN PTR doug.domain.com.
24 IN PTR ernest.domain.com.
25 IN PTR fanny.domain.com.
This zone file would be called into service with a zone statement in the /etc/named.conf file that
looks similar to this:
zone "1.0.10.in-addr.arpa" IN {
type master;
file "domain.com.rr.zone";
allow-update { none; };
};
There is very little difference between this example an a standard zone statement, except for how
the zone is named. Note that a reverse name resolution zone requires the first three blocks of the IP