Chapter 16. Berkeley Internet Name Domain (BIND)

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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:

I

last IP digit

IN

PTR

I

FQDN of system

I

I

The

last IP digit relates to the last number in an IP address that should point to a particular

I

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