DNS Sample Domain Zone file

This file (pri.example.com) is the standard sample zone file used throughout 
this Chapter and has the following characteristics. NOTE: Both externally 
visible (public) services and internal hosts are defined in this file.

Two name servers are used one internal (ns1) and one external (ns2) to the 
domain
The mail service is external to the domain (provided by a third party)
FTP and WWW services are provided by the same host
There are two hosts named bill and fred
The host addresses are all in the class C private address range 192.168.0.0 (a slightly artificial case)

The Resource Records (RRs) are all defined separately and clicking on any highlighted RR type will take you to a detailed description.

$TTL	86400 ; 24 hours could have been written as 24h or 1d
; $TTL used for all RRs without explicit TTL value
$ORIGIN example.com.
@  1D  IN  SOA ns1.example.com. hostmaster.example.com. (
			      2002022401 ; serial
			      3H ; refresh
			      15 ; retry
			      1w ; expire
			      3h ; nxdomain ttl
			     )
       IN  NS     ns1.example.com. ; in the domain
       IN  NS     ns2.smokeyjoe.com. ; external to domain
       IN  MX  10 mail.another.com. ; external mail provider
; server host definitions
ns1    IN  A      192.168.0.1  ;name server definition     
www    IN  A      192.168.0.2  ;web server definition
ftp    IN  CNAME  www.example.com.  ;ftp server definition
; non server domain hosts
bill   IN  A      192.168.0.3
fred   IN  A      192.168.0.4 /span>

An alternate file including only hosts externally visible to the domain is also
provided. The CNAME Resource Record allows the 'www' host to provide additional
services - in this case an assumed FTP service. The CNAME could equally have 
been replaced with a conventional A RR:

ftp    IN  A      192.168.0.2

which is functionally identical. The associated reverse map zone file is 
provided.