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
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.
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