DNS Sample Reverse MAP Zone File

This file (192.168.0.rev) is the sample reverse map zone file used throughout this Chapter and has the following characteristics.

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

The Resource Records are all defined separately.

$TTL	86400 ; 24 hours, could have been written as 24h or 1d
$ORIGIN 0.168.192.IN-ADDR.ARPA.
@  1D  IN	 SOA ns1.example.com.	hostmaster.example.com. (
			      2002022401 ; serial
			      3H ; refresh
			      15 ; retry
			      1w ; expire
			      3h ; minimum
			     )
; Name servers for the zone - both out-of-zone - no A RRs required
       IN  NS ns1.example.com.
       IN  NS ns2.smokeyjoe.com.
; server host definitions
1      IN  PTR    ns1.example.com.
2      IN  PTR    www.example.com.            
; non server domain hosts
3      IN  PTR    bill.example.com.  
4      IN  PTR    fred.example.com.   

Hosts defined with CNAME Resource Records can have PTR records associated. Host ftp.example.com is CNAMEd in the forward map to host 192.168.0.2 we just happened to only map the www.example.com using a PTR RR for no very god reason. We could have added

2      IN  PTR    ftp.example.com.

if we had wanted to define both.

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