Reverse Dns Setup

RDNS(Reverse DNS):
Reverse DNS lookup (also known as rDNS) is a process to determine the
hostname associated with a given IP address.
Typically, the DNS is used to determine what IP address is associated
with a given hostname; so to reverse resolve a known IP address is to
lookup what the associated hostname for it. A reverse lookup is often
referred to simply as reverse resolving, or more specifically reverse
DNS lookups.
The most common uses of the reverse DNS are:
=> Anti-spam
=> Network troubleshooting
=> Avoid spammers and phishers using a forward confirmed reverse DNS etc
You can use standard UNIX / Linux utilities such as nslookup, dig or
hosts to find out reverse DNS of a given IP address.
Task: Find Reverse DNS for IP 75.126.43.235 under Linux/UNIX
$ host 75.126.43.235
Output:
237.116.43.208.in-addr.arpa domain name pointer innovationframes.com.
IP 75.126.43.235 is reverse mapped to innovationframes.com.
Task: Find Reverse DNS for IP 75.126.43.235 under Linux/UNIX/Windows
OR
dig -x IP
nslookup works under Windows and UNIX like OS's:
nslookup 208.43.116.237
Output:
nslookup 208.43.116.237
;; Got recursion not available from 202.148.202.3, trying next server
Server: 203.145.184.13
Address: 203.145.184.13#53
Non-authoritative answer:
237.116.43.208.in-addr.arpa name = gw.innovationframes.com.
Authoritative answers can be found from:
116.43.208.in-addr.arpa nameserver = ns2.arpa.global-datacenter.com.
116.43.208.in-addr.arpa nameserver = ns1.arpa.global-datacenter.com.
ns2.arpa.global-datacenter.com internet address = 67.228.255.20
ns1.arpa.global-datacenter.com internet address = 67.228.254.20
How can I setup RDNS in Linux?
#vi /etc/named.conf
Add the following entries,
zone "111.90.66.in-addr.arpa" IN {
type master;
file "/var/named/66.90.111.db";
allow-update { none; };
};

Then you will need to create a new zone file something like this.
#vi /var/named/domain.com.db
add the following lines,
$TTL 86400
@ IN SOA ns1.yourhost.com. yourcontact.emailaddress.com. (
2005021601 ; serial
28800 ; refresh
14400 ; retry
3600000 ; expire
86400 ; ttl
)
IN NS ns.yourhost.com.
50 IN PTR WhatEverYouWant.Com.
51 IN PTR WhatEverYouWant.Com.
52 IN PTR WhatEverYouWant.Com.
53 IN PTR WhatEverYouWant.Com.
54 IN PTR WhatEverYouWant.Com.
55 IN PTR WhatEverYouWant.Com.
then,
rndc reload
/etc/init.d/named restart