DNS (Domain name system).

19.   Now lets test reverse lookup using dig -x 192.168.216.131 command.

NOTE: check for BOLD & UNDERLINED word from the output section for successful DNS configuration.
e.g.
[root@kalwa2 named]# dig -x 192.168.216.131

; <<>> DiG 9.7.3-P3-RedHat-9.7.3-8.P3.el6 <<>> -x 192.168.216.131
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 3477
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1

;; QUESTION SECTION:
;131.216.168.192.in-addr.arpa. IN PTR

;; ANSWER SECTION:
131.216.168.192.in-addr.arpa. 86400 IN PTR kalwa2.home.com.

;; AUTHORITY SECTION:
216.168.192.in-addr.arpa. 86400 IN NS kalwa2.home.com.

;; ADDITIONAL SECTION:
kalwa2.home.com. 86400 IN A 192.168.216.131

;; Query time: 0 msec
;; SERVER: 192.168.216.131#53(192.168.216.131)
;; WHEN: Tue Jun 16 09:01:06 2015
;; MSG SIZE rcvd: 105
20.  nslookup

e.g.
[root@kalwa2 named]# nslookup
> kalwa2.home.com
Server: 192.168.216.131
Address: 192.168.216.131#53

Name: kalwa2.home.com
Address: 192.168.216.131

Click next page for Video log of the DNS server configuration activity.