guys, I am having DNS problem. I've added the record together. When I did nslookup hostname , it looked fine. When I did nslookup with IP, it didn't point back to the hostname. I am using webmin to add the hostname. Any Idea?

Did you create a PTR record for each host?

Are you doing an nslookup on your Internet IP? If so, you don't control that, your ISP does. No matter what you put in your zone files, they're not authoritative for your netblock (the authority hasn't been delegated to you, so no one will ever use your servers to lookup those IPs).

What is your named.conf file? Also, how did you write yours zone files?

Guys...thanks for you help. I created the PTR and increase the serial by 1. My nslookup for my own internal IP. Another question.. I was requested to change the A1(hostname) to A2(hostname)IP still the same. I have changed it. When I did nslookup A2 it worked fine. When I did nslookup(reverse) IP, it showed up A1. Is it PTR again? I have checked the PTR, it A2-->IP. Any idea?

Guys, I found that SOA didn't increase. I think this cause the problem. Even though I updated the correct information. I have manually increase SOA by 1.When I did nslookup SOA remain the same. Any idea guys

Increase the SOA, what??? The SOA should be static (it's the Statement Of Authority). You need to make sure you increment the serial number and -HUP the daemon after every change. The order of events should be like this

edit zone file (you can make as many edits as you like)
finish editing, increment the zone serial number by one
save and close file
# ps -ef|grep named (<-- find the pid of the master named process)
# kill -HUP <pid-of-named>
$ dig @your-dns-server yourdomain.tld <record type>

PS the serial number for each zone is independent of the others. If you change the forward lookup zone (yourdomain.tld) then you need to increment the serial in that zone. If you change the reverse zone (d.c.b.a.in-addr.arpa) then you need to increment the serial in that file.