What is your domain name, IP address, and nameserver names that we are working with? Are you running the nameserver yourself? I would like to see if:
1) The root nameservers resolve your domainname to your nameserver;
2) How does your name server resolve the query for your domain name;
Number 2, you are still not clear as to how you are hosting your site? Is Iplanet hosting your site, or the DNS, or what? Which web server (software) are you running?
I assume you have registered the domain name and pointed the domain to your name server? What nameserver software are you running? Did you make the DNS entries yourself? Please copy the zone file and post it here so we can see what is going on with that.
Do you have static IP addresses assigned to you?
You'll need to answer all these questions in order for me to help you.
In thinking through this I really don't see how you are going to put your webserver on an internal IP address. Usually you put it outside the firewall, and then link the site to internal resources through the webserver, not DNS. DNS just points to the public (external) resources. What is the public resource that the root nameservers point to?