Will nslookup work without configuring reverse lookup?

Question

I have empty reverse lookup entries in my active directory DNS server. But nslookup is working fine even if i give "nslookup ip_address". How can it resolve the ip_address to Some FQN without making use of reverse lookup entries. I am confused with the workin of the nslookup Can anyone explain me what is happening?

Answer 1

According to your comment you have reverse looked up an IP that is not in your own domain. In this case everything is working as expected.

Let's assume you have setup an active directory domain with the DNS domain mydomain.mycompany.com and setup all clients to use this DNS server.

Your DNS server is authoritative for mydomain.mycompany.com. So every request for this domain will be answered by your server. Every request for other domains will be forwarded to the next DNS server. If you setup a reverse lookup zone then your server will check reverse lookups if the IP is in his own range and answer them, otherwise forward the request to the next DNS server.

Your server has not setup a reverse lookup zone, so every request is forwarded to the next DNS server. So if you reverse lookup an IP of one of your own computers in mydomain.mycompany.com this will not work, but if you reverse lookup an IP from somebody else (like 173.194.69.104 for www.google.com) then the authoritative server for this IP range will answer.