In order to use the "optional server" function in the Reverse DNS Lookup tool, you must only use nameservers that refer. The tool is essentially a "Top Down" tool. The tool cannot have the last nameserver in the chain or it will generates an error.

If you want to look up your reverse DNS on a specific machine you would have to use the regular DNS Lookup tool.  You must reverse the address by hand and add in-addr.arpa to the end of the reversed IP address, select PTR for the record type, then type in the specific nameserver that hosts that record into the Optional Server and view box on that tool.

An example would be this:

Enter an IP (xxx.xxx.xxx.xxx) into the Reverse DNS Lookup tool and you will see something like this:

 
Reverse DNS for xxx.xxx.xxx.xxx

Location: United States [City: Bryn Mawr, Pennsylvania]

Preparation:

The  reverse DNS entry for an IP is found by reversing the IP, adding it to "in-addr.arpa", and looking up the PTR record.

So, the reverse DNS entry for xxx.xxx.xxx.xxx is found by looking up the PTR record for

xxx.xxx.xxx.xxx.in-addr.arpa.

All DNS requests start by asking the root servers, and they let us know what to do next.

See How Reverse DNS Lookups Work for more information.

How I am searching:

Asking i.root-servers.net for xxx.xxx.xxx.xxx.in-addr.arpa PTR record:  

       i.root-servers.net says to go to u.arin.net. (zone: 71.in-addr.arpa.)

Asking u.arin.net. for xxx.xxx.xxx.xxx.in-addr.arpa PTR record:  

       u.arin.net [204.61.216.50] says to go to NS7.VERIZON.NET. (zone: 185.71.in-addr.arpa.)

Asking NS7.VERIZON.NET. for xxx.xxx.xxx.xxx.in-addr.arpa PTR record:  Reports example.domain.com. [from 68.238.64.72]

Answer:

xxx.xxx.xxx.xxx PTR record: example.domain.com. [TTL 86400s] [A=xxx.xxx.xxx.xxx]

 Now you can see that the i.root-servers.net was asked first then the u.arin.net server was asked.  You could try this query again and specify a.root-servers.net or v.arin.net and you will see the search run from that server down to the VERIZON servers, but you can NOT put the VERIZON server into the tool since this tool looks for referral’s.

 If you want to test the NS7.VERIZON.NET machine you must go to the regular DNS Lookup tool and type in:

xxx.xxx.xxx.xxx.in-addr.arpa   then select PTR from the Select a record type, then type in NS7.VERIZON.NET (can be lower case) and you will see that the record exists on that machine.