Question about forwarder

[김경희]

Hello~~ 
Since I took charge of dns, our company has tried to divide dns server into
two. 

One server is going to manage internal zone(hosts information using
company¡¯s private network)  

and the other server is going to manage external zone(hosts information
located in DMZ zone etc¡¦) for protecting company¡¯s internal servers
information(ip, hostname).

 

The plan of separating DNS is following. 

1.       internal dns has only internal host information and external dns
has only DMZ host information. 

2.      external dns is configured as internal dns¡¯s forwarder. 

3.       all users set up internal dns as primary dns. 

4.       when primary dns(=internal dns) receives query about internal host
information, internal dns responses to that query directly. 

5.      otherwise, when primary dns(=internal dns) receives query about DMZ
hosts information, internal dns is supposed to forward external dns(because
external dns is  set up as forwarder) 

external dns have to search its own external zone and response to internal
dns.

 

but, external dns(=forwarder) didn¡¯t search own DMZ zone and response is
failed.

But, external dns can search remote zone(naver. Yahoo etc¡¦) well.

 

Why can¡¯t forwarder search own zone that internal dns doesn¡¯t have? 

Is forwarder only cache server? 

 

Please answer my question¡¦ . 

Have a nice day.