Postado originalmente por
gmlinux
coloca seu servidor para responder fazendo forward para o do seu provedor, assim, quando ele souber a resposta, ele entrega, se não ele faz uma query no provedor, este executa o processo de recursão, responde ao seu servidor que repassa a resposta ao cliente.
trecho do man:
http://www.die.net/doc/linux/man/man5/named.conf.5.html
Forwarding
The forwarding facility can be used to create a large site-wide cache on a few servers, reducing traffic over links to external nameservers. It can also be used to allow queries by servers that do not have direct access to the Internet, but wish to look up exterior names anyway.
Forwarding occurs only on those queries for which the server is not authoritative and does not have the answer in its cache.
forward
This option is only meaningful if the forwarders list is not empty. A value of first the default, causes the server to query the forwarders first, and if that doesn't answer the question the server will then look for the answer itself. If only is specified, the server will only query the forwarders.
forwarders
Specifies the IP addresses to be used for forwarding. The default is the empty list (no forwarding).
Forwarding can also be configured on a per-zone basis, allowing for the global forwarding options to be overridden in a variety of ways. You can set particular zones to use different forwarders, or have different forward only/first behavior, or to not forward at all. See Sx THE ZONE STATEMENT section for more information.