How to setup DNS Forwarding ?
The DNS forwarding facility of BIND Version 8 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. Let us suppose, that we have an internal DNS-2 in the HSZ (High Security
Zone) for the internal hosts and an external DNS-1 in the DMZ (Demilitarized Zone) for
the Internet Access. Using the forwarding feature DNS-2 is able to lookup Internet
hosts, forwarding queries to DNS-1.
Example in named.conf