> I have all my public dns at my ISP. I want to configure a dns server to
> resolve names for my internal hosts. I want this internal server to
> forward all Internet dns lookups to my ISPs dns server. I know how to
> do this
> My question is with respect to the cache file on the internal dns
> server. Since my internal dns server will only be doing lookups for my
> internal hosts, I do not need the usual cache file that is comprised of
> Internet Root Servers. What should my cache file consist of?
Forwarding *all* the requests to your ISP except the ones for
internal hosts will only cause extra resolution delays, so unless you
have some special requirement that does not allow you to receive DNS
traffic, it is *much* better to keep the cache, send your off-net
queries directly to the root-servers, and cache the replies. This way,
your local named will learn about the rest of the Internet, and be able
to make direct requests to domains that it has seen before.
The usual problem with your kind of setup is that of allowing what
should be a local resolution to escape outside the Private Network.
To avoid this, you merely need to tell the local named that it is
*authoritative* for the local domain (or subdomain), and make all
your local machines point to the local named as their nameserver.
You can do this even if the ISP is declared to be authoritative, because
the local nameserver will field all requests for your domain, and only
pass on requests for *other* domains. Thus, the ISP becomes
authoritative for *outside* users, and your local named is the authority
for Private Network users.
HTH
by