Internal and External DNS servers

[Robert]

Hi Guys,
   Need some help with a nameserver being authorotive for a zone
(internal), but forwarding queries on that zone to another (external)
DNS also if the query could not be satisfied.

Using BIND 8.2.1 on Sparc Solaris 2.6, GCC 8.2.1

I know this is not regular operation of bind, but its the only way we
can get around the internal/external issues.

One zone is under our control, on the internal network.
The other zone is under admisitration by another party.

We are running a private internal network, using 10.x.x.x private
addresses on the internal network.

We have a DNS server on 1.2.3.4, authorotive for the zone 'foo.com' with
aliases for private hosts.
They have a DNS server on 6.7.8.9, authorotive for the zone 'foo.com'
with aliases for real-world hosts.

What we want, is our internal clients to query our internal zone
'foo.com' to check if there are any internal hosts matching their
request, and if not, then to query the external 'foo.com' zone.

Have tried this with a few methods, first was having two DNS's, one
hosting the internal zone 'foo.com' with NO forwarders with an IP of
2.3.4.5, and having a DNS server infront of that, hosting the zone as a
'forward' zone, so the config looked like this:

options {
	...
	forward only;
	forwarders { x.x.x.x; x.x.x.x; };
};

zone 'foo.com' {
	type forward;
	forward only;
	forwarders { 2.3.4.5; 6.7.8.9; );
};


This didn't seem to work, it seems that the first NS (2.3.4.5) would
send back an answer along the lines of 'im authorotive for this domain,
i dont know about the name you queried, dont bother asking elsewhere'.

This would never query the second forwarder for the zone, it would stop
after querying the first.  Im guessing that this is infact normal
operatin, but how does one change this behavior, or am I going about
this the wrong way?

comments please!

Thanks,
Robert.