subdomain delegation issues

[Phillip L]

Hi All.

Until recently, i've been running bind for our enterprise network, with
two single nameservers.  This has worked fine (for ever!)

My most recent experiments involve installing new bind DNS servers at each
remote office, these are interconnected with godawful slow 56k data
lines...  Each remote office also has broadband internet access...

Here's the picture.   At the top of my tree, i have :

	example.net

at each remote office, i have a dns server, with has been delegated
responsibility for it's own clients :

	office.example.net

This delegation works downwards.  Clints of example.net can ping by name,
clients of office.example.net  however...

to save bandwidth, i have configured each dns server at the remote offices
to retreive and cache dns data directly from the internet.  The net result
is that when an office.example.net client tries to ping anything above
itself in the tree..  eg..

	client.example.net or even
	client.office2.example.net

The server tries to resolve example.net from the internet root servers,
which have no idea about our internal dns system...  

I have tempoarily told all office.example.net dns configurations to
forward all requests to ns.example.net which works, but uses precious
(56k!) bandwidth.. im sure there's a better way

Comments, pointers, directions etc, appreciated!

Phillip L