External DNS and Internal DNS

[ANG Choon Gei (CSC)]

Hi there!

How do I setup an internal DNS and external DNS? The internal DNS is a
secured DNS whereby only internal user is allow for query. Conversely, the
external DNS allows the internet to query. 

What if I do not have a firewall in between external dNS and internal DNS?
This means that both of my DNS are behind firewall. Can I do without
changing the firewall policy.

Please advise.

Regards
Gary Ang