To set up DNS for a child domain, create a delegation record on the parent DNS server for the child DNS server. Create a secondary zone on the child DNS server that transfers the parent zone from the parent DNS server.
Note Windows Server 2003 has additional types of zones, such as Stub Zones and forest-level integrated Active Directory zones, that may be a better fit for your environment. Set the child domain controller to point to itself first. As soon as an additional domain controller is available, set the child domain controller to point to this domain controller in the child domain as its secondary.