How would one integrate a domain in a VLAN network?

[drbx19]

E.g. I have three sites with three VLANs (Students, Staff, Finance)

1. Do I set up a forest-domain structure with independent domains or do they share one?
2. Do I have a DC at each site?
3. How do I make sure that a machine in the student VLAN at site 1 is not given the same IP address as a machine in the student VLAN at site 2 (from DHCP)?

Any help is much appreciated.

 

[drbx19]

Assuming you already have DHCP in place then you don't need to change anything DHCP doesn't need to be AD integrated.

Nah I don't the whole network is being set up from scratch.