Servers in remote offices

Hello All I need some assistance.

I have a domain abc.local it is in one location. I want to setup a child domain accounting.abc.local at another facility. Do i need to have a VPN setup between the 2 facilites or can i just have both firewalls open between the 2 facilites.

If i do not need the VPN, how do i setup the DNS, since the networks are nat’ed.

Any suggestions?

thanks D