My company has a firewall. My company don't have any Domain Controller nor Windows Server device.
My boss plans to configure the firewall to let users authenticate with their corporate credential (AD) before accessing company resources. He want to build a Windows server(probably latest version OS) which act as domain controller (DC). The firewall will authenticate against the DC via Kerberos/LDAP/RADIUS protocol. My boss plans to host the server with cloud service provider.
The DC will not place in my company. Can I configure the firewall with the IP address of the DC? Does both device need to be in the same network in order to work? If no, do I need a VPN connection?