This tutorial is for ADDS knowledge to understand the essential role that must be online for Domain Controller to join successfully.

In this test, DC1 is the first DC that has all FSMO Roles.
Required role is transferred to DC2 and DC2’s network is disconnected.
I will perform the test to see whether new server DC3 can be joined as Domain Controller successfully and one of the FSMO role is not available.

First, we need to check FSMO roles by logging the current DC and execute ntdsutil command:
ntdsutil Roles Connections “Connect to server %LogonServer%” Quit “Select Operation Target” “List roles for conn server” Quit Quit Quit

Transfer Role to DC2	NTDSUTIL CMD	Join New DC
Domain Naming Master	ntdsutil Roles Connections “Connect to server \\DC2” Quit “Transfer Naming Master” Quit Quit	Success
RID Master	ntdsutil Roles Connections “Connect to server \\DC2” Quit “Transfer RID Master” Quit Quit	Fail
PDC Emulator Master	ntdsutil Roles Connections “Connect to server \\DC2” Quit “Transfer PDC” Quit Quit	Success
Infrastructure Master	ntdsutil Roles Connections “Connect to server \\DC2” Quit “Transfer Infrastructure Master” Quit Quit	Success
Schema Master	ntdsutil Roles Connections “Connect to server \\DC2” Quit “Transfer Schema Master” Quit Quit	Success

Conclusion

RID Master is required for new server DC3 to join as Domain Controller successfully.