Hello all,
First post here, just starting to study for MCSA. I am stuck on a problem with remote desktop connection. I cannot remote desktop to the domain controller using the domain admin account. Error message:

Why do I have to add the domain administrator to the domain remote desktop users group in order to allow him to be able to remote desktop to the domain controller? Isn't the domain administrator supposed to be allowed by default? This is what I thought I had understood, and something else seems to confirm it as well:
In the system properties of the domain controller, remote tab, "select remote users", at the bottom it says: "contoso\administrator already has access".
Now it does let me add the administrator (domain admin account) to the domain remote desktop users group. And indeed if I add it, the problem is solved and I can remote desktop to the domain controller using the domain admin account. Is this normal? Am I missing something?
In RDP-Tcp properties/Permissions, I left everything to default: Contoso\Administrators has full control, Remote Desktop Users have user and guest access.
What's even harder to understand is that if I add simple users (non-admin) to the Remote desktop users group on the domain controller, those users are able to remote desktop to it. I thought that only members of the domain administrators group could remote desktop to a domain controller. So why would adding simple users to the remote desktop users group be enough for my domain controller to grant them access to remote desktop?
In administrative tools/Domain Controller Security Policy, as well as in administrative tools/Domain Security Policy, I have not changed anything to the "Allow log on through terminal services" policy. It's set to "not defined" in both cases. So I really don't see what's causing this.
Any help appreciated.
Cheers!