Windows 2012 R2 License Server and Firewall Ports

Hi,

I have setup a Windows Server 2012 R2 as a RDS license server, and I have installed the necessary CALS.  This server is on the domain and in AD.  We have a separate VLAN that is isolated but can join domain for authentication purposes only, but it is behind a firewall.  What ports do I need to open on the firewall in order for the Windows 2012 Servers to aquire a license from the 2012 R2 server in the domain?

Thanks,

Mike