Server doesn't accept L2TP connections although it is configured to

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http://serverfault.com – I own a Windows Server 2003 VPN server which my clients connect to for accessing the local network.. I have configures the RRAS to use the RADIUS authentication and accept connections. The PPTP protocol works great and does all that is expected. But the L2TP protocol has some problems.. When I try to connect to the server it just stays on Connecting to domain.com... and after like one or two minutes it gives me Error 789... Doing a port scan it gave me that PPTP port 1723 is open but the L2TP ports 1701 and 500 are closed.. I don't have the Basic Firewall option enabled in the RRAS so the (HowTos)