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Consider the following scenario:
Virtual private network (VPN) is enabled in Microsoft Internet Security and Acceleration (ISA) Server 2006.
Both the Point-to-Point Tunneling Protocol (PPTP) and the Layer 2 Tunneling Protocol (L2TP) are enabled for VPN connections.
The maximum number of VPN clients is set to more than 1,000.
However, in Routing and Remote Access, only 1,000 PPTP ports and 1,000 L2TP ports are open for VPN connections. In this situation, you have to manually configure the VPN ports in Routing and Remote Access.
This problem occurs because ISA Server incorrectly interprets the maximum port number from the registry.
To resolve this problem, apply the hotfix that is described in the Microsoft Knowledge Base article 945821. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
945821 Description of the ISA Server 2006 hotfix package: December 5, 2007
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.