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Microsoft KB Archive/103444

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Knowledge Base

RAS Server 64 Port Limitation Information

Article ID: 103444

Article Last Modified on 10/31/2006


  • Microsoft Windows NT Advanced Server 3.1

This article was previously published under Q103444

Remote Access Service (RAS) for Windows NT Advanced Server does NOT prevent administrators from configuring more than 64 dial-in ports. However, the system will not support more than 64 simultaneous incoming connections. Attempting to do this results in unpredictable behavior. Microsoft does not support any attempt to exceed 64 simultaneous configured ports.


RAS requires that a NetBIOS LANA number be assigned for each dial-in and each dial-out port. If a port is configured for both, it requires two LANAs. Port types are assigned in the Network Control Panel application RAS Configuration screen.

   Port type                # of LANAs
   Dial-in                      1
   Dial-out                     1
   Dial-in and Dial-out         2

Windows NT has a fixed limit of 72 total NetBIOS LANAs. You should configure all your RAS ports to consume less than 64 LANAs (see the above chart). The remaining eight LANAs are generally set aside for use with other network protocol bindings.

This explains why when you look at the NetBIOS configuration in the Network Control Panel application, you will sometimes see RAS taking up more LANAs than there are COM ports installed. For example, if you have a Windows NT Advanced Server with two internal COM ports and you have configured both ports for dial-in and one port for both dial-in and dial-out, when you look at the NetBIOS configuration, you will see three LANAs assigned to RAS bindings.

For more information, query on the following word in the Microsoft Knowledge Base:


Additional query words: prodnt

Keywords: kbnetwork KB103444