Microsoft KB Archive/170998

= Cannot Log in to Windows NT Domain Over Internet Connection =

Article ID: 170998

Article Last Modified on 1/20/2007

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APPLIES TO


 * Microsoft Windows 95
 * Microsoft Windows 98 Standard Edition
 * Microsoft Windows NT Server 3.51
 * Microsoft Windows NT Server 4.0 Standard Edition
 * Microsoft Windows NT Workstation 3.5
 * Microsoft Windows NT Workstation 3.51
 * Microsoft Windows NT Workstation 4.0 Developer Edition

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This article was previously published under Q170998



SUMMARY
If you are connected to the Internet through an Internet service provider (ISP), you may not be able to log in to a Windows NT Domain, or use Microsoft Networking functionality to connect to another Windows NT-based or Windows 95/98-based computer on the Internet. This may occur even though you may have been able to in the past.



MORE INFORMATION
A number of ISPs have disabled User Datagram Protocol (UDP) ports 137 and 138 and Transmission Control Protocol (TCP) port 139 on their routers to reduce network traffic and provide protection against out-of-band (OOB) data attacks on servers. Microsoft Networking components rely on these ports (especially TCP port 139) for NetBIOS communication.

If you could previously use Microsoft Networking components over the Internet but no longer can, contact your ISP to determine if UDP ports 137 or 138 or TCP port 139 has been disabled on the ISP's routers.

NOTE: This method of connecting to a Windows NT domain over the Internet is not a secure configuration and is not recommended by Microsoft. However, you can use the Point-to-Point Tunneling Protocol (PPTP) as an alternative method for communicating with your network over the Internet. PPTP is a networking technology that supports multiprotocol virtual private networks (VPNs), enabling remote users to access corporate networks securely across the Internet. Using PPTP, remote users can use Windows NT Workstation, Windows 95/98, and other point-to-point protocol (PPP)-enabled computers to dial into a local Internet service provider to connect securely to their corporate networks using the Internet.

