This article was previously published under Q170998
This article has been archived. It is offered "as is" and will no longer be updated.
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 useMicrosoft Networking functionality to connect to another Windows NT-basedor Windows 95/98-based computer on the Internet. This may occur eventhough you may have been able to in the past.
A number of ISPs have disabled User Datagram Protocol (UDP) ports 137 and138 and Transmission Control Protocol (TCP) port 139 on their routers toreduce network traffic and provide protection against out-of-band (OOB)data attacks on servers. Microsoft Networking components rely on theseports (especially TCP port 139) for NetBIOS communication.
If you could previously use Microsoft Networking components over theInternet but no longer can, contact your ISP to determine if UDP ports 137or 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 Internetis not a secure configuration and is not recommended by Microsoft.However, you can use the Point-to-Point Tunneling Protocol (PPTP) as analternative method for communicating with your network over the Internet.PPTP is a networking technology that supports multiprotocol virtualprivate networks (VPNs), enabling remote users to access corporatenetworks securely across the Internet. Using PPTP, remote users can useWindows NT Workstation, Windows 95/98, and other point-to-point protocol(PPP)-enabled computers to dial into a local Internet service provider toconnect securely to their corporate networks using the Internet.
For more information about TCP ports, see the following RFC:
RFC-1700: Internet Assigned Numbers
For additional information about PPTP, see the following articles in theMicrosoft Knowledge Base:
161410 How to Set Up a Private Network Over the Internet Using PPTP