"Network path not found" error message if more than 15 domain controllers host a domain root DFS (297177)

SYMPTOMS

When a client tries to gain access to a domain Distributed File System (DFS) root by using \\dfsservername\dfsroot, the client may receive one of the following error messages:

"Network path not found"

This message may appear if there are more than 15 domain controllers in the domain. The issue may occur with Microsoft Office common-file dialog boxes (such as the File Open or File Save dialog boxes).

Error on Windows NT 4.0 systems:

System error 53: 'Network path not found'

Error on Windows 2000 systems:

ERROR_BAD_NETPATH System error 53 has occurred. 'The network path was not found.' error 1231 ERROR_NETWORK_UNREACHABLE 'The network location cannot be reached.'

Additionally, if you execute the command nbtstat -c to list the NETBIOS TCP/IP cache of remote machine names and their IP addresses, the system will return results that show your cached computers with IP addresses of all zeros: 0.0.0.0.

CAUSE

Every domain controller in a domain registers an A record for itself against the domain name. This record is listed as "Same as parent" in DNS Manager. When the DFS client does not claim a UNC path, the server-name part of the UNC name is sent to NetBIOS for resolution. This behavior occurs when the DFS client does not recognize the target UNC name. For example, when you use the common file dialog boxes, Office parses and checks each element of the UNC name. When the server-name part is checked, "IPC$" is appended and the resulting UNC name, such as \\domainname.companyname.com\ipc$, is not recognized by the DFS client.

When DNS is used for resolving the server name, the query is for an A record against the domain name; the IP addresses for all domain controllers will be returned. The issue occurs because a buffer in the Lmhsvc.dll file on the client is limited to holding 15 IP addresses.

RESOLUTION

Microsoft Windows 2000

To resolve this problem, obtain the latest service pack for Windows 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

260910 How to obtain the latest Windows 2000 service pack

Note: For additional information about other aspects of this issue, click the following article number to view the article in the Microsoft Knowledge Base:

258960 More Than 15 IP addresses assigned to server causes Active Directory-related problems

Microsoft Windows NT 4.0

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that this article describes. Apply it only to systems that are experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question. The English version of this fix has the following file attributes or later:

   Date         Time   Version        Size    File name
   ----------------------------------------------------
   31-May-2002  16:28  4.0.1381.7165  12,048  Lmhsvc.dll

Note: The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.
Important This fix only doubles the number of domain DFS route domain controllers to approximately 30.

MORE INFORMATION

A network trace of the connection attempt shows a DNS query for type Host on the domain name. If the fully qualified domain name contains fewer than 16 characters, a NetBt query for the name is also issued. The DNS response will contain the IP addresses for all domain controllers.

The NetBIOS Helper service can only support 15 addresses per host. If 16 IP addresses are present, the connection does not succeed and no subsequent network traffic occurs.

For additional information about how to install Windows 2000 and Windows 2000 hotfixes at the same time, click the following article number to view the article in the Microsoft Knowledge Base:

249149 Installing Microsoft Windows 2000 and Windows 2000 hotfixes