"The network BIOS command limit has been reached" error message in Windows Server 2003, in Windows XP, and in Windows 2000 Server (810886)

Important This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry

CAUSE

This issue may occur if the following conditions are true:

This issue may occur if the client computer submits simultaneous, long-term requests against a file server that uses the Server Message Block (SMB) protocol. An example of a long-term request is when a client computer uses the FindFirstChangeNotification function to monitor a server share for changes.
This issue may occur if the MaxCmds registry value setting on the client is less than 50, or the MaxMpxCt registry value setting on the server is less than 50.

Note The MaxMpxCt registry value setting may have a different name on other SMB/CIFS implementations. The Common Internet File System (CIFS) specification refers to it as MaxMpxCount.

RESOLUTION

Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

To resolve this issue, verify that the MaxCmds and MaxMpxCt registry values are set to 50 or more. To do this, follow these steps:

Click Start, click Run, type regedit, and then click OK.
Locate and then click the following key in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\lanmanworkstation\parameters
In the right pane, double-click the MaxCmds value.
In the Value data box, verify that the value is 50 or more.

Note In a Microsoft Windows Terminal Services environment, you may have to set the MaxCmds registry value to 500 or more. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
232476 Terminal Server client connections and logon limited by MaxWorkItem and MaxMpxCt values
Locate and then click the following key in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\lanmanserver\parameters
Note Make sure that you make this change to the lanmanserver\parameters registry key and not to the lanmanworkstation\parameters registry key mentioned in step 2.
In the right-pane, double-click the MaxMpxCt value.

Note On SMB servers that are running a version of Windows earlier than Windows 2000, the MaxMpxCt registry entry is named MaxMpxCount, but has the same function.
In the Value data box, verify that the value is 50 or more.

Note The MaxMpxCt value determines the maximum number of simultaneous, active requests that the server permits from an individual client.
Quit Registry Editor.

Note The MaxCmds and MaxMpxCt registry entries are REG_DWORD decimal entries. If they do not exist on your computer, you can create them as new REG_DWORD values. The range of values for these registry entries is between 0 and 65535.

MORE INFORMATION

The maximum number of simultaneous, active requests between an SMB client and the server is determined when a client/server session is negotiated. The maximum number of requests that a client supports is determined by the MaxCmds registry value. The maximum number of requests that a server supports is determined by the MaxMpxCt registry value. For a particular client and server pair, the number of simultaneous, active requests is the lesser of these two values.

To track the number of simultaneous, active requests on an SMB client, add the Current Commands counter in the SMB Redirector performance object to Performance Monitor.

REFERENCES

For more information about the MaxMpxCt and MaxCmds values in Windows 2000, click the following article number to view the article in the Microsoft Knowledge Base:

271148 MaxMpxCt and MaxCmds limits in Windows 2000

For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base:

232476 Terminal Server client connections and logon limited by MaxWorkItem and MaxMpxCt values

811005 User authentication to services such as Microsoft Exchange Server may time out on a member server

To obtain a compiled HTML help file of the CIFS/SMB specification, visit the following Microsoft Web site:

http://msdn.microsoft.com/downloads/list/windevwin.asp