This article explains the steps required to configure Global Catalog servers to use a specific port when servicing requests by MAPI clients. By default, the Name Service Provider Interface (NSPI), which is used by MAPI clients, will listen on a random port. In certain situations (clients connecting through a firewall), you may want to force the Global Catalog server (or servers) to listen on a single pre-defined port so that access to ports can be controlled or locked down on the firewall. This port can can be hard-coded by adding a registry value on the Global Catalog server. To do this, follow these steps.

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

1.	Start Registry Editor (Regedt32.exe).
2.	Locate and select the following key in the registry: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NTDS\Parameters
3.	On the Edit menu, click Add Value, and then add the following registry value: Value name: TCP/IP Port Data type: REG_DWORD Radix: click Decimal Value data: Enter the port number that you want (in decimal) NOTE: Port assignments should be in the range 1024 through 5000, in decimal.
4.	Quit Registry Editor.

Restart the Global Catalog server so that the static mapping will be read upon the initialization of the NSPI interface.

NOTE: The port number selected should not conflict with other programs, because this will prevent the interface from starting.

For more information about statically mapping ports on Exchange 2000, click the following article number to view the article in the Microsoft Knowledge Base: For more information about how MAPI clients access the Active Directory, click the following article number to view the article in the Microsoft Knowledge Base: