An "Error 1721" error message occurs when you use Cluster Administrator (Cluadmin.exe)

When you use Cluster Administrator (Cluadmin.exe) to connect to a cluster, if you use a parameter other than the "." parameter (without the quotation marks), you receive the following remote procedure call (RPC) error message:

This issue occurs when the range of available IP ports that the Cluster Service uses to initiate communication through RPCs is less than 100 ports.

Additionally, some programs restrict the available port range when these programs are installed. One such program is Microsoft Message Queuing (also known as MSMQ).

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.

To resolve this issue, make a minimum of 100 ports available in the range of available ports that you define. If this issue continues to occur, make another 100 ports available. For example, the following registry entry has 100 ports available in the defined port range: Note If the following registry entries do not exist, you must manually create them.

• Ports: REG_MULTI_SZ: 5000-5099
• PortsInternetAvailable: REG_SZ: Y
• UseInternetPorts: REG_SZ: Y

To change the number of ports that are available, follow these steps:

1. Click Start, and then click Run.
2. In the Open box, type regedit, and then click OK.
3. Locate the following key:
   HKEY_LOCAL_MACHINE\ SOFTWARE\Microsoft\RPC\Internet
4. In the right pane, click Ports.
5. On the Edit menu, click Modify. Change the value to the range of ports that you want to use.
   Note This range must be larger than 100.
6. On the Registry menu, click Exit.
   Note You must restart the server computer for these changes to take effect.

You may have to make more than 100 ports available because many other services use DCOM ports in the dynamic range 1025 to 65000. The ports below 1025 are pre-defined ports. Examples of other services that use dynamic ports include the Windows DNS service, Windows Internet Naming Service (WINS), and the Microsoft SQL Server service.

For more information about how to configure RPC dynamic port allocation, click the following article number to view the article in the Microsoft Knowledge Base: