How to reserve a range of ephemeral ports on a computer that is running Windows Server 2003 or Windows 2000 Server

This article describes how to reserve a range of ephemeral ports on a computer that is running Microsoft Windows Server 2003, Microsoft Windows XP Professional or Microsoft Windows 2000. In some situations, you may want to reserve a range of ports so that a program or process that requests a random port will not be assigned a port that is in the reserved range. When you reserve a range of ports, only a program or process that specifically requests a port that is in the reserved range can use the port.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

To reserve a range of ports so that only a program or process that specifically requests a port that is in the reserved range can use the port, follow these steps.

Windows Server 2003 or Windows XP Professional

1. Start Registry Editor (Regedit.exe).
2. Locate and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
3. On the Edit menu, point to New, and then click Multi-string Value.
4. Right-click the new value, click Rename, type ReservedPorts, and then press ENTER.
5. Double-click the ReservedPorts value, type the range of ports that you want to reserve, and then click OK.
   
   Note You must type the range of ports in the following format:
   xxxx-yyyy
   To specify a single port, use the same value for x and y. For example, to specify port 4000, type 4000-4000.
   
   Warning If you specify the continuous ports separately and if one port is reserved and not used, the next port is not correctly reserved, and it is used.
6. Click OK.
7. Quit Registry Editor.

Windows 2000

1. Start Registry Editor (Regedt32.exe).
2. Locate and then click the following registry key:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
3. On the Edit menu, click Add Value.
4. In the Value Name box, type ReservedPorts.
5. In the Data Type list, click REG_MULTI_SZ, and then click OK.
6. In the Multi-String Editor dialog box, type the range of ports that you want to reserve.
   
   Note You must type the range of ports in the following format: xxxx-yyyy. To specify a single port, use the same value for x and y. For example, to specify port 4000, type 4000-4000.
   
   Warning If you specify the continuous ports separately and if one port is reserved and not used, the next port is not correctly reserved, and it is used.
7. Click OK.
8. Quit Registry Editor.

Note You must restart the computer after you make these changes for the changes to take effect.