Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine the remote procedure call (RPC) binding order in use by the Exchange Server computer:

HKEY_LOCAL_MACHINE\Software\Microsoft\Exchange\Exchange Provider\Rpc_Svr_Binding_Order

If the Exchange Server Analyzer finds the value for Rpc_Svr_Binding_Order is not set to ncacn_ip_tcp,ncacn_spx,ncacn_vns_spp, a warning is displayed.

The Rpc_Svr_Binding_Order registry entry is created when you install Exchange Server on a computer. This entry determines the protocol sequence that is used for server-to-server RPC communications.

By default, the Rpc_Svr_Binding_Order entry contains the following value data:


Additional values may be in the above string if other protocols are also installed on the Exchange Server computer.

This entry specifies the order in which Exchange Server tries network communication protocols for RPC communications with other servers. For example, because TCP/IP is specified first, Exchange Server tries to communicate with other servers using RPC over TCP/IP first, before trying RPC over other protocols.

Microsoft recommends that you not change the RPC binding order from the default value. If the default value is changed, you may encounter problems during server or service startup or with server-to-server communications.

This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore the registry if a problem occurs. For information about how to restore the registry, view the "Restore the Registry" Help topic in Regedit.exe or Regedt32.exe.

To correct this error

  1. Open a registry editor such as Regedit.exe or Regedt32.exe.

  2. Navigate to: HKLM\Software\Microsoft\Exchange\Exchange Provider

  3. In the right pane, double-click Rpc_Svr_Binding_Order.

  4. In the Value data dialog box, type ncacn_ip_tcp,ncacn_spx,ncacn_vns_spp.

  5. Click OK, and then close the registry editor.

  6. Restart all Exchange Server services, or reboot the Exchange Server computer for the change to take effect.

Before you edit the registry, and for information about how to edit the registry, see the Microsoft Knowledge Base article 256986, "Description of the Microsoft Windows Registry" (

For more information about the RPC binding order, see the Knowledge Base article 325930, "How to troubleshoot connectivity issues that are caused by RPC client protocol registry entries" (