Wednesday, July 28, 2010

An error occurred while testing the NSPI RPC endpoint.

I was getting the following error on an Exchange 2007 SP1 server when trying to run the for outlook anywhere.

ExRCA is testing the Name Service Provider Interface (NSPI) on the Exchange Mailbox server.
An error occurred while testing the NSPI RPC endpoint.
Test Steps
Attempting to ping RPC Endpoint 6004 (NSPI Proxy Interface) on server WATCEXCH.waturf.local
The attempt to ping the endpoint failed.
Tell me more about this issue and how to resolve it
Additional Details
RPC_S_SERVER_UNAVAILABLE error (0x6ba) was thrown by the RPC Runtime

The problem turned out to be Windows Server 2008 has made TCP/IPv6 the default communication protocol stack over which connections are made by clients connecting to the server that is running Microsoft Exchange. The RPCProxy component tries to connect to the DSProxy component through port 6004 over TCP/IPv6. However, the DSProxy component does not listen on the TCP/IPv6 stack, which causes connection requests from the RPCProxy component to fail.

Perform the following procedure:

1.Under Network Connections, select the network adapter, and then click Properties.

2.In the properties window, click to clear the check box for Internet Protocol Version 6 (IPv6).

Clearing this check box causes the RPCProxy component on the Client Access server to use TCP/IPv4 to talk to the DSProxy component on the Mailbox server.
3.Click Start, and then click Run.

4.Type regedit in the Open box.

5.Using Registry Editor, locate the following registry key:


6.Right-click the Parameters key, click New, and then click DWORD (32-bit) Value. For the key, add the following values:

Name: DisabledComponents


7.Restart the Client Access server.


  1. What's the difference between step 1/2 and 6?
    Looks a bit of the same to me? Im curious :)

  2. Also for more information about disabling IPv6 for RPC over HTTPS please see:

  3. I love you ! Been trying to get to the bottom of this for ages ! Cheers :)

  4. you safe my ass. thanks for article

  5. You are the man! Thanks for the help.

  6. Chris: Is this necessary on an Exchange 2010 environment? My understanding is that the IPv6 issue was fixed after exch 2007. Thanks.

  7. Champion, you're the Man. Worked for me, thank you!

  8. Does this effect Exchange 2013

  9. Great tip, helped me out, thanks Clint

  10. I used this post again today against an Exchange 2010 SP3 CU3 server and it worked :)

  11. Anyone tried this on Exchange 2013?

  12. Man you rock ! I've been pulling my hair for weeks to find what was wrong with Exchange and RPC.
    Thank you !

  13. Thanks a worked for me in Exchange 2007 sp3

  14. This blog saved my day.. helped me creating cutover migration endpoint. Thank You..