Err Msg: Error Connecting to <Servername> The RPC Service Is Not Available

ID: Q224460

The information in this article applies to:
IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the "Restoring the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key" Help topic in Regedt32.exe.

SYMPTOMS

When you attempt to remotely administer a multihomed IIS 4.0 computer from the Microsoft Management Console (MMC) on a local computer, the following error messages may occur:

Error connecting to <servername> The RPC service is not available
When you click OK, you may see a few additional errors similar to the following:
Unable to administer IIS "unable to connect to target machine"


CAUSE

This problem only occurs when you are trying to remotely administer a multihomed IIS 4.0 computer from the MMC on a local computer. The MMC uses the default DCOM protocol for remote communications. By default, DCOM uses the ncadg_ip_udp DCOM protocol for connections instead of ncacn_ip_tcp. Due to a problem with the ncadg_ip_udp DCOM protocol in Windows NT Service Pack 3, if the destination IIS computer is multihomed, ncadg_ip_udp causes the binding IP address to become corrupted.


RESOLUTION

To resolve this problem, obtain the latest service pack for Windows NT version 4.0. For additional information, please see the following article(s) in the Microsoft Knowledge Base:

Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack


WORKAROUND

If you have not yet implemented Windows NT Service Pack 4 in your environment, you can edit the registry to change the DCOM protocols that are used.

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).
Follow these steps exactly on the multihomed remote Web server:

  1. Back up the following registry key using Regedt32.exe (not Regedit.exe):
    HKEY_Local_Machine\Software\Microsoft\RPC
    To do this, highlight the RPC key and choose Registry, and the choose Save Key.


  2. In the RPC key, edit the DCOM Protocols setting by double-clicking on it. Change the values to reflect a different order by removing the ncadg_ip_udp protocol and moving ncacn_ip_tcp to the top of the list. Here is what it will look like before and after the change:

    Before
    ncadg_ip_udp
    ncadg_ipx
    ncacn_ip_tcp
    ncacn_spx
    ncacn_nb_nb
    ncacn_nb_ipx
    Remove ncadg_ip_udp and move ncacn_ip_tcp to the top of the list.

    After
    ncacn_ip_tcp
    ncadg_ipx
    ncacn_spx
    ncacn_nb_nb
    ncacn_nb_ipx

  3. After the changes are made, close Registry Editor and restart the computer.


STATUS

Microsoft has confirmed this to be a problem in Windows NT version 4.0. This problem was first corrected in Windows NT 4.0 Service Pack 4.


MORE INFORMATION

More technical explanations for this article are published in the following Knowledge Base article:

Q185012 COM Causes Delay on Multi-homed Computers
Below is an example of how the binding fails.

Note: Binding Vector[4] has the incorrect IP addresses in the binding handle. In this example, it combines both IP addresses from both NICs, thus corrupting the IP address format, and the connection fails.

Display STRING representation for each binding handle in Binding Vector
Binding Handle Count: 7
Binding Vector[0]: ncacn_np:\\\\ServerName[\\pipe\\000000B4.001]
Binding Vector[1]: ncalrpc:ServerName[WMSG000000B4.00000001]
Binding Vector[2]: ncacn_ip_tcp:157.61.239.61[1038]
Binding Vector[3]: ncacn_ip_tcp:157.61.239.5[1038]
Binding Vector[4]: ncadg_ip_udp:157.61.239.61157.61.239.5[1039]
Binding Vector[5]: ncadg_ip_udp:157.61.239.5[1039]
Binding Vector[6]: ncacn_nb_tcp:ServerName[106]
If you use network sniffers, such as Network Monitor, you can see the incorrect IP addresses as in the above example for Binding Vector[4].

Additional query words: mmc, ntop, iis, dcom, rpc, multi-homed, multi, homed sp hot fix qfe 


Keywords          : NT4SP4Fix 
Version           : winnt:4.0
Platform          : winnt 
Issue type        : kbbug

Last Reviewed: April 13, 1999