DOCUMENT:Q224460 11-JUN-2002 [iis] TITLE :Err Msg: Error Connecting to The RPC Service... PRODUCT :Internet Information Server PROD/VER::4.0 OPER/SYS: KEYWORDS:kbWinNT400sp4fix ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Internet Information Server version 4.0 ------------------------------------------------------------------------------- IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base: Q256986 Description of the Microsoft Windows Registry 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 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: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk. 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 ================ For additional information about network connection delays, click the article number below to view the article in the Microsoft Knowledge Base: Q288886 PRB: Delayed DCOM Activation on Multihomed 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 : kbWinNT400sp4fix Technology : kbiisSearch kbiis400 Version : :4.0 Issue type : kbbug Solution Type : kbfix ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. 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