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RPC Server Unavailable Error was Thrown by the RPC Runtime

Topic Last Modified: 2010-08-20

The Microsoft Exchange Best Practices Analyzer Tool issues an RPCPing to several Exchange Server endpoints to simulate the connections that are made when a Microsoft Outlook client connects to Microsoft Exchange Server 2007 Outlook Anywhere or to Microsoft Exchange Server 2003 RPC over HTTP. To connect, the client must be able to successfully connect to the HTTP endpoints of the Microsoft Exchange Information Store, the referral service of DSProxy within the Exchange System Attendant service, and to the DSProxy service within the Exchange System Attendant service over ports 6001, 6002, and 6004, respectively. If the test fails, the Exchange Remote Connectivity Analyzer generates the following error:

"RPC Server Unavailable error (1722) was thrown by the RPC Runtime"

This issue can be caused by any of the following conditions:

  • Failures in DNS name resolution
  • Missing or invalid ValidPorts key in the registry of the Internet-facing Exchange 2007 Client Access server or of the Exchange 2003 server
  • Exchange services not listening on the required endpoints
  • Firewalls blocking the required ports

To resolve this issue, do the following:

  • Troubleshoot name resolution, and verify that the server acting as the RPC proxy can correctly resolve the internal fully-qualified domain name (FQDN) of the mailbox server or of Exchange 2003.
  • Open Registry Editor on the Client Access server or on the front-end server, and verify that the ValidPorts registry value exists under HKEY_LOCAL_MACHINE\Software\Microsoft\Rpc\Rpcproxy. Also confirm that the key includes the NetBIOS and FQDN for all mailbox servers and for each required port (that is, for ports 6001, 6002, and 6004).
  • To test endpoint connectivity, open a Telnet session on the Client Access server or on the front-end server, and then Telnet to each port on the mailbox servers (that is, on ports 6001, 6002, and 6004). If you cannot successfully Telnet to any of the ports, and if there is a firewall between the servers, check your firewall configuration.
  • If you are receiving this error on port 6004, and if you are using Exchange 2007 on Windows Server 2008, make sure that you have Exchange 2007 SP1 RU4 or later installed. This is because a problem that affects IPv6 can cause DSProxy requests to fail and generate this error. For more information about this specific issue, see Microsoft Knowledge Base article, "You are prompted for your credentials three times and you receive an error message when you use the Outlook Anywhere feature to connect to an Exchange Server 2007 Service Pack 1–based server that is running Windows Server 2008".
Dd439392.note(en-us,EXCHG.80).gifNote:
Modification of the ValidPorts does not apply to Microsoft Exchange Server 2010. In Exchange 2010, the registry value is ValidPorts_Exchange. You do not have to manually modify this value. This value is created by automatic configuration in Client Access Server settings.

The Exchange Remote Connectivity Analyzer is a new tool that has limited documentation at this time. In an effort to improve the documentation for each of the errors that you might receive, we would like to solicit additional information from the community. Please use the Community Content section below to post additional information about why you failed at this point. If you require technical assistance, create a post in the appropriate Exchange TechNet forum or contact support.

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When RPC over Https is enabled, but Outlook Anywhere isn't...

Then error 0x6ba will also occur.

Example to enable Outlook Anywhere by using Exchange Management Shell:

Enable-OutlookAnywhere -Server 'Exch1' -ExternalHostname 'site.contoso.org' -DefaultAuthenticationMethod 'Basic' -SSLOffloading $false

As in http://technet.microsoft.com/en-us/library/bb123542.aspx

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Exchange 2010 SP1 & Server 2008 R2
The host file entries did the trick for us as well.
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Windows 2008 & Exchange 2007 SP3 RU2 and IP6

Hi guys,

Just to add to the IP6 problem. We will had 6004 not responding even though we are at the higest patch version.

It is worth noting that the telnet commands should return the response:

ncacn_http/1.0

If they (6001, 6002, 6004) don't then that is the place to investigate.

Hope this helps someone

Tobie

(returns to lurking)

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Exchange 2010

For Exchange 14 make sure the Mailbox Replication Service is running

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ValidPorts
Those should be 6001-6002 and 6004, not 60040 as it says in the text, right?
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Edit the host file on what? The client or the 2008 Server?
Edit the host file on what? The client or the 2008 Server?
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Simple Fix on Windows Server 2008
We had this same problem on Exchange 2007 SP1 Update Rollup 9, on Windows Server 2008.

Modifying the hosts file to add the local IP address and local hostname of the Exchange server fixed the problem for us.

#127.0.0.1 localhost
#::1 localhost
10.1.1.2 mailserver
10.1.1.2 mailserver.domain.local

http://www.gurkubondi.net/blog/2009/06/outlook-anywhere-rpc_s_server_unavailable-error-0x6ba-was-thrown-by-the-rpc-runtime/
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