Replication error 1722 The RPC server is unavailable

Article
07/02/2012

Updated: March 1, 2012

Applies To: Windows Server 2000, Windows Server 2003, Windows Server 2008, Windows Server 2008 R2

This topic explains symptoms, causes and how to resolve Active Directory replication error 1722: The RPC server is unavailable.

Symptoms
Causes
Resolutions

Symptoms

This article describes the symptoms, cause and resolution for resolving Active Directory replication failing with Win32 error 1722: The RPC server is unavailable.

DCPROMO promotion of a replica DC fails to create an NTDS Settings object on the helper DC with error 1722.

Dialog Title Text:

Active Directory Domain Services Installation Wizard

Dialog Message text:

The operation failed because: Active Directory Domain Services could not create the NTDS Settings object for this Active Directory Domain Controller CN=NTDS Settings,CN=<Name of DC being promoted),CN=Servers,CN=<site name>,CN=Sites,CN=Configuration,DC=<forest root domain> on the remote AD DC <helper DC>.<domain name>.<top level domain>. Ensure the provided network credentials have sufficient permissions. "The RPC server is unavailable."

DCDIAG reports that the Active Directory Replications test has failed with error 1722: “The RPC Server is unavailable"

[Replications Check,<DC Name>] A recent replication attempt failed:
From <source DC> to <destination DC>
Naming Context: <DN path of directory partition>
The replication generated an error (1722):
The RPC server is unavailable.
The failure occurred at <date> <time>.
The last success occurred at <date> <time>.
<X> failures have occurred since the last success.
[<dc name>] DsBindWithSpnEx()failed with error 1722,
The RPC server is unavailable..
Printing RPC Extended Error Info: 
<snip>

REPADMIN.EXE reports that the last replication attempt has failed with status 1722 (0x6ba).

REPADMIN commands that commonly cite the 1722 (0x6ba) status include but are not limited to:

REPADMIN /REPLSUM
REPADMIN /SHOWREPL

REPADMIN /SHOWREPS
REPADMIN /SYNCALL

Sample output from "REPADMIN /SHOWREPS" and REPADMIN /SYNCALL depicting "The RPC server is unavailable" error is shown below:

c:\> repadmin /showreps
<site name>\<destination DC>
DC Options: <list of flags>
Site Options: (none)
DC object GUID: <NTDS settings object object GUID>
DC invocationID: <invocation ID string>
==== INBOUND NEIGHBORS ======================================
DC=<DN path for directory partition>
<site name>\<source DC via RPC
DC object GUID: <source DCs ntds settings object object guid>
Last attempt @ <date> <time> failed, result 1722 (0x6ba):The RPC server is unavailable.
<X #> consecutive failure(s).
Last success @ <date> <time>

Sample output of "REPADMIN /SYNCALL" depicting "The RPC server is unavailable" error is shown below:

C:\>repadmin /syncall
CALLBACK MESSAGE: Error contacting server <object guid of NTDS
Settings object>._msdcs.<forest root domain>.<top level domain>
(network error): 1722 (0x6ba):
The RPC server is unavailable.

The "replicate now" command in Active Directory Sites and Services returns "The RPC server is unavailable."

Right-clicking on the connection object from a source DC and choosing Replicate now fails with "The RPC server is unavailable.” The on-screen error message is shown below:

Dialog title text:

Replicate Now

Dialog message text:

The following error occurred during the attempt to synchronize naming context <DNS name of directory partition> from domain controller <source Dc host name> to domain controller <destination DC hostname>:The RPC server is unavailable. This operation will not continue. This condition may be caused by a DNS lookup problem. For information about troubleshooting common DNS lookup problems, please see the following Microsoft Web site: https://go.microsoft.com/fwlink/?LinkId=5171.

NTDS KCC, NTDS General or Microsoft-Windows-ActiveDirectory_DomainService events with the 1722 status are logged in the Directory Services log in Event Viewer.

Active Directory events that commonly cite the 1722 status include but are not limited to:

Event ID	Event Source	Event String
1125	Microsoft-Windows-ActiveDirectory_DomainService	The Active Directory Domain Services Installation Wizard (Dcpromo) was unable to establish connection with the following domain controller.
1311	NTDS KCC	The Knowledge Consistency Checker (KCC) has detected problems with the following directory partition.
1865	NTDS KCC	The Knowledge Consistency Checker (KCC) was unable to form a complete spanning tree network topology. As a result, the following list of sites cannot be reached from the local site.
1925	NTDS KCC	The attempt to establish a replication link for the following writable directory partition failed.
1960	NTDS Replication	Internal event: The following domain controller received an exception from a remote procedure call (RPC) connection. The operation may have failed.

Causes

RPC is an intermediate layer between the network transport and the application protocol. RPC itself has no special insight into failures but attempts to map lower layer protocol failures into an error at the RPC layer.

RPC error 1722 / 0x6ba / RPC_S_SERVER_UNAVAILABLE is logged when a lower layer protocol reports a connectivity failure. The common case is that the abstract TCP CONNECT operation failed. In the context of Active Directory replication, the RPC client on the destination DC was not able to successfully connect to the RPC server on the source DC. Common causes for this are:

Link local failure
DHCP failure
DNS failure
WINS failure
Routing failure (including blocked ports on firewalls)
IPSec / Network authentication failures
UDP formatted Kerberos packets are being fragmented by network infrastructure devices like routers and switches.
Resource limitations
Higher layer protocol not running
Higher layer protocol is returning this error

Resolutions

Basic Troubleshooting Steps to identify the problem:

Verify the startup value and service status is correct for the Remote Procedure Call (RPC), Remote Procedure Call (RPC) Locator and Kerberos Key Distribution Center. The operating system version will determine the correct values for the source and destination system that is logging the replication error. Use the following table to help validate the settings.

Service Name	Windows 2000	Windows Server 2003/R2	Windows Server 2008	Windows Server 2008 R2
Remote Procedure Call (RPC)	Started / Automatic	Started / Automatic	Started / Automatic	Started / Automatic
Remote Procedure Call (RPC) Locator	Started / Automatic (Domain Controllers) Not started / Manual (Member Servers)	Not started / Manual	Not started / Manual	Not started / Manual
Kerberos Key Distribution Center (KDC)	Started / Automatic (Domain Controllers) Not started / Disabled(Member Servers)	Started / Automatic (Domain Controllers) Not started / Disabled(Member Servers)	Started / Automatic (Domain Controllers) Not started / Disabled(Member Servers)	Started / Automatic (Domain Controllers) Not started / Disabled(Member Servers)

Remote Procedure Call (RPC)

Started / Automatic

Remote Procedure Call (RPC) Locator