Error 1722 RPC Server Unavailable is a quite common Windows error. Often domain administrators facing this error when AD replication is not working as expected. However, this error can also appear on workstations running Windows 10 or Windows Server, without the ADDS role installed. In this article, we will show how to troubleshoot and fix RPC error 1722 in different cases.
Active Directory Domain Controller Replication Error: The RPC Server is Unavailable
In this section we’ll take a look at the basic ways to fix Active Directory replication Error 1722: The RPC server is unavailable when syncing changes between domain controllers. You can face the error both in the domain controller event logs and when trying to start or check the replication status using the repadmin tool.
For example, you want to check the current status of Active Directory domain controllers with the command:
As you can see, some domain controllers return an error “(1722) The RPC server is unavailable”. This means that some domain controllers are unable to replicate AD data (or just inactive) for a few days.
Hint. There is a similar error RPC Server is Unavailable 0x800706BA, which is usually not associated with Active Directory domain controllers, and can occur on any Windows device. This needs to be fixed in a different way.
Let’s consider the typical reasons for such an error:
- The domain controller is offline (or broken);
- Changes have been made to the network, or new Windows Defender Firewall rules have been added to block the AD replication traffic;
- Incorrect DNS configuration on domain controllers, or invalid DNS records;
- Poor network performance or high latency.
Make sure the specified domain controllers are powered on and the following Windows services are running on them:
- COM+ Event System;
- Remote Procedure Call (RPC);
- Active Directory Domain Services;
- DNS Client;
- DFS Replication;
- Intersite Messaging;
- Kerberos Key Distribution Center;
- Security Accounts Manager;
- Windows Time;
Note. Now let’s say a few words about how replication works in an Active Directory domain. Replication (Synchronization) Active Directory is a fully automated process. Each domain controller periodically writes changes that occurred on other domain controllers (replication partners) to its local AD database (ntds.dit file). This means that to make changes from dc02 to dc01, it is required that dc02 should be the replication partner of the dc01.
First of all, to verify that everything is fine with replication, you need to make sure the UNC path \\lon-dc01 (this is a problematic DC that returns error 1722 RPC server unavailable) is accessible, and the SYSVOL and NETLOGON folders are shared.
If they are not available, you need to check the permissions on the folders and check the availability of TCP 135/445 ports, maybe they are blocked by the firewall.
Now check if TCP port 135 (RPC locator) on the domain controller returning error 1722 is in the listening state. You can do this using telnet or the PowerShell Test-NetConnection cmdlet:
telnet lon-dc01 135
Test-NetConnection lon-dc01 –port 135
A common source of such problems is the incorrect DNS configuration on the DC. Check the correct DNS servers IP addresses are specified in the DC network connection settings. The primary address should be the address of another DC, and the secondary one is it’s own IP address.
Active Directory uses the dynamic range of TCP ports for replication. Windows Server 2008 R2 (and higher) uses the following port range for TCP Dynamic RPC — from 49152 to 65535.
In some cases, an AD administrator can bind (restrict) Active Directory replication traffic on a specific port. In this case, the fixed RPC port number must be configured in the domain controller registry. For example, to bind the AD replication traffic on TCP port 5000 (0x1388), you need to change the registry key on the domain controller:
[HKLM\SYSTEM\CurrentControlSet\Services\NTDS\Parameters] "TCP/IP Port"=dword:00001388
If firewalls are used on your corporate network and the replication port AD is fixed, then replication won’t work on the newly promoted DC. This happens because the DC will try to replicate with the partner over a random port from the dynamic RPC range that is blocked by the firewalls.
After you’ve fixed all problems, you can run repadmin /replsummary command again, and check if the replication was successful. We also recommend to initiate the AD replication manually and check for errors. Make sure the dcdiag /a /q command doesn’t return errors.
RPC Server is Unavailable (Error Code: 1722) on Windows 10/Windows Server
On Windows, you may receive the error “1722 The RPC server is unavailable” if the local service/app on your computer cannot communicate with the service on the remote computer.
Note. RPC is a widely used network communication protocol for exchanging data between local computers (RPC client) and remote computer (RPC server). If the RPC client is unable to connect to the RPC server, the “RPC Server Unavailable” error appears.
In this case, first of all, you need to check that the services required for the RPC protocol are running on the remote computer:
- Remote Procedure Call (RPC);
- RPC Endpoint Mapper;
- DCOM Server Process Launcher.
Open the Service management console (services.msc), and check if the specified services are in the Running state. If not, start them manually.
Also, some network applications may return error 1722 The RPC server is unavailable if TCP/IPv6 protocol is disabled on the computer.
Open the properties of your network adapter in the control panel (Win + R > ncpa.cpl), and check if Internet Protocol Version 6 (TCP/IPv6) and File and Printer Sharing for Microsoft Network are enabled.
Then clear the DNS cache with the command:
Also, RPC error 1722 can occur when you try to print a document on a remote computer with a shared network printer. In this case, you need to check if the remote computer is turned on, and the Print Spooler service is running on it. Open the services.msc console and start the Print Spooler service.