Troubleshooting “RPC Server is Unavailable” Error in Veeam

Understanding the “RPC Server is Unavailable” Error

The “RPC server is unavailable” error (Error code: 0x800706BA) indicates that the Remote Procedure Call (RPC) service, crucial for communication between systems, is failing. In the context of Veeam, this typically means the Veeam Backup server is unable to communicate with the Hyper-V host or other components involved in the backup process. This communication breakdown prevents Veeam from accessing VM data, initiating backup tasks, and performing other essential operations.

This error can manifest in various ways within Veeam, such as backup job failures, inability to discover VMs on a Hyper-V host, and general unresponsiveness when interacting with the Hyper-V infrastructure through the Veeam console.

Troubleshooting Steps for Veeam RPC Server Issues

Let’s explore systematic steps to diagnose and fix the “RPC server is unavailable” error in your Veeam environment.

1. Verify RPC Services Status

The first step is to ensure that RPC-related services are running correctly on both the Veeam Backup server and the Hyper-V host.

• On both servers, check the following services:

  • Remote Procedure Call (RPC): This is the core RPC service. Ensure it is running and set to “Automatic” startup type.
  • RPC Locator: While less critical, it’s good practice to ensure this service is also running.
  • DCOM Server Process Launcher: DCOM (Distributed Component Object Model) relies on RPC. Verify this service is active.

  You can check service statuses using the Services console (services.msc) in Windows. Restarting these services on both machines can sometimes resolve temporary glitches.

2. Check Firewall Configuration

Firewalls can often block RPC communication. Even if you believe firewalls are disabled, it’s crucial to verify the configuration.

• Windows Firewall: If using Windows Firewall, ensure that exceptions are in place to allow RPC communication between the Veeam server and the Hyper-V host. Specifically, ensure the following are allowed:

  • File and Printer Sharing (RPC-EPMAP)
  • Remote Administration (RPC)
  • Remote Administration (RPC-Locator)
  • Veeam Backup & Replication ports: (Refer to Veeam documentation for specific port requirements for your version).

  It’s often beneficial to temporarily disable the firewall on both the Veeam server and Hyper-V host for testing purposes. If the error resolves with firewalls disabled, you know a firewall rule is the culprit and needs proper configuration. Remember to re-enable the firewall and configure necessary exceptions after testing.

3. Confirm DNS Resolution and Network Connectivity

Incorrect DNS settings or network connectivity problems can disrupt RPC communication.

• DNS Resolution: Verify that both the Veeam server and Hyper-V host can correctly resolve each other’s names. Use the ping command with both hostname and FQDN (Fully Qualified Domain Name) to test name resolution in both directions.
• Network Connectivity: Ensure basic network connectivity between the servers. Use ping to test IP address connectivity. Check for any network issues, such as network congestion, faulty cables, or misconfigured network interfaces.

4. Investigate DCOM Settings

DCOM configuration can sometimes be a source of RPC errors, especially in more complex environments.

• DCOM Configuration: Use dcomcnfg to access Component Services. Navigate to Component Services > Computers > My Computer > DCOM Config. Review the DCOM configuration for “Veeam Backup Manager” and related Veeam components. Ensure that the “Authentication Level” is set appropriately (typically “Connect” or “Default”). Incorrect DCOM permissions can hinder RPC communication.

5. Examine Event Viewer Logs

The Event Viewer on both the Veeam server and Hyper-V host is invaluable for pinpointing the root cause of RPC errors.

• System and Application Logs: Check for error messages related to DCOM, RPC, or Veeam services around the time the backup jobs fail. The event log entries, like the “DCOM was unable to communicate…” error mentioned in the original post, provide crucial clues. Correlate the timestamps in the Event Viewer with the times of backup job failures in Veeam.

6. Intermittent Issues and Timing

The intermittent nature of the error, as described in the original scenario, suggests a possible timing or resource contention issue.

• Resource Monitoring: Monitor resource utilization (CPU, Memory, Network) on both the Veeam server and Hyper-V host during backup operations. High resource usage can sometimes lead to temporary service unavailability and RPC errors.
• Scheduled Tasks/Conflicts: Check for any scheduled tasks or processes running on either server that might be conflicting with Veeam operations or consuming resources at the times when the RPC errors occur.

Conclusion

Troubleshooting “RPC server is unavailable” errors in Veeam requires a systematic approach. By verifying RPC services, firewall settings, DNS resolution, DCOM configuration, and examining Event Viewer logs, you can effectively diagnose and resolve the issue. Remember to address network connectivity and resource constraints as potential contributing factors, especially when dealing with intermittent errors. By following these steps, you can restore reliable Veeam backups and protect your virtual environment.