Troubleshooting “The RPC Server is Unavailable” Error in Veeam

Experiencing intermittent issues with Veeam backups failing with the error message “The Rpc Server Is Unavailable” can be frustrating. This error, often accompanied by the code 0x800706BA, indicates a communication breakdown between Veeam Backup & Replication and the target server, typically a Hyper-V host in the scenario described. Let’s delve into troubleshooting steps to resolve this common Veeam problem.

The user initially encountered this issue after migrating their Veeam setup to a new server and upgrading to version 9. While the problem is intermittent, it frequently disrupts backup jobs. The core symptom is that Veeam loses connection to the Hyper-V host, failing to display VMs and triggering the “RPC server is unavailable” error during rescans and job executions. Event logs further point to DCOM communication failures.

Here’s a structured approach to diagnose and fix this issue:

1. Verify Basic Network Connectivity: Although ping and DNS resolution seem to be working, double-check for less obvious network hiccups.

   • Name Resolution: Ensure both the Veeam server and Hyper-V host can reliably resolve each other’s names and FQDNs. Use nslookup or Test-NetConnection (PowerShell) for thorough checks.
   • Firewall Deep Dive: While firewalls were reportedly disabled, confirm this at the OS level on both servers. Temporarily disabling Windows Firewall via services might be necessary for a definitive test, as sometimes rules can persist or other firewall solutions might be in place. Remember to re-enable it after testing.
   • Network Segmentation: If the Veeam server and Hyper-V host are on different VLANs or subnets, ensure proper routing and no restrictive network policies are interfering with RPC communication (ports 135, 445, and dynamic RPC port range).

2. RPC Service Status and Configuration: Confirm the fundamental RPC services are running, but also check their startup type and dependencies.

   • Services to Check: On both Veeam server and Hyper-V host, verify that “RPC (Remote Procedure Call)” and “RPC Locator” services are set to “Running” and their Startup type is “Automatic”.
   • Dependencies: Inspect the dependencies of these RPC services. Ensure all dependent services are also running correctly. Issues with dependent services can indirectly cause RPC failures.

3. DCOM Configuration: Distributed Component Object Model (DCOM) is crucial for RPC communication in Windows environments.

   • DCOMCNFG: Use dcomcnfg command to open Component Services. Navigate to Component Services -> Computers -> My Computer -> DCOM Config.
   • Event Log Errors: Analyze the DCOM event log errors closely. They often provide clues about specific components or permissions causing the failure. Note the specific computer names and PIDs mentioned in the error logs as they pinpoint the failing process.
   • Permissions: DCOM errors can arise from incorrect permissions. Ensure the user account under which Veeam services are running has sufficient DCOM permissions on both the Veeam server and Hyper-V host.

4. Time Synchronization: Time discrepancies between the Veeam server and Hyper-V host can lead to authentication and communication problems, including RPC errors.

   • Check Time Sync: Verify that both servers have their time synchronized with a reliable time source (e.g., NTP server or domain controller). Even slight time differences can cause issues with Kerberos authentication, which underlies RPC security.

5. Network Interface Card (NIC) Settings: In some cases, advanced NIC settings can interfere with network communication.

   • NIC Teaming/Offloading: If NIC teaming or offloading features are enabled on either server, temporarily disable them for troubleshooting purposes. Sometimes these features, while designed to enhance performance, can cause compatibility issues with certain network protocols.

6. Veeam Specific Checks:

   • Veeam Services: Ensure all Veeam services on the Veeam server are running and configured correctly. Restarting Veeam services can sometimes resolve transient issues.
   • Veeam Credentials: Double-check the credentials used by Veeam to connect to the Hyper-V host. Incorrect or expired credentials can lead to access denied errors that manifest as RPC problems.

Intermittent RPC issues are often challenging to diagnose. By systematically checking network connectivity, RPC service health, DCOM configuration, time synchronization, and Veeam specific settings, you can methodically narrow down the root cause and implement a lasting solution to the “RPC server is unavailable” error in your Veeam environment. If the problem persists, consider collecting detailed logs from both Veeam and the Hyper-V host and engaging Veeam support for further assistance.