One user reported encountering this issue after migrating their Veeam setup to a new server and upgrading to version 9. Initially, backups ran smoothly, but intermittently, jobs began to fail with the following error message:
Task failed. Failed to expand object App3. Error: The RPC server is unavailable. (Exception from HRESULT: 0x800706BA)Further investigation revealed that within the Veeam interface, the Hyper-V server would sometimes fail to display any virtual machines. Rescanning the Hyper-V host resulted in discovery failures, again citing the RPC server as unavailable. Interestingly, during these episodes, basic network connectivity to the Hyper-V host remained functional – pinging the host and name resolution worked without issues, and firewalls were disabled. The problem was intermittent; after some time, VMs would reappear in Veeam, and backups would resume without a hitch, only for the error to resurface later.
Event logs on the Veeam server corroborated these issues, showing DCOM errors related to communication failures with the Hyper-V host:
DCOM was unable to communicate with the computer (computer name) using any of the configured protocols; requested by PID 1054 (C:Program FilesVeeamBackup and ReplicationBackupVeeam.Backup.Manager.exe).Initial troubleshooting steps, such as verifying that RPC services were running on both the Veeam server and the Hyper-V host, disabling firewalls, and checking DNS resolution, proved inconclusive.
To effectively troubleshoot the “RPC server unavailable” error in Veeam, consider these additional steps:
- Service Status Verification: While you’ve checked RPC services, double-verify the status of related services on both the Veeam server and the Hyper-V host. Services like “RPC Endpoint Mapper”, “DCOM Server Process Launcher”, and “Remote Procedure Call (RPC)” should be running and set to automatic startup.
- Firewall and Security Software: Even with firewalls disabled, security software or Windows Firewall configurations might still interfere. Temporarily disable all security software on both servers for testing purposes to rule out interference. Ensure that if you re-enable the firewall, specific rules are in place to allow Veeam and RPC communication.
- Network Connectivity Deep Dive: Beyond basic ping and DNS resolution, investigate network connectivity more thoroughly. Use tools like
Test-NetConnection(PowerShell) to test port connectivity (port 135 and dynamic RPC ports) between the Veeam server and Hyper-V host. Network latency or packet loss can also contribute to intermittent RPC issues. - Authentication and Permissions: RPC communication relies on proper authentication. Ensure that the Veeam Backup Service account has sufficient permissions on both the Veeam server and the Hyper-V host. Check for any recent changes to domain policies or user account settings that might have affected permissions.
- Time Synchronization: Time discrepancies between the Veeam server and the Hyper-V host can sometimes cause RPC communication problems. Ensure that both servers are synchronized to the same time source.
- Veeam Component Issues: In rare cases, the issue might stem from corrupted Veeam components. Consider performing a repair installation of Veeam Backup & Replication on the Veeam server.
By systematically checking these areas, you can narrow down the root cause of the intermittent “RPC server unavailable” error and restore reliable Veeam backups in your environment. Remember to test any changes thoroughly and revert if necessary.
