Fix ERROR_CLUSTER_INVALID_FUNCTION 0x1718 on Windows Server

Quick answer

Restart the Cluster service on the affected node: Restart-Service -Name ClusSvc -Force. If that doesn't stick, run cluster validation and check the cluster logs.

This error code (0X00001718) shows up when a function call inside the cluster service fails without a proper reason. You'll usually see it in the System event log or in the Failover Cluster Manager console. It can happen after a patch update, a misconfigured network adapter, or when a node loses quorum momentarily. The error is generic, so the real work is figuring out what's off.

Fix steps

1. Identify the affected node. Open Event Viewer on each server in the cluster. Look for source 'Microsoft-Windows-FailoverClustering' with event ID 1556 or 1146. The node with the error is your target.
2. Restart the Cluster service. On that node, open PowerShell as Administrator and run:

   Restart-Service -Name ClusSvc -Force

   Wait about 30 seconds, then check the service status:

   Get-Service -Name ClusSvc

   You should see 'Running'. This clears transient internal states.
3. Validate the cluster. If the error returns, run a full validation. Open Failover Cluster Manager, right-click the cluster, choose 'Validate Cluster', and pick 'Run all tests'. Let it finish. Pay attention to the 'Network' and 'Storage' sections—those fail most often.
4. Check the cluster log. Sometimes validation doesn't help. The real clues are in the cluster log. Collect it with:

   Get-ClusterLog -Destination C:\ClusterLogs

   Open the newest .log file and search for '0x1718' or 'INVALID_FUNCTION'. Look at the lines just above it—that's where the failed call happens.
5. Verify time synchronization. This is a sneaky one. If the node's clock drifts more than 5 minutes from the other nodes, cluster communication breaks. Check with w32tm /query /status and correct if needed.

If the main fix doesn't work

Try these in order:

• Reboot the node. A clean restart flushes everything. Do it during a maintenance window.
• Remove and re-add the node. If it's a persistent issue, evict the node from the cluster (Remove-ClusterNode), then add it back with Add-ClusterNode. This resets its cluster state.
• Check for third-party filter drivers. Antivirus or backup software can interfere. Disable them temporarily and see if the error goes away.

Prevention tip

Set up a weekly validation task. Use Task Scheduler to run Test-Cluster -Name YourCluster every Sunday night and email the report. That way you catch problems before they cause a 0x1718.