ERROR_CLUSTER_LAST_INTERNAL_NETWORK - 5066 (0x13CA)
The cluster network is the only one configured for internal cluster communication between two or more active cluster nodes. The internal communication capability cannot be removed from the network.
Updated: Feb 21, 2026
Technical Meaning
The error code ERROR_CLUSTER_LAST_INTERNAL_NETWORK (5066, 0x13CA) indicates that the cluster network in a Windows Failover Cluster configuration is the sole network used for internal communication between active nodes. This means that removing or altering this network would disrupt the cluster's ability to function properly.
Error Details
This error typically arises when an attempt is made to modify or remove a network interface that is essential for internal cluster communication. The cluster relies on this specific network for critical operations such as node-to-node communication, resource management, and failover mechanisms.
Usage Context
This error code is relevant in scenarios where administrators are managing network configurations within a Windows Failover Cluster environment. It is particularly important to understand the implications of modifying network settings when multiple nodes depend on a single internal network for their operations.
Developer Interpretation
Developers and system administrators should be aware that this error signifies a critical dependency within the cluster's network configuration. Any changes to the network interfaces used for internal communication can have severe consequences, potentially leading to cluster downtime or failure in maintaining resource availability.
Related Errors
ERROR_CLUSTER_NOT_FOUND(1219, 0x4B3): Indicates that a required cluster resource is missing.ERROR_CLUSTER_INVALID_NODE(1225, 0x4C5): Suggests an invalid node ID or configuration.
FAQ
Q: What does the error code ERROR_CLUSTER_LAST_INTERNAL_NETWORK mean?
A: This error indicates that the network in question is the last one configured for internal cluster communication and cannot be removed without disrupting the cluster's functionality.
Q: How can I avoid this error?
A: Ensure that multiple network interfaces are available for internal communication before making any changes to the current configuration. Always back up critical configurations before performing modifications.
Summary
The ERROR_CLUSTER_LAST_INTERNAL_NETWORK (5066, 0x13CA) is a specific error code indicating a critical dependency within a Windows Failover Cluster's network configuration. Administrators and developers should exercise caution when managing internal cluster networks to prevent disruptions in cluster operations.