With fabric fencing (such as cutting network or shared disk access rather than power), it is expected that the cluster will fence the node, and then a system administrator must manually investigate what went wrong, correct any issues found, then reboot (or restart the cluster services on) the node.

Once the node reboots and rejoins the cluster, some fabric fencing devices require an explicit command to restore the node’s access. This capability is called unfencing and is typically implemented as the fence agent’s on command.

If any cluster resource has requires set to unfencing, then that resource will not be probed or started on a node until that node has been unfenced.