In chassis clustering, the node ID is indeed used to uniquely identify each device within the cluster. This allows for individual addressing and management of devices within the cluster configuration, which is crucial for operations and maintenance.
Typically, activating changes that involve chassis clustering configuration, such as setting or changing the node ID or forming a new cluster, requires a reboot of the devices. This ensures that all configuration changes are properly applied and that the devices can synchronize their states as part of the cluster.