Explanation/Reference:
Locking Cluster Management Interfaces (BUI)
After initial configuration, clustered controllers are in an active-active state. When a failover occurs, an active controller takes over all non-private interfaces, and the peer controller becomes passive and inaccessible by its BUI and CLI. To maintain access to a controller regardless of its state, lock its management interface to make it private. The following procedure locks the management interface on each clustered controller.
1. In the BUI of the first controller, navigate to Configuration > Cluster.
2. In the BUI of the second controller, navigate to Configuration > Cluster.
3. From the BUI of the first controller, choose the management interface for the first controller from the Resource list.
4. Click the padlock icon image:unlock icon to lock the management interface to this controller.
5. The interface displays a locked icon image:locked icon next to its name in the Resource list.
6. From the BUI of the second controller, choose the management interface for the second controller from the Resource list.
7. Click the padlock icon image:unlock icon to lock the management interface to this controller.
8. The interface displays a locked icon image:locked icon next to its name in the Resource list.
References: https://docs.oracle.com/cd/E76475_01/html/E76483/gpkay.html