In the N+1 backup mode, N power modules provide power supply, and one power module acts as a backup. If one power module fails, the redundant power module provides power supply to ensure normal operations of the switch.

In the N+N backup mode, N power modules provide power supply, and N power modules act as backups. Even if all the N primary power modules fail, the N redundant power modules can still ensure normal operations of the switch.

In the N+0 mode, N power modules provide power supply, and no redundant power module is available. If one power module fails and the total output of the other power modules is smaller than the actual power consumption of the switch, the switch cannot run normally.