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| 6.1 |  | Implementing Module Redundancy in a Multilayer Switched Network |
| 6.1.5 |  | Implementing redundant power supplies |

To meet the need for power redundancy, Cisco has added redundant power as an option across a broad range of devices. Redundant power supplies are appropriate in situations that are considered mission critical. In systems with redundant power supplies, both power supplies must be of the same wattage. The Catalyst 6000 family switches allow mixing of AC-input and DC-input power supplies in the same chassis.

With redundancy enabled and two power supplies of equal wattage installed, the total power drawn from both supplies is at no time greater than the capability of one supply. If one supply malfunctions, the other supply can take over the entire system load. When two power supplies of equal wattage are used, each provides approximately half of the required power to the system. Load sharing and redundancy are enabled automatically. No software configuration is required.

With redundancy enabled and two power supplies of unequal wattage installed, both power supplies come online but a syslog message displays that the lower wattage power supply will be disabled. If the active power supply fails, the lower wattage power supply comes online and modules are powered down, if necessary, to accommodate the lower wattage power supply.

In a nonredundant configuration, the power available to the system is the combined power capability of both power supplies. The system powers up as many modules as the combined capacity allows. However, if one supply should fail and there is not enough power for all previously powered up modules, the system powers down some modules. These modules are marked as power-deny in the show module status field.

The configuration of the power supplies may be reconfigured from redundant to nonredundant at any time. When switching from a redundant to a nonredundant configuration both power supplies are enabled even if a lower wattage power supply is present. When switching from a nonredundant to a redundant configuration both power supplies are initially enabled and if they are of the same wattage, remain enabled. If they are of different wattage, a syslog message displays and the lower wattage supply is disabled.