[Cisco Equipment and Related Hardware] How must the power to a system with dual power supplies on a Cisco Nexus switch be connected?

To achieve true power redundancy and high availability, each power supply in a dual-supply system must be connected to an independent power source. This ensures that the failure of a single power circuit, Power Distribution Unit (PDU), or utility feed does not cause the entire switch to lose power. Connecting both supplies to the same source creates a single point of failure, negating the benefit of having a second power supply. The goal is to protect against source failure, not just the failure of a single power supply unit.

A. This is one specific implementation of separate sources but is not the only way; the general principle is using separate sources, which is a broader and more accurate answer.
B. Connecting to a single PDU, even a redundant one, can still be a single point of failure if the PDU's input power or the unit itself fails.
D. This configuration offers no protection against a power source failure and completely defeats the purpose of having redundant power supplies.

1. Cisco Nexus 9300-EX, 9300-FX/FX2/FX3/FXP, and 9300-GX Platform Hardware Installation Guide. "Power Supply Redundancy" section. It states, "For redundancy, you must connect each power supply to a separate power source."

2. Cisco Nexus 7000 Series Hardware Installation and Reference Guide. Chapter: "Installing and Removing a Power Supply Unit," Section: "Power Supply Redundancy." The guide specifies connecting power supplies to independent AC or DC power sources for N+1 and N+N redundancy.

3. Cisco Nexus 5600 Platform Hardware Installation Guide. Chapter: "Installing the Switch," Section: "Power Supply Requirements." It explicitly states, "For power redundancy, you must connect each power supply to a separate circuit."