Understanding Cisco Catalyst StackPower
Cisco StackPower creates a shared DC power backplane across multiple Catalyst switches, aggregating their individual power supplies into a single, managed power pool.
Instead of treating each switch's power supply unit (PSU) as an isolated island, StackPower allows a switch with high PoE demand—or a failed power supply—to draw dynamic DC power from other members in the power stack.
Core Concepts & Architecture
- Power Pooling: All connected PSUs contribute to a unified power budget for system operations and Power over Ethernet (PoE).
- Topology Limits: Up to 4 switches can be directly cabled together in a ring topology. For larger setups (up to 8 switches), a star topology using a Cisco eXpandable Power System (XPS 2200) is required.
- Data Stack vs. Power Stack: StackWise (data stack) supports up to 8 switches, meaning a full 8-switch StackWise stack is typically divided into two separate 4-switch StackPower rings.
Operating Modes
Both modes can be enforced in Strict (loads are proactively shed if potential budget exceeds capacity) or Non-Strict(over-allocation allowed as long as actual live draw stays under budget).
Key Operational Benefits
- Zero-Footprint Redundancy (1+N): Eliminates the need for external redundant power supplies (RPS) or dual PSUs in every chassis. A 4-switch stack can achieve complete power redundancy using only 5 or 6 PSUs across the entire ring instead of 8.
- Intelligent Load Shedding: If total available power drops below consumption (e.g., an AC breaker trips), the stack intelligently cuts power to low-priority PoE ports or switches first, keeping core infrastructure and critical devices online.
- Pay-as-You-Grow: You can deploy switches with lower-wattage power supplies initially and dynamically add PSUs to any member of the stack as PoE requirements increase.
Supported Platforms
StackPower requires specialized hardware-level power distribution buses. It is supported on Catalyst 3750-X, 3850, 9300, and 9300X fixed campus switches (Note: Catalyst 9300L variants do not support StackPower).
