Cisco Catalyst 3850 - StackPower.

Just wanted to make a note about Catalyst 3850 and StackPower feature.

Cisco Catalyst 3850 Series Switches:

StackPower allows customers to simply add one extra power supply in any switch of the stack and either provide power redundancy for any of the stack members or simply add more power to the shared pool. StackPower eliminates the need for an external redundant power system or installation of dual power supplies in all the stack members. StackPower is available in LAN Base license level (or higher). For LAN Base, cables need to be purchased separately.

Switch#show license right-to-use usage
 Slot#  License Name     Type     usage-duration(y:m:d)  In-Use  EULA
 1      ipservices     permanent    0 :0 :0                no    no
 1      ipservices     evaluation   0 :0 :0                no    no
 1      ipbase         permanent    0 :0 :0                no    no
 1      ipbase         evaluation   0 :0 :0                no    no
 1      lanbase        permanent    0 :6 :21               yes   yes
 1      apcount        evaluation   0 :0 :0                no    no
 1      apcount        base         0 :0 :0                no    no
 1      apcount        adder        0 :0 :0                no    no


Cisco Catalyst 3850 Series Switches > Q&A:

• Q. Do I need to populate all of the power supply slots in my switch?
• A. No. The Cisco Catalyst 3850 switches provide two slots for the use of redundant power supplies, but only one supply is needed to run a single switch unless full PoE+ is deployed on a 48-port switch. In that case, the power requirement is about 1700W, which is more than the 1100W provided by the largest available power supply. If the switch is deployed within a Cisco StackPower stack, a second power supply might not be needed if the stack has extra power to meet the requirements of this switch, though the power supply slot must be covered to maintain proper airflow.

• Q. Can you give priority to an important switch in the stack?
• A. The Cisco StackPower solution assigns a default priority to the switches in a stack as well as to the ports (high or low) of every switch. The administrator has the ability to change and program these priorities with “power-priority switch <1-27>” and “power-priority low | high <1-27>” configuration commands.

All you need is just enough cables: CAB-SPWR-30CM (37-1122-01) - $15 each on Ebay.

Example for a stack of two switches

Real example for a stack of two switches (WS-C3850-48T, without PoE) with only one power supply installed in each device (PWR-C1-350WAC entry level ones, by default). To get a power redundancy you can order two power supplies OR only one cable CAB-SPWR-30CM, connect it as you want, I did the following - port1 to port1. Technically, it will work without any further configuration. If you connect a power supply of any of the nodes, two switches will be powered, it means to get two switches powered, you need to connect anyone of the nodes. If you want you can add the following configuration:

stack-power stack StackPower
 mode power-shared

stack-power switch 1
 stack StackPower
 power-priority switch 1

stack-power switch 2
 stack StackPower
 power-priority switch 2

Here you can find a video from Cisco regarding StackPower in action - Cisco Catalyst 3750-X StackPower.

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