2-8
Catalyst 3850 Switch Hardware Installation Guide
OL-26779-02
Chapter 2 Switch Installation
Planning a StackPower Stack
• If some switches in the stack are completely separated from the stack, a stack split can take occur.
• A stack split can occur on a full ring stack if:
–
More than one running switch is removed without powering down.
–
More than one stack cable is removed without powering down.
• A stack split can occur in a partial ring stack if:
–
A switch is removed without powering down.
–
A stack cable is removed without powering down.
• In a split stack, depending on where the active and standby switches are located, either two stacks
might be formed (with the standby taking over as the new active switch in the newly formed stack)
or all the members in the newly formed stack might reload.
Note These results depend on how the switches are connected. You can remove two or more switches
from the stack without splitting the stack.
For conditions that can cause a stack reelection or to manually elect the active switch, see the stacking
software configuration guide on Cisco.com at this URL:
http://www.cisco.com/go/cat3850_docs
Planning a StackPower Stack
Catalyst 3850 switches can share power by using the StackPower feature.
• StackPower Stacking Guidelines, page 2-8
• StackPower Cabling Configurations, page 2-9
StackPower Stacking Guidelines
You can configure a StackPower stack for either power sharing or redundancy. In power-sharing mode,
the power of all the power supplies in the stack is aggregated and distributed among the stack members.
In redundant mode, when the total power budget of the stack is calculated, the wattage of the largest
power supply is not included. That power is held in reserve and used to maintain power to switches and
attached devices when one power supply fails. Following the failure of a power supply, the StackPower
mode becomes power sharing.
Note Power-sharing mode is the recommended configuration for Catalyst 3850 switches.
For general concepts and management procedures for switch power stacks, see the software stacking
configuration guide on Cisco.com.
Before connecting the switches in a power stack, keep in mind these guidelines:
