CHAPT ER
9-1
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
9
Configuring Catalyst 3750-X StackPower
The Catalyst 3750-X and 3560-X switches have two power supplies per system, allowing the power load
to be split between them. This accommodates the increased maximum power of 30 watts per port
provided to a powered device to meet the PoE+ standard (802.3at). With PoE+, a 48-port system would
need 1440 Watts to provide 30 Watts per powered device for the PoE ports. Systems with fewer powered
devices might require only one power supply. In this case, the additional power supply can provide
one-to-one redundancy for the active supply.
In addition, the Catalyst 3750-X stackable switch supports StackPower, which allows the power supplies
to share the load across multiple systems in a stack. By connecting the switches with power stack cables,
you can manage the power supplies of up to four stack members as a one large power supply that
provides power to all switches and to the powered devices connected to switch ports. Since power
supplies are most effective when running at 30 to 90% of their maximum load, taking some of the power
supplies offline provides maximum power efficiency. Switches in a power stack must be members of the
same switch (data) stack.
A power stack cannot contain more than four switches. If you merge two stacks, the total number of
switches cannot exceed four.
Note StackPower is not supported in switches running the LAN base feature set.
See the hardware installation guide for information on designing and connecting the power stack. For
more information about PoE ports, see the “Power over Ethernet Ports” section on page 13-7 in the
chapter on Configuring Interfaces. For more information about the commands in this chapter, see the
command reference for this release.
This chapter includes these sections:
Understanding StackPower, page 9-1
Configuring Stack Power, page 9-6

Understanding StackPower

Some reasons for connecting individual switches in a power stack are:
In case of power supply failure, if there is enough spare power budget in the rest of the power stack,
switches can continue to function.
You can replace a defective power supply without having to shut down all powered devices in the
systems.