CHAPTER
1-1
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-25303-03
1
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 Cisco 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.
The Cisco eXpandable Power System (XPS) 2200 is a standalone power system that you can connect to
Catalyst 3560-X and Catalyst 3750-X switches that are running Cisco IOS Release 12.2(55)SE1 and
later. The XPS 2200 can provide backup power to connected devices that experience a power supply
failure or, in a Catalyst 3750-X power stack, it can supply additional power to the power stack budget.
For more information about the XPS 2000, see the configuration notes on Cisco.com:
http://www.cisco.com/en/US/docs/switches/power_supplies/xps2200/software/configuration/note/ol24
241.html
The XPS 2200 power ports and internal power supplies can operate in redundant power supply (RPS)
mode or stack power (SP) mode. Stack-power mode is used only on Catalyst 3750-X switches in a power
stack. With no XPS, a power stack operates in ring topology with a maximum of four switches in the
stack. If you merge two stacks, the total number of switches cannot exceed four. When an XPS is in the
power stack, you can connect up to nine switches in the stack plus the XPS, providing power budgets to
power stack members similar to stack-power ring topology operation.
All Catalyst 3750-X switches connected to an XPS on SP ports are part of the same power stack, and all
power from the XPS and the switches is shared across all switches in the stack. Power sharing is the
default mode, but the XPS supports the same stack power modes that are supported in a ring topology
(strict and nonstrict power-sharing or redundant modes).
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 1-7 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 Cisco StackPower, page 1-2
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