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Software Configuration Guide—Release IOS XE 3.3.0SG and IOS 15.1(1)SG
OL-25340-01
Chapter 12 Environmental Monitoring and Power Management
Power Management
• Combined mode—Combined mode uses the power from all installed power supplies to support the
switch configuration power requirements. However, combined mode has no power redundancy. If a
power supply fails, one or more modules might shut down.
Note On the Catalyst 4510R switch, the 1000 W AC power supply is not enough to support redundant
mode for all possible configurations. It is able to support redundant mode for limited
configurations that require less than 1050 W.
Note The 1400 W DC power supply supports combined mode for data power. It does not support
combined mode for PoE power.
Selecting a Power Management Mode
By default, a switch is set to redundant mode. In the show power command, if the
power supplies needed by system is 1, the switch is in redundant mode; if the
power supplies needed by system is 2, the switch is in combined mode.
Your switch hardware configuration dictates which power supply or supplies you should use. For
example, if your switch configuration requires more power than a single power supply provides, use the
combined mode. In combined mode, however, the switch has no power redundancy. Consider the
following possibilities:
• The supervisor engine consumes 110 W, the fan boxes for the Catalyst 4503 switch consume 30 W
each, the fan boxes for the Catalyst 4506 and Catalyst 4507 switches consume 50 W each, the
backplane for the Catalyst 4503 and Catalyst 4506 switches consumes 10 W, and the backplane for
the Catalyst 4507 switch consumes 40 W.
• 1000 W can support a fully loaded Catalyst 4503 switch with no powered device support.
• 1300 W can support a fully loaded Catalyst 4503 switch with Cisco powered devices.
• Each PoE port on a WS-X4148-RJ45V module requires 6.3 W. Five fully loaded WS-X4148-RJ45V
modules in a switch comprise 240 ports. This configuration requires 1512 W of PoE, plus 300 W for
the modules.
Power Management Limitations in Catalyst 4500 Series Switches
Limitation 1
It is possible to configure a switch that requires more power than the power supplies provide. The two
ways you could configure a switch to exceed the power capabilities are as follows:
• The power requirements for the installed modules exceed the power provided by the power supplies.
If you insert a single power supply and then set the switch to combined mode, the switch displays
this error message:
Insufficient power supplies present for specified configuration.
This error message also displays in the output for the show power command. This error message
displays because, by definition, combined mode requires that two working power supplies be
installed in your switch.
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