Cisco 4500M

7-11
Software Configuration Guide—Release 12.2(25)EW
OL-6696-01
Chapter 7 Environmental Monitoring and Power Management
Power Management
• The software automatically adjusts between system power (for modules, backplane, and fans) and
PoE. Although PoE is 96 percent efficient, system power has only 75 percent efficiency. For
example, each 120 W of system power requires 160 W from the DC input. This requirement is
reflected in the “Power Used” column of the output for the show power available command.
• The 1400 W DC power supply does not support combined mode. If you set the power budget to 2
(combined mode), the switch allows you to configure combined modes but disregards the setting and
remains in redundant mode.
• The 1400 W DC power supply has a separate power on or off switch for PoE. The power supply fan
status and main power supply status are tied together. If either of them fails, both the power supply
and its fan report as bad/off. You should verify that the main power is on before turning on the power
for the inline switch. In addition, you should verify that the power for the inline switch is off before
turning off the main power.
Configuring the DC Input for a Power Supply
To configure the DC input power for the 1400 W DC power supply or a power shelf, perform this task:
The same configuration is applied to both power slots. For example, if you set the dc power input to
1000 W, the switch expects 1000 W as the external DC source for both slot 1and slot 2 (if present)
respectively.
The following example shows how to set the external DC power source to 1000 W:
Switch# configure terminal
Switch (config)# power dc input 1000
Switch (config)# end
Switch#
If you use the 1400 W DC SP power supply in combined mode, the inputs do not have to match.
Special Considerations for the 1400 W DC SP Triple Input Power Supply
Unlike the 1400 W DC power supply, the 1400 W DC SP power supply has sub-modules (multiple
inputs) that can be powered on or off. With Release 12.2(25)EW, the output of the show power command
is modified to display the status of these sub-modules:
Switch# show power
Power Fan Inline
Supply Model No Type Status Sensor Status
------ ---------------- --------- ----------- ------- -------
PS1 PWR-C45-1400DC DCSP1400W good good n.a.
PS1-1 12.5A good
PS1-2 15.0A bad
PS1-3 15.0A off
PS2 none -- -- -- --
Command Purpose
Step 1
Switch# configure terminal
Enters configuration mode
Step 2
Switch(config)# power dc input watts
Sets the capacity of the DC input source.
Step 3
Switch(config)# end
Exits configuration mode.