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Software Configuration Guide—Release 12.2(25)SG
OL-7659-03
Chapter7 Environmental Moni toring and Power Management
Power Management
If you attempt to insert additional modules into your switch and exceed the power supply, the switch
immediately places the newly inserted module into reset mode, and th e switch displays these error
messages:
Module has been inserted
Insufficient power supplies operating.
Additionally, if you power down a functioning switch and insert an additional module or change the
module configuration so that the power requirements exceed the available power, one or more
modules enter reset mode when you power on the switch again.
•The power requirements for the PoE exceed the PoE provided by the power supplies.
If you have too many IP phones drawing power from the system, power to IP phones is cut, and some
phones may be powered down to reduce the power requirements to match the power supplie s.
In the first scenario (power requirements exceed the power supplied), the system attempts to resolve this
power usage limitation by evaluating the type and number of modules installed. During the evaluation
cycle, beginning from the bottom of the chassis, the system puts the modules that it is un able to support
(for lack of power) into reset mode. The supervisor engine and modules for which there is adequate
power always remain enabled, with no disruption of network connectivity. Modules placed in reset mode
still consume some power and can be removed from the chassis to further reduce power requirem ents. If
you configure the chassis correctly, the system will not enter the evaluation cycle.
A module in reset mode continues to draw power as long as it is installed in the chassis; you can use the
show power module command to determine how much power is required to bring the module online.
To compute the power requirements for your system and verify that your system has enough power, add
the power consumed by the supervisor engine module(s), the fan box(es) , and the installed modules
(including PoE). For PoE, total the requirements for all the phones. See the “Powering Down a Module”
section on page 7-19 for more information on th e power consumption for the various components of your
switch.
The 802.3af-compliant PoE modules can consume up to 20 W of PoE to power FPGAs and other
hardware components on the module. Be sure to add at least 20 W to your PoE requirements for each
802.3af-compliant PoE module to ensure that the system has adequate power for the PDs connected to
the switch.
On the WS-X4148-RJ45V PoE module, PoE consumption cannot be me asured. Therefore, for all PoE
calculations, the PoE consumption on this module is pre sumed to be equal to its administrative PoE.
You can use the show module command to verify which modules are active and which, if any, have been
placed in reset.
The following example shows the show module command output for a system with inadequate power
for all installed modules. The system does not have enough power for Module 5; the “Status” displays
it as “PwrDeny.”
If the PoE that is consumed by the module is more than 50 W above the PoE you allocated using the
power inline consumption default command, the “Status” displays as “PwrOver.” If the PoE consumed
by the module is more than 50 W above the PoE module limit, the “Status” displays as “PwrFault.”
Switch# show module
Mod Ports Card Type Model Serial No.
----+-----+--------------------------------------+-----------------+-----------
1 2 1000BaseX (GBIC) Supervisor(active) WS-X4014 JAB054109GH
2 6 1000BaseX (GBIC) WS-X4306 00000110
3 18 1000BaseX (GBIC) WS-X4418 JAB025104WK
5 0 Not enough power for module WS-X4148-FX-MT 00000000000
6 48 10/100BaseTX (RJ45) WS-X4148 JAB023402RP