15-5
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Chapter 15 Configuring Power over Ethernet
Configuring Power Consumption for Powered Devices on an Interface
Configuring Power Consumption for Powered Devices on an
Interface
By default, when the switch detects a powered device on an interface, it assumes the powered device
consumes the maximum the port can provide (7 W on a legacy PoE module and 15.4W on the IEEE PoE
modules introduced in Cisco IOS Release 12.2(18)EW). When the switch receives a CDP packet from
the powered device, the wattage automatically adjusts downward to the specific amount required by that
device. Normally, this automatic adjustment works well, and no further configuration is required or
recommended. However, you can specify the powered device's consumption for a particular interface to
provide extra functionality from your switch. This behavior is useful when CDP is disabled or not
available.
Note When manually configuring the consumption for powered devices, you need to account for the power
loss over the cable between the switch and the powered device.
Note The inline power consumption command overrides the power allocated to the port through IEEE/Cisco
phone discovery and CDP/LLDP power negotiation. To guarantee safe operation of the system, ensure
that the value configured here is no less than the actual power requirement of the attached device. If the
power drawn by the inline powered devices exceeds the capability of the power supply, it could trip the
power supply.
To change the power consumption of a single powered device, perform this task:
This example shows how to set the PoE consumption to 5000 milliwatts for interface gi 7/1 regardless
what is mandated by the 802.3af class of the discovered device, or by any CDP packet received from the
powered device. This example also verifies the PoE consumption on interface gi 7/1.
The following output displays the initial power consumption of the interface:
Switch# show power inline gi 7/1
Available:627(w) Used:267(w) Remaining:360(w)
Interface Admin Oper Power(Watts) Device Class
From PS To Device
--------- ------ ---------- ---------- ---------- ------------------- -----
Gi7/1 auto on 7.9 7.0 IP Phone 7941 3
Command Purpose
Step 1
Switch(config)# interface {fastethernet |
gigabitethernet} slot/port
Selects the interface to configure.
Step 2
Switch(config-if)# [no] power inline
consumption milli-watts
Sets the PoE consumption (in milliwatts) of the powered
device connected to a specific interface. The power
consumption can range from 4000 to 15,400.
To reenable the automatic adjustment of consumption, either
use the no keyword or specify 15,400 milliwatts.
Step 3
Switch(config-if)# end
Exits configuration mode.
Step 4
Switch# show power inline consumption
{fastethernet | gigabitethernet} slot/port
Displays the PoE consumption for the interface.
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