Cisco Systems 3560 Manual De Usuario

Catalyst 3560 PoE-capable switch ports automatically supply power to these connected devices (if the 
switch senses that there is no power on the circuit):

Cisco pre-standard powered devices (such as Cisco IP Phones and Cisco Aironet access points)

IEEE 802.3af-compliant powered devices 

A powered device can receive redundant power when it is connected only to a PoE switch port and to an 
AC power source.

This section has this PoE information:

The switch uses these protocols and standards to support PoE:

CDP with power consumption—The powered device notifies the switch of the amount of power it 
is consuming. The switch does not reply to the power-consumption messages. The switch can only 
supply power to or remove power from the PoE port.

Cisco intelligent power management—The powered device and the switch negotiate through 
power-negotiation CDP messages for an agreed power-consumption level. The negotiation allows a 
high-power Cisco powered device, which consumes more than 7 W, to operate at its highest power 
mode. The powered device first boots up in low-power mode, consumes less than 7 W, and 
negotiates to obtain enough power to operate in high-power mode. The device changes to 
high-power mode only when it receives confirmation from the switch.

High-power devices can operate in low-power mode on switches that do not support 
power-negotiation CDP. 

Before Cisco IOS Release 12.2(25)SE, Catalyst 3560 PoE-capable switches (without intelligent 
power management support) caused high-power powered devices that supported intelligent power 
management to operate in low-power mode. Devices in low-power mode are not fully functional.

Cisco intelligent power management is backward-compatible with CDP with power consumption; 
the switch responds according to the CDP message that it receives. CDP is not supported on 
third-party powered devices; therefore, the switch uses the IEEE classification to determine the 
power usage of the device.

IEEE 802.3af—The major features of this standard are powered-device discovery, power 
administration, disconnect detection, and optional powered-device power classification. For more 
information, see the standard.

The switch detects a Cisco pre-standard or an IEEE-compliant powered device when the PoE-capable 
port is in the no-shutdown state, PoE is enabled (the default), and the connected device is not being 
powered by an AC adaptor.