11-7
Catalyst 3560 Switch Software Configuration Guide
OL-8553-06
Chapter 11 Configuring Interface Characteristics
Understanding Interface Types
Power over Ethernet Ports
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:
• Supported Protocols and Standards, page 11-7
• Powered-Device Detection and Initial Power Allocation, page 11-7
• Power Management Modes, page 11-8

Supported Protocols and Standards

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.

Powered-Device Detection and Initial Power Allocation

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.