Cisco IE 4000, Software Configuration Manual

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21
Configuring Interfaces
Understanding Interface Types
ports into one logical access port, group multiple tunnel ports into one logical tunnel port, or group multiple routed ports
into one logical routed port. Most protocols operate over either single ports or aggregated switch ports and do not
recognize the physical ports within the port group. Exceptions are the Cisco Discovery Protocol (CDP), Link Aggregation
Control Protocol (LACP), and the Port Aggregation Protocol (PAgP), which operate only on physical NNI or ENI ports.
When you configure an EtherChannel, you create a port-channel logical interface and assign an interface to the
EtherChannel. For Layer 3 interfaces, you manually create the logical interface by using the
interface port-channel
global configuration command. Then you manually assign an interface to the EtherChannel by using the channel-group
interface configuration command. For Layer 2 interfaces, use the channel-group interface configuration command to
dynamically create the port-channel logical interface. This command binds the physical and logical ports together. For
more information, see
Configuring EtherChannels, page 1027
Power over Ethernet Ports
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)

802.3af/802.3at-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.
After the switch detects a powered device, it determines the device power requirements and then grants or denies power
to the device. The switch can also sense the real-time power consumption of the device by monitoring and policing the
power usage.
This section has this PoE information:

Supported Protocols and Standards, page 21

Powered-Device Detection and Initial Power Allocation, page 22

Power Management Modes, page 22
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.
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/802.3at—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.