Poe Configuration Considerations - Cisco Small Business 200 Series Administration Manual

Port Management: PoE
PoE on the Device
Power over Ethernet can be used in any enterprise network that deploys relatively low-powered devices
connected to the Ethernet LAN, such as:
• IP phones
• Wireless access points
• IP gateways
• Audio and video remote monitoring devices
PoE Operation
PoE implements in the following stages:
• Detection—Sends special pulses on the copper cable. When a PoE device is located at the other
end, that device responds to these pulses.
• Classification—Negotiation between the Power Sourcing Equipment (PSE) and the Powered Device
(PD) commences after the Detection stage. During negotiation, the PD specifies its class that is the
amount of maximum power that the PD consumes.
• Power Consumption—After the classification stage completes, the PSE provides power to the PD. If
the PD supports PoE, but without classification, it is assumed to be class 0 (the maximum). If a PD
tries to consume more power than permitted by the standard, the PSE stops supplying power to the
port.
PoE supports two modes:
• Port Limit—The maximum power the device agrees to supply is limited to the value the system
administrator configures, regardless of the Classification result.
• Class Power Limit—The maximum power the device agrees to supply is determined by the results
of the Classification stage. This means that it is set as per the Client's request.

PoE Configuration Considerations

There are two factors to consider in the PoE feature:
• The amount of power that the PSE can supply
• The amount of power that the PD is actually attempting to consume
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