Cisco SR224T Administration Guide - Page 149

Managing Power-over-Ethernet Devices PoE on the Switch 11 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, which 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 switch agrees to supply is limited to the value the system administrator configures, regardless of the Classification result. • Class Power Limit-The maximum power the switch 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 Cisco Small Business 200 Series Smart Switch Administration Guide 150