Cisco WS-SUP32-GE-3B Software Configuration Guide - Page 206

Understanding Cisco IP Phone Support Chapter 14 Configuring Cisco IP Phone Support With an inline power card installed, a switching module can automatically detect and provision a powered device that adheres to a PoE implementation supported by the card. The switching module can supply power to devices supporting other PoE implementations only through manual configuration. Only one device can be powered per port, and the device must be connected directly to the switch port. For example, if a second IP phone is daisy-chained off a phone that is connected to the switch port, the second phone cannot be powered by the switch. Note For information about switching modules that support inline power, refer to the Release Notes for Cisco IOS Release 12.2ZY on the Supervisor Engine 32 PISA publication at this URL: http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2ZY/release/notes/ol_13011.html Inline Power Management Each inline-powered device, such as an IP phone or a wireless access point, requires power to be allocated from the chassis power budget. Because each powered device can have unique power requirements, more devices can be supported if the system's power management software can intelligently allocate the necessary power on a per-port basis. With Release 12.2ZYA and later releases, you can configure the switching module to allocate and apply inline power to individual ports in these situations: • When an attached inline-powered device is discovered, at a power level based on information sensed from the device or at a default or specified maximum power level (auto mode) • At a fixed default or specified level, whether or not an inline-powered device is present on the port (static mode) The Cisco prestandard PoE implementation defines a method to sense an attached inline-powered device and to apply an initial power level. After activation, a Cisco prestandard device that supports CDP can negotiate a lower or higher power allocation using CDP messaging. The IEEE 802.3af PoE standard defines a method to sense an attached device and to immediately classify the device's power requirement into three power ranges: • Class 1: Up to 4 W per port • Class 2: Up to 7 W per port • Class 3: Up to 15.4 W per port The IEEE standard contains no provision for subsequent readjustment of a device's power allocation. Cisco inline-powered devices that support IEEE 802.3af and CDP can use CDP to override the IEEE 802.3af power classification. A switching module whose inline power card supports both PoE implementations will attempt both detection methods in parallel. If the attached device responds to both detection methods, the module will consider the device to be an IEEE 802.3af device. Caution When an IP phone cable is plugged into a port and the power is turned on, the supervisor engine has a 4-second timeout waiting for the link to go up on the line. During those 4 seconds, if the IP phone cable is unplugged and a network device is plugged in, the network device could be damaged. We recommend that you wait at least 10 seconds between unplugging a network device and plugging in another network device. 14-4 Catalyst Supervisor Engine 32 PISA Cisco IOS Software Configuration Guide, Release 12.2ZY OL-11439-03