Cisco WS-C2980G-A Software Guide - Page 432
Inline Power Management Modes, Power Requirements
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Understanding How Inline Power Works Chapter 28 Power Management Inline Power Management Modes Each port is configured through the CLI, SNMP, or a configuration file in one of the following modes (configured through the set port inlinepower CLI command): • Auto-The supervisor engine directs the switching module to power up the port only if the switching module discovers that the phone and the switch have enough power. You can specify the maximum wattage that is allowed on the port. If you do not specify a wattage, then the switch delivers no more than the hardware-supported maximum value. • Static-The supervisor engine directs the switching module to power up the port to the wattage you specify only if the switching module discovers the phone. You can specify the maximum wattage that is allowed on the port. If you do not specify a wattage, then the switch allows the hardware-supported maximum value. The maximum wattage, whether determined by the switch or specified by you, is preallocated to the port. If the switch does not have enough power for the allocation, the command will fail. • Off-The supervisor engine does not direct the switching module to power up the port even if an unpowered phone is connected. Each port has a status that is defined as one of the following: • on-Power is supplied by the port. • off-The power is not supplied by the port. • Power-deny-The supervisor engine does not have enough power to allocate to the port, or the power that is configured for the port is less than the power that is required by the port. The power is not being supplied by the port. • err-disable-The port cannot provide power to the connected device that is configured in Static mode. • faulty-The port failed diagnostic tests. Power Requirements Each powered device has different power requirements. Table 28-4 lists the power requirements for the different classes of IP phones and several other powered devices. The supervisor engine initially calculates the power allocation for each port based on the per-port configuration and default power allocation. If the correct amount of power is determined from the CDP messaging with the Cisco-powered device, the supervisor engine reduces or increases the allocated power for any ports that are set to Auto mode. Allocated power is not adjusted for ports that are set to Static mode. For example, the default allocated power is 7 W for a Cisco IP Phone requiring 6.3 W. The supervisor engine allocates 7 W for the Cisco IP Phone and powers it up. After the Cisco IP Phone is operational, it sends a CDP message with the actual power requirement to the supervisor engine. The supervisor engine then decreases the allocated power to the required amount if the port is set to Auto mode. 28-12 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 78-15486-01