Cisco Systems WSC2960X48TDL manual Powered-Device Detection and Initial Power Allocation, Class

Page 89

Configuring PoE

Power over Ethernet Ports

Powered-Device Detection and Initial Power Allocation

The switch detects a Cisco pre-standard or an IEEE-compliant powered device when the PoE-capable port is in the no-shutdown state, PoE is enabled (the default), and the connected device is not being powered by an AC adaptor.

After device detection, the switch determines the device power requirements based on its type:

•A Cisco prestandard powered device does not provide its power requirement when the switch detects it, so a switch that does not support PoE+ allocates 15.4 W as the initial allocation for power budgeting; a PoE+ switch allocates 30 W (PoE+).

The initial power allocation is the maximum amount of power that a powered device requires. The switch initially allocates this amount of power when it detects and powers the powered device. As the switch receives CDP messages from the powered device and as the powered device negotiates power levels with the switch through CDP power-negotiation messages, the initial power allocation might be adjusted.

•The switch classifies the detected IEEE device within a power consumption class. Based on the available power in the power budget, the switch determines if a port can be powered. Table 10: IEEE Power Classifications, on page 77 lists these levels.

Table 10: IEEE Power Classifications

 

Class

Maximum Power Level Required from the Switch

0 (class status unknown)

15.4 W

1

4 W

2

7 W

3

15.4 W

4

30 W PoE+ devices only

The switch monitors and tracks requests for power and grants power only when it is available. The switch tracks its power budget (the amount of power available on the switch for PoE). The switch performs power-accounting calculations when a port is granted or denied power to keep the power budget up to date.

After power is applied to the port, the switch uses CDP to determine the CDP-specificpower consumption requirement of the connected Cisco powered devices, which is the amount of power to allocate based on the CDP messages. The switch adjusts the power budget accordingly. This does not apply to third-party PoE devices. The switch processes a request and either grants or denies power. If the request is granted, the switch updates the power budget. If the request is denied, the switch ensures that power to the port is turned off, generates a syslog message, and updates the LEDs. Powered devices can also negotiate with the switch for more power.

With PoE+, powered devices use IEEE 802.3at and LLDP power with media dependent interface (MDI) type, length, and value descriptions (TLVs), Power-via-MDA TLVs, for negotiating power up to 30 W. Cisco pre-standard devices and Cisco IEEE powered devices can use CDP or the IEEE 802.3at power-via-MDI power negotiation mechanism to request power levels up to 30 W.

Catalyst 2960-X Switch Interface and Hardware Component Configuration Guide, Cisco IOS Release 15.0(2)EX

OL-29034-01

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Contents First Published July 10 Americas HeadquartersPage N T E N T S Contents Configuring Auto-MDIX41 Configuring System MTU Configuring EEE Viii Bold font Document ConventionsConvention Description Reader Alert Conventions Vertical barsElement Related Documentation Obtaining Documentation and Submitting a Service RequestXii This chapter contains the following topics Information About Using the Command-Line InterfaceCommand Modes Configure Mode Access Method Prompt Exit Method About This ModeQuit Ctrl-ZCommand or Action Purpose Step Using the Help SystemMode HelpCLI Error Messages Understanding Abbreviated CommandsNo and default Forms of Commands Configuration Logging How to Use the CLI to Configure FeaturesConfiguring the Command History Error Message MeaningCommand or Action Changing the Command History Buffer SizeRecalling Commands Disabling the Command History Feature Enabling and Disabling Editing FeaturesPrivileged Exec mode Terminal no historyEditing Commands through Keystrokes Editing Command Lines That Wrap Access-list Searching and Filtering Output of show and more CommandsShow more command begin include exclude regular-expression Show more command begin include excludeCommand or Action Example OL-29034-01 Information About Configuring Interface Characteristics Finding Feature InformationInterface Types This module contains the following topicsPort-Based VLANs Switch PortsTrunk Ports Switch Virtual InterfacesEtherChannel Port Groups Power over Ethernet PortsUSB Mini-Type B Console Port Using the Switch USB PortsUSB Type a Ports Interface ConnectionsConnecting VLANs with the Switch Interface Configuration ModeFeature Default Ethernet Interface ConfigurationDefault Setting Layer 2 or switching mode switchport command VLANs 1Speed and Duplex Configuration Guidelines Interface Speed and Duplex ModeIeee 802.3x Flow Control Configuring Interfaces Procedure How to Configure Interface CharacteristicsGigabit Ethernet port 1 on switch 1 is selected Either gigabitethernet 1/0/1Adding a Description for an Interface Configure terminalDescription string Show interfaces interface-id descriptionInterface range port-rangemacro Configuring a Range of InterfacesConfigure terminal Enters global configuration mode Define interface-range macroname Configuring and Using Interface Range MacrosVerifies the configuration of the interfaces in the range Interface range macro macroname Configuring Ethernet InterfacesSetting the Interface Speed and Duplex Parameters Nonegotiate Speed 10 100 1000 auto 10Command or Action Purpose Configuring Ieee 802.3x Flow ControlEnter interface configuration mode Configuring SVI Autostate ExcludeEnd Returns to privileged Exec mode Shutting Down and Restarting the Interface Switchport autostate excludeAn SVI line state up or down Interface vlan vlan-id gigabitethernet interface-idThis configuration applies to all switches in a stack Configuring the Console Media TypeConfigure terminal Line console Media-type rj45 End Shutdown Shuts down an interfaceConfigure terminal Enters the global configuration mode Configuring the USB Inactivity TimeoutCommand Purpose Monitoring Interface CharacteristicsShow interfaces interface-id status err-disabled Show interfaces interface-id switchportClearing and Resetting Interfaces and Counters Identifying Interfaces on a Stack-Capable Switch Examples Configuration Examples for Interface CharacteristicsConfiguring a Range of Interfaces Examples Adding a Description to an Interface ExampleConfiguring the Console Media Type Example Configuring and Using Interface Range Macros ExamplesSetting Interface Speed and Duplex Mode Example To disable the configuration, use these commands Configuring the USB Inactivity Timeout ExampleStandards and RFCs Standard/RFC NoneRelease Modification Cisco IOS Release 15.02EX This feature was introducedTechnical Assistance Description Link OL-29034-01 This module contains the following sections Prerequisites for Auto-MDIXRestrictions for Auto-MDIX How to Configure Auto-MDIX Information about Configuring Auto-MDIXConfiguring Auto-MDIX on an Interface Auto-MDIX on an InterfaceMonitoring Auto-MDIX This example shows how to enable auto-MDIX on a port Example for Configuring Auto-MDIXInformation about the Ethernet Management Port Prerequisites for Ethernet Management PortsSupported Features on the Ethernet Management Port Ethernet Management Port Direct Connection to a SwitchDisabling and Enabling the Ethernet Management Port How to Configure the Ethernet Management PortWhat to Do Next Additional ReferencesRelated Topic Bootloader commandsMIBs Document TitleOL-29034-01 Configuring LLDP, LLDP-MED, and Wired Location Service Lldp and Cisco Medianet Lldp and Cisco Switch StacksLldp Supported TLVs LLDP-MED Supported TLVs Wired Location Service Configuration Guidelines Default Lldp ConfigurationLldp run Enables Lldp globally on the switch Configure terminal Lldp runLLDP, and enter interface configuration mode Enabling LldpLldp transmit Enables the interface to send Lldp packets Configuring Lldp CharacteristicsLldp receive Enables the interface to receive Lldp packets Show lldp Verifies the configurationSwitchconfig# lldp holdtime Command or Action Purpose Step Configuring LLDP-MED TLVsLldp med-tlv-select Specifies the TLV to enable Lldp med-tlv-select End Copy running-config startup-configConfiguration mode. The range is 1 to Configuring Network-Policy TLVDscp dvalue none untagged Voice voice-signalingvlan vlan-idcosShow network-policy profile Verifies the configuration Configuring Location TLV and Wired Location ServiceWay Use one of the followingInformation, and enter interface configuration mode Exit Returns to global configuration modeUse one of the following Verifies the configuration Enters location information for an interfaceCommand or Action Purpose Example Enabling Wired Location Service on the SwitchNmsp notification interval attachment location Configuring Network-Policy TLV ExamplesNmsp enable Enables the Nmsp features on the switch Command Description Civic location OL-29034-01 System MTU Guidelines Information about the MTUConfiguring the System MTU How to Configure MTU SizesReload Reloads the operating system Configuration Examples for System MTUShow system mtu Verifies your settings Additional References for System MTU Restrictions for PoE Configuring PoESupported Protocols and Standards Power over Ethernet PortsInformation about PoE Class Powered-Device Detection and Initial Power AllocationPower Management Modes Power Monitoring and Power Policing Maximum Power Allocation Cutoff Power on a PoE Port Configuring a Power Management Mode on a PoE Port How to Configure PoENever static max max-wattage Budgeting Power for Devices Connected to a PoE PortShow power inline No cdp run Optional Disables CDP Budgeting Power to All PoE portsConfigure terminal No cdp run Budgeting Power to a Specific PoE PortPower inline consumption wattage Configuring Power PolicingSpecifies the physical port to be configured, and enter Show power inline police Show errdisable recovery Power inline police actionlog errdisable ExitConfiguration mode Power inline police actionlog errdisableDown the port and puts the port in the error-disabled state Power inline police action log-Generates a syslog messageWhile still providing power to the port Budgeting Power Example Monitoring Power StatusConfiguration Examples for Configuring PoE EEE Overview Information About EEEDefault EEE Configuration How to Configure EEEEEE is disabled by default Restrictions for EEEPower efficient-ethernet auto Specifies the interface to be configured, and enterCommand Monitoring EEEThis example shows how to disable EEE for an interface Configuration Examples for Configuring EEEThis example shows how to enable EEE for an interface Feature History and Information for Configuring EEE OL-29034-01 D E PoE
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