Catalyst 4500 Series Switch Software Configuration Guide, Release IOS XE 3.3(0)XO

Configuring Power over Ethernet

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Note Before reading this chapter, read the “Preparing for Installation” section of the
Catalyst 4500 Series Installation Guide. You must ensure that your installation site has enough power and cooling to accommodate the additional electrical load and heat introduced by PoE.

This chapter describes how to configure Power over Ethernet (PoE) on the Catalyst 4500 series switch.

This chapter contains the following sections:

• About Power over Ethernet
• Power Management Modes
• Configuring Power Consumption for Powered Devices on an Interface
• Displaying the Operational Status for an Interface
• Displaying all PoE Detection and Removal Events
• Displaying the PoE Consumed by a Module
• PoE Policing and Monitoring
• Enhanced Power PoE Support on the E-Series Chassis

Note For complete syntax and usage information for the switch commands used in this chapter, first look at the Cisco Catalyst 4500 Series Switch Command Reference and related publications at this location:

http://www.cisco.com/en/US/products//hw/switches/ps4324/index.html

If the command is not found in the Catalyst 4500 Series Switch Command Reference, it will be found in the larger Cisco IOS library. Refer to the Cisco IOS Command Reference and related publications at this location:

http://www.cisco.com/en/US/products/ps6350/index.html

About Power over Ethernet

The Catalyst 4500 series switch provides Power over Ethernet (PoE) support for both Cisco Prestandard PoE and the IEEE 802.3af standard (ratified in 2003). PoE is supported by all Catalyst 4500 series chassis and requires a PoE module and power supply. The amount of PoE power available depends on the PoE capabilities of individual power supplies. Support for PoE enables the system to power inline devices, such as IP phones, IP video phones, and wireless access points over standard copper cabling (Category 5, 5e, or 6 cabling).

In addition, with PoE, you do not need to provide wall power for each PoE enabled device. This eliminates the cost for additional electrical cabling that is otherwise necessary for connected devices. Moreover, PoE enables you to isolate critical devices on a single power system, enabling the entire system to be supported by UPS backup.

You typically deploy a Catalyst 4500 series switch in one of two deployment scenarios. The first scenario is data-only, which requires power to operate the switch and the associated modules. The second scenario supports data and PoE (also termed “inline power”) for deployments where the attached device derives power from the Ethernet port.

Catalyst 4500 series switches can sense if a powered device is connected to a PoE module. They can supply PoE to the powered device if there is no power on the circuit. (If there is power on the circuit, the switch does not supply it.) The powered device can also be connected to an AC power source and supply its own power to the voice circuit.

Note You should select the amount of PoE desired using the Cisco Power Calculator:

http://tools.cisco.com/cpc/

Power Management Modes

If your switch has a module capable of providing PoE to end stations, you can set each interface on the module to automatically detect and apply PoE if the end station requires power.

The Catalyst 4500 series switch has three PoE modes:

• auto—PoE interface. The supervisor engine directs the switching module to power up the interface only if the switching module discovers the phone and the switch has enough power. You can specify the maximum wattage that is allowed on the interface. If you do not specify a wattage, then the switch delivers no more than the hardware-supported maximum value. This mode has no effect if the interface is not capable of providing PoE.
• static —High priority PoE interface. The supervisor engine preallocates power to the interface, even when nothing is connected, guaranteeing that power exists for the interface. You can specify the maximum wattage that is allowed on the interface. If you do not specify a wattage, then the switch preallocates the hardware-supported maximum value. If the switch does not have enough power for the allocation, the command fails. The supervisor engine directs the switching module to power up the interface only if the switching module discovers the powered device.
• never —Data interface only The supervisor engine never powers up the interface, even if an unpowered phone is connected. This mode is only needed when you want to make sure power is never applied to a PoE-capable interface.

The switch can measure the actual PoE consumption for an 802.3af-compliant PoE module, and displays this in the show power module command.

PoE consumption cannot be measured on the WS-X4148-RJ45V PoE module. For all PoE calculations, the PoE consumption on this module is presumed to be equal to its administrative PoE.

For more information, see the “Displaying the PoE Consumed by a Module” section.

For most users, the default configuration of “auto” works well, providing plug-and-play capability. No further configuration is required. However, to make an interface higher priority or data only, or to specify a maximum wattage, perform this task:

Note If you set a non-PoE-capable interface to automatically detect and apply power, an error message indicates that the configuration is not valid.

The following example shows how to set the Fast Ethernet interface 4/1 to automatically detect PoE and send power through that interface, and to verify the PoE configuration:

The following example shows how to configure an interface so that it never supplies power through the interface:

Configuring Power Consumption for Powered Devices on an Interface

By default, when the switch detects a powered device on an interface, it assumes the powered device consumes the maximum the port can provide When the switch receives a CDP packet from the powered device, the wattage automatically adjusts downward to the specific amount required by that device. Normally, this automatic adjustment works well, and no further configuration is required or recommended. However, you can specify the powered device's consumption for a particular interface to provide extra functionality from your switch. This behavior is useful when CDP is disabled or not available.

Note When manually configuring the consumption for powered devices, you need to account for the power loss over the cable between the switch and the powered device.

Note The inline power consumption command overrides the power allocated to the port through IEEE/Cisco phone discovery and CDP/LLDP power negotiation. To guarantee safe operation of the system, ensure that the value configured here is no less than the actual power requirement of the attached device. If the power drawn by the inline powered devices exceeds the capability of the power supply, it could trip the power supply.

To change the power consumption of a single powered device, perform this task:

This example shows how to set the PoE consumption to 5000 milliwatts for interface gi 7/1 regardless what is mandated by the 802.3af class of the discovered device, or by any CDP packet received from the powered device. This example also verifies the PoE consumption on interface gi 7/1.

The following output displays the initial power consumption of the interface:

The following output displays the power consumption after entering the power inline consumption command on the interface:

Displaying the Operational Status for an Interface

Each interface has an operational status which reflects the PoE status for an interface. The operational status for an interface is defined as one of the following:

• on—Power is supplied by the port.
• off—Power is not supplied by the port. If a powered device is connected to an interface with external power, the switch does not recognize the powered device. The “Device” column in the show power inline command displays as n/a.
• 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 required by the port; power is not being supplied by the port.
• err-disable —The port is unable to provide power to the connected device that is configured in static mode.
• faulty —The port failed diagnostics tests.

To view the operational status for an interface, use the show power inline command.

This example shows how to display the operational status for all interfaces on module 3:

This example shows how to display the operational status for Fast Ethernet interface 4/1:

Displaying all PoE Detection and Removal Events

A Catalyst 4500 series switch can display all PoE detection and removal events.

To enable PoE event logging, you use the power inline logging global command:

Displaying the PoE Consumed by a Module

A Catalyst 4500 series switch can measure the actual PoE consumption for an 802.3af-compliant PoE module. You can observe this consumption by using show power module and show power detail commands. For all PoE calculations, presume that the PoE consumption on the WS-X4148-RJ45V module equals its administrative PoE.

The 802.3af-compliant PoE modules can consume up to 20 W of PoE to power FPGAs and other hardware components on the module. To ensure that the system has sufficient power for the PDs connected to the switch, add at least 20 W to your PoE requirements for each 802.3af-compliant PoE module.

The following example uses the show power module command to display the PoE consumption for an 802.3af-compliant module:

The Inline Power Oper column displays the amount of PoE consumed by the powered devices that are attached to the module, in addition to the PoE consumed by the FPGAs and other hardware components on the module.

The Inline Power Admin column displays only the amount of PoE allocated by the powered devices attached to the module.

Note The operating PoE consumption for an 802.3af-compliant module can be non-zero, even when no powered devices are attached to the module, because of the PoE consumed by FPGAs and other hardware components on the module. In addition, the operating PoE can vary because of fluctuations in the PoE consumed by the hardware components.

The following example uses the show power detail and show power inline commands to display the PoE consumption for an 802.3af-compliant module:

PoE Policing and Monitoring

Note This functionality is supported on the WS-X4548-RJ45V+, WS-X4648-RJ45V-E, and WS-X4648-RJ45V+E line cards.

PoE policing protects a switch from faulty inline powered devices that may draw more current than they were designed for. When a device is connected to a port, a line card detects the type of device connected and allocates the appropriate amount of power. It sets a PoE policing threshold to a value 5 percent greater than the allocated power. If the device consumes more power than specified by the policing threshold for a more than 1 second, the port shuts down. Depending on the policing action configured, the port may then be error-disabled, or a message might be logged to the console and the port restarted.

PoE monitoring lets you display the true power consumption of inline powered devices attached to the switch, allowing you determine your actual power consumption.

This section includes these topics:

• PoE Policing Modes
• Configuring Power Policing on an Interface
• Displaying Power Policing on an Interface
• Configuring Errdisable Recovery

PoE Policing Modes

PoE policing comprises two modes, which determine the action to take on the interface after a port shuts down because of an inline-power policing violation:

• Logging — An error message is logged to the console and the interface restarts; the device powers up.
• Errdisable (Default) — In addition to logging an error message to the console, the interface is placed in an errdisable state so that the device attached to the port does not receive inline-power until you restart the port or configure an errdisable autorecovery mechanism.

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Note After an inline-power policing violation occurs and the port shuts down, PoE policing automatically turns on again when the port restarts. If the connected device exceeds its allocated power again, the port once again shuts down.

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Configuring Errdisable Recovery

By default, errdisable auto recovery for inline-power is disabled; when an interface is placed in an errdisable state because of an inline-power policing violation, it remains in that state. You must enter shut and then no shut on the affected interface to revive it.

The errdisable autorecovery mechanism allows you to configure a timer for errdisable recovery so that when an interface enters errdisable state (after the timer expires), the interface returns from the errdisable state.

errdisable detection

By default, errdisable detection for inline-power is enabled, as the following example illustrates:

Switch# show errdisable detect

ErrDisable Reason Detection Mode

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inline-power Enabled port

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Note If detection is disabled (through the errdisable detect cause inline-power command), the port is not placed in errdisable state when it exceeds its power policing threshold.

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errdisable recovery

By default, errdisable recovery for inline-power is disabled. To enable errdisable recovery, enter the errdisable detect cause line-power command:

Switch# config terminal

Enter configuration commands, one per line. End with CNTL/Z.

Switch(config)# errdisable detect cause inline-power

Switch(config)# end

Switch# show errdisable recovery

ErrDisable Reason Timer Status

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inline-power Enabled

Enhanced Power PoE Support on the E-Series Chassis

The WS-X4648-RJ45V-E, WS-X4648-RJ45V+E, and WS-X4548-RJ45V+ switching modules support IEEE 802.3af PoE as well as the Cisco proprietary Inline Power standard. With
Cisco IOS Release 12.2(44)SG, the WS-X4648-RJ45V+E line card can also support the IEEE 802.3at standard with up to 30 W available per-port. The WS-X4648-RJ45V-E line card also supports up to 20 W. The WS-X4548-RJ45V+ switching module is supported with Cisco IOS Release 12.2(50)SG and can provide up to 30 W of inline power per-port.

For these switching modules, the valid milliwatt ranges for the power inline command have been increased appropriately for the module, as the following table illustrates:

The default power inline configurations usually are sifficient; no additional configuration is required even for high power-consumption Cisco powered devices (for example, a Cisco AP1250 Wireless Access Point). When a high-power consumption device is attached to a port on a WS-X4648-RJ45V-E or WS-X4648-RJ45V+E line card, the switch and device negotiate power using CDP packets to automatically determine the extended amount of power needed by the device.

Depending on the deployment requirements and design, you specify a specific configuration with the power inline command.

The following example shows how to pre-allocate PoE allocation to 16500 mW for Gi 2/1, regardless of what is mandated either by the 802.3af class of the discovered device or by any CDP packet that is received from the powered device: