How to configure the Power Inline Consumption feature in Cisco Catalyst 3560 and 3750 Series switches


Wed, 07/22/2009 - 19:49
Jun 22nd, 2009


The Power Inline Consumption feature on the Cisco Catalyst 3560 and 3750 Series Power over Ethernet (PoE) products allows the network administrator to configure the actual power requirements of the powered device (PD). This feature allows the administrator to override the powered device classification setting.This is a feature that was requested by many large Enterprise customers and is supported beginning with release 12.2(25)SEC.

These are two scenarios in which the Consumption Command Line Interface (CLI) can be used to manually configure the PoE allocation much more efficiently than the automatic algorithms:

Currently, the Cisco Catalyst 3750 Series budgets 15.4 W for Class 0 PDs. However, some of these PDs require a maximum of much less than 15.4 W (for example, the Siemens IP phone requires 5 W). Without the Power Inline Consumption feature, customers could only deploy 24 of these devices. Customers can deploy up to 48 of these devices with the power inline consumption command for configuration of switchport power requirements.

Class 3 PDs are allocated 15.4W normally. Some IEEE Class 3 PDs (8-15 W range) use considerably less than 15.4 W maximum. An example is the Avaya 2620SW, which uses 8W in the worst case scenario. If the Consumption CLI configured ports that support this phone to 8 W, a 3750-48PS could safely power 46 phones instead of 24.

Note: Any misconfiguration on the switch (an over-subscription of the power supply) can reduce its reliability or damage the switch. If the power supply is over-subscribed by up to about 20 percent, the switch continues to operate but its reliability can be reduced. Above about 20 percent, the short-circuit protection circuitry triggers and shuts the switch down.

Issue the power inline consumption global or interface configuration command on the switch stack or on a standalone switch to override the amount of power specified by the IEEE classification for the device. Then, specify the wattage used by each powered device.

For more information, refer to Cisco Catalyst 3750 Q&A.


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