Q. Can you support 15.4 W on all 48 ports?

A. The Cisco Catalyst 3750/3560 PoE switches have 370 W available for Power over Ethernet, which is shared by all 48 ports. The 48 port POE switches have the ability to support all 48 ports at 7.5 watts or 24 ports at 15.4 W simultaneously and any given port could be configured up to maximum of 15.4 watts to support 802.3af classification.

Q. What is the "Power Inline Consumption Feature" and how does it work?

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

Following are two scenarios where the Consumption 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 (e.g., the Siemens IP phone requires 5 W). Without the "Power Inline Consumption" feature, customers could only deploy 24 of these devices, whereas customers can deploy up to 48 of these devices using the Power Inline Consumption command to configure the power requirements on the switchports.

• 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 worst case. If the `Consumption' CLI configured ports supporting this phone to 8 W, a 3750-48PS could power 46 phones instead of 24, and do it safely.

A customer who misconfigures the switch (by over-subscribing the power supply) may reduce its reliability or damage the switch. If the power supply is over-subscribed by up to about 20%, the switch will continue to operate but its reliability may be reduced. Above about 20%, the short-circuit protection circuitry will trigger and shut the switch down.