Power Over Ethernet (Poe) - Allied Telesis SwitchBlade x3100 Series Manual

Definitions

3. Power over Ethernet (PoE)

3.1 Introduction
The SBx3112 switch provides Power over Ethernet (PoE) capability with the GE24POE card. The GE24POE
card allows up to 24 devices (one per port) to receive power from the Ethernet faceplate connection. With PoE
technology, a supported Ethernet-based terminal (known as a Powered Device or PD) can receive up to 30
watts of power over the same Ethernet cable as data. Examples of PDs include IP phones, wireless access
points, and IP cameras.
Power can be carried over Ethernet cables in one of two ways:
Mode A uses the data pairs 1-2 and 3-6.
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Mode B uses the spare pairs 4-5 and 7-8, which are unused in 10/100BASE-T. The power applied allows data
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flow to be maintained regardless of power status.
The IEEE PoE Power Standard 802.3af only allows one set of wires to be used per device. Mode B is
Note:
not supported on the GE24POE card.
The IEEE 802.3af standard defines support for devices up to 15.4 watts. (A newer standard IEEE 802.3at extends
the power range to 25.5 watts.)
3.1.1 Definitions
The following terms are used throughout this chapter:
PoE (Power over Ethernet) - the 802.3af PoE feature that allows power to be carried over the same Ether-
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net infrastructure as data
PSE (Power Sourcing Equipment) - the source, such as an Ethernet switch, that is responsible for supplying
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power to one or more devices by Ethernet cable
PD (Powered Device) - the device receiving power by Ethernet cable from a PSE
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PoE PSU (Power Supply Unit) - one of the devices providing power to the shelf for use in powering PDs
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Allocated power - the amount of power the PoE manager on the Central Fabric Control (CFC) card has
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given to a PoE line card to use; it may be greater or less than the amount of power the card has requested.
Requested power - the amount of power a port has requested for PoE. It is equal to the port's user power
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limit (if set) or based on the determined classification of the discovered PD. Ports with no discovered PD are
not requesting power. The card's requested power is the sum of all ports.
Actual power - the actual, instantaneous, power draw of a port or card as measured by the PSE.
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Software Reference for SwitchBlade x3100 Series Switches (Power over Ethernet (PoE))
Introduction
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