Brocade FastIron Ethernet Switch Administration Guide - Manual (Page 265)

measuring the current consumption of the PD. Depending on the measured current, the appropriate
class is assigned to the PD. PDs that do not support classification are assigned a class of 0 (zero). The
table below shows the different power classes and their respective power consumption needs.
Power classes for PDs TABLE 37
Class Usage
Power (watts) from Power Sourcing Device
Standard PoE PoE+
0 default 15.4 15.4
1 optional 4 4
2 optional 7 7
3 optional 15.4 15.4
4 optional NA 30
Power specifications
The 802.3af (PoE) standard limits power to 15.4 watts (44 to 50 volts) from the power sourcing device,
in compliance with safety standards and existing wiring limitations. Though limited by the 802.3af
standard, 15.4 watts of power was ample for most PDs, which consumed an average of 5 to 12 watts of
power (IP phones, wireless LAN access points, and network surveillance cameras each consume an
average of 3.5 to 9 watts of power). The newer 802.3at (PoE+) standard nearly doubles the power,
providing 30 watts (52 or 54 volts) from the power sourcing device.
The PoE power supply provides power to the PoE circuitry block, and ultimately to PoE power-
consuming devices. The number of PoE power-consuming devices that one PoE power supply can
support depends on the number of watts required by each power-consuming device. Each PoE power
supply can provide either 1080 or 2380 watts of power, and each PoE port supports a maximum of
either 15.4 or 30 watts of power per power-consuming device. For example, if each PoE power-
consuming device attached to a FastIron PoE device consumes 10 watts of power, one 1080 watt
power supply will power up to 108 PoE ports. You can install a second PoE power supply for additional
PoE power. Power supply specifications are covered in the Brocade FastIron X Series Chassis
Hardware Installation Guide and in the Brocade FastIron CX Hardware Installation Guide.
By default, FastIron device pre-allocates power of 15.4 or 30 watts for a physically operational PoE or
PoE+ configured port respectively. However in an ICX 6450-C12 device that is operational without
direct power supply and has pass-through power, there is no pre-allocation. Instead, power is allocated
only when a powered device is connected to the port. By default, the amount of power allocated
depends on the power class of the powered device.
Dynamic upgrade of PoE power supplies
NOTE
This section applies to the SX 800 and SX 1600 chassis with PoE power supplies.
PoE+ requires higher power levels than standard PoE. In a chassis running software release 07.2.00 or
higher, POE power supplies (SX-ACPWR-POE) are upgraded dynamically to 52 or 54 volts, depending
on the maximum operating voltage the power supplies are capable of. The preferred voltage mode for
PoE+ is 54 volts.
Dynamic upgrade of PoE power supplies
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