Configuration Guide User guide

FastIron Configuration Guide 663
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Power over Ethernet overview
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.
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.
For safety reasons, all PoE power supplies installed in the chassis must operate at the same
voltage mode, either 52 volts or 54 volts. The system will select the voltage mode of the power
supply with the lowest supported voltage as the voltage mode for all PoE power supplies installed in
the chassis. For example, in a FSX 800 chassis with one 52-volt capable PoE power supply and one
54-volt capable PoE power supply, both power supplies will be configured dynamically to operate at
52 volts.
PoE+ voltage selection occurs during each of the following events:
• When the device is powered ON or is rebooted
TABLE 122 Power classes for PDs
Class Usage Power (watts) from Power Sourcing Device
Standard PoE PoE+
0default15.430
1optional4 4
2optional7 7
3 optional 15.4 15.4
4optional15.430