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Complete Software Guide for Junos
PoE Power Management
3532
®
OS for EX Series Ethernet Switches, Release 10.4
Switches that have PoE ports have a PoE controller that keeps track of the PoE power
consumption on the switch and allocates power to the PoE ports. The following factors
determine how the PoE controller allocates power to the PoE ports:
PoE Power Budget on page 3532
Power Management Mode on page 3532
PoE Interface Power Priority on page 3533
PoE Power Budget
The PoE controller allocates power to the PoE ports from a set PoE power budget. The
PoE power budget varies according to switch model and, for switches that support power
supplies of different capacities, the capacity of the installed power supply. For example,
a Juniper Networks EX3200 Ethernet Switch with a 320 W power supply has a PoE power
budget of 130 W, while with a 600 W power supply it has a PoE power budget of 410 W.
In switches that support power supplies of different capacities, if you change your existing
power supply to a lower-capacity power supply, the PoE power budget might no longer
be sufficient to power all the PoE ports on the switch. If your switch supports redundant
power supplies and you have installed power supplies of different capacities, the PoE
power budget is based on the wattage of the lower-capacity power supply. The number
of PoE ports on the switch cannot be increased by installing a larger power supply.
You can display the PoE power budget for your switch by using the
command.
Power Management Mode
EX Series switches support two power management modes: class and static. The mode
you configure for your switch determines how the maximum power for a PoE interface
is derived and how power is allocated to the PoE interfaces:
Class mode—In this mode, the maximum power for an interface is determined by the
class of connected powered device. Table 477 on page 3532 lists the classes of powered
devices and associated power levels.
Table 477: Class of Powered Device and Power Levels
Standard
Class
IEEE 802.3af (PoE)
0
and IEEE 802.3at
(PoE+)
1
2
3
IEEE 802.3at (PoE+)
4
Maximum Power
Power Range of Powered
Delivered by PoE Port
Device
15.4 W
0.44 through 12.95 W
4.0 W
0.44 through 3.84 W
7.0 W
3.84 through 6.49 W
15.4 W
6.49 through 12.95 W
30.0 W
12.95 through 25.5 W
Copyright © 2010, Juniper Networks, Inc.
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