Juniper JUNOS OS 10.3 - SOFTWARE Manual page 476

Complete Software Guide for Junos
Power Supply Redundancy
380
®
OS for EX Series Ethernet Switches, Release 10.3
NOTE: Because power management does not allocate power to an offline
line card, a line card that has been taken offline in an EX8200 switch is not
automatically brought online when you commit a configuration. You must
explicitly bring the line card online with the
slot-number online
running Junos operating system (Junos OS), which automatically bring an
offline FPC online when you commit a configuration.
The actual power priority of a slot is determined first by the slot's assigned priority and
second by the slot's number. If more than one slot has the same assigned priority, power
priority is determined by slot number, with the lowest-numbered slots receiving power
first.
By default, all slots are assigned the lowest priority. You can assign a priority to a slot
using the CLI. If you do not explicitly assign priorities to slots, the slots receive power in
ascending order of slot numbers.
Because the purpose of power management is to ensure minimal system disruption
when power is insufficient, slot power priority does not always determine which line cards
receive power. In some cases, power management might provide power to a lower priority
line card rather than a higher priority line card. For example:
If power is insufficient for a line card in a higher priority slot but is sufficient for a line
card in a lower priority slot, the lower priority slot receives the power. For example, if
an 8-port SFP+ line card requiring 450 W is in a higher priority slot than a 48-port SFP
line card requiring 330 W, the 48-port SFP line card receives the power if there is more
than 330 W but less than 450 W available.
In an operating switch that has insufficient power, power management does not power
off operating line cards to provide power to a newly inserted line card or a line card
that is brought online after being offline, even if the line card has a higher priority than
the currently operating line cards.
However, if you restart the switch, power management reruns the current power budget
policy and powers line cards on or off based on their priority. As a result, line cards
receive power strictly by priority order and previously operating line cards might no
longer receive power.
If you change the assigned power priority of line cards when there is insufficient power
for all the line cards, power management does not power down line cards that had
been receiving power because they are now a lower priority.
By default, power management in EX8200 switches is configured to manage the power
supplies for N+1 redundancy, in which one power supply is held in reserve for backup if
one of the other power supplies is removed or fails.
request chassis fpc slot
command. This behavior differs from other platforms
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