Juniper EX4300 Series

N+N Redundancy Conguraon of DC Power Supplies
You can congure your switch for N + N redundancy, in which N power supplies can be removed or fail
and the remaining N power supplies connue to supply power for the switch without interrupon.
You can congure the power management soware to manage switch power for N + N redundancy.
When you congure power management for N + N redundancy, half of the total power available ( N ) is
held as reserve power while the other half ( N ) is available for immediate consumpon. If the switch
conguraon changes and requires addional power, then addional power is drawn from the reserve
power, and the switch no longer has N + N power supply redundancy. This condion raises a minor alarm.
If the condion is not corrected within 5 minutes, then a major alarm is issued.
For more informaon about how power management allocates power to chassis components when
power is insucient, see Understanding Power Management on EX Series Switches.
Depending on the power supplies installed in the switch, you can determine the system power budget.
• If one power supply is installed in the switch:
• System power budget = Output waage of the installed power supply (PSU(W))
• Backup power available = 0 W
A minor alarm is raised as switch has no
N + N power supply redundancy.
• If two power supplies are installed in the switch:
• System power budget = (Output waage of one power supply) – (5% of the output waage of
one power supply)
System power budget = PSU(W) – (0.05 x PSU(W))
• Backup power available = (Output waage of one power supply) – (5% of the output waage of
one power supply)
System power budget = PSU(W) – (0.05 x PSU(W))
Table 50 on page 118 lists the N + N power calculaon for EX4300 switches that use 550 W DC power
supplies.
NOTE: The DC power supply in the switch does not support Power over Ethernet (PoE); you can
use either an external power injector or an AC power supply to supply power to PoE devices that
you connect to the switch. 32-port EX4300 switches does not support Power over Ethernet
(PoE).
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