Juniper EX8208 Hardware Manual page 127

= N + N
= 3 + 3
= 6
5. If the switch has PoE line cards:
a. Add the configured PoE power budgets for PoE line cards to the total power requirement value
that you calculated in step 2.
b. Calculate the number of power supplies needed to meet the new total power requirement by dividing
the total power requirement by the output wattage of one power supply and then rounding up.
c. Compare this result to the N+1 or N+N value you calculated in step 4. Use the greater of the two
values to determine how many power supplies you require.
NOTE: We recommend that you maintain N +1 or N+N power supplies in your switch at all
times. Replace failed power supplies immediately to prevent unexpected failures.
Power management raises a minor alarm if the number of online power supplies in your switch
is less than the number required to maintain the configured power redundancy (N+1 in Junos
OS Release 10.1 or earlier; N+1 or N+N in Junos OS Release 10.2 or later). If the problem is not
corrected in 5 minutes, a major alarm is issued.
Power management raises a major alarm if the number of online power supplies in your switch
is less than N power supplies. If your switch is running Junos OS Release 10.1 or earlier, all line
cards are powered off. If your switch is running Junos OS Release 10.2 or later, power
management provides power to line cards in priority order until power is exhausted. The remaining
line cards are powered off.
If a new line card is installed in an operational switch, power management does not power on
the line card if the increased power demand exceeds the total available power, including redundant
power. If redundant power is used to power on the line card, a minor alarm is raised, which
becomes a major alarm in 5 minutes if the condition is not corrected.
Power management does not take into account PoE budget allocations when raising alarms to
indicate that N, N+1, or N+N requirements are not being met.
SEE ALSO
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