Dell PowerConnect J-8216 Software Guide for JUNOS version 10.3 - Page 375

Chapter 18: Power Management Overview Power Priority of Line Cards Power management powers line cards on or off based on the power priority of the slots they occupy: • When a switch powers on, power management provides power to the line cards in the order of their slot priority, with line cards in high priority slots receiving power first. Thus if available power (including redundant power) is exhausted before all line cards receive power, higher priority cards are powered on while lower priority cards remain powered off. • If the switch starts receiving insufficient power because of power supply failure or some other problem, power management powers off the line cards in reverse-priority order until power (including redundant power) is sufficient for the remaining cards. Thus higher priority line cards are more likely to retain power in power shortage conditions than are lower priority line cards. • Power management responds to changes in power availability and line card operating status by powering line cards on or off as appropriate. For example, if you add a power supply, lower priority cards that were powered off due to insufficient power are powered on in priority order. If you take a line card offline, power management no longer allocates power to it. If power to the switch is insufficient when you take a line card offline, power management allocates the freed power to a lower priority card that was offline due to lack of power and brings it online. Restarting a line card, however, does not affect the power allocated to it. Thus when power is insufficient, restarting a line card does not change its operating status or the operating status of other line cards. NOTE: Because power management does not allocate power to an offline line card, a line card that has been taken offline in a J-EX8200 switch is not automatically brought online when you commit a configuration. You must explicitly bring the line card online with the request chassis fpc slot slot-number online command. This behavior differs from other platforms running the 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. 303