Stack Installation Guide for 8100S Series Switches
37
PortPrioritizationIf the power requirements of the powered devices exceed the switch’s
power budget, the switch will deny power to some ports based on a
system called port prioritization. You may use this mechanism to ensure
that powered devices critical to the operations of your network are given
preferential treatment by the switch in the distribution of power should the
demands of the devices exceed the available capacity.
There are three priority levels:
Critical
High
Low
Ports set to the Critical level, the highest priority level, are guaranteed
power before any of the ports assigned to the other two priority levels.
Ports that are connected to your most critical powered devices should be
assigned to this level. Ports assigned to the other priority levels receive
power only if all the critical ports are receiving power. If there is not enough
power to support all the ports set to the Critical priority level, power is
distributed based on port number, in ascending order.
The High level is the second highest level. Ports set to this level receive
power only if all the ports set to the Critical level are already receiving
power. If there is not enough power to support all of the ports set to the
High priority level, power is provided to the ports based on port number, in
ascending order.
The lowest priority level is Low. This is the default setting. Ports set to this
level only receive power if all of the ports assigned to the other two levels
are already receiving power. As with the other levels, if there is not enough
power to support all of the ports set to the Low priority level, power is
provided to the ports based on port number, in ascending order.
Power allocation is dynamic. Ports supplying power to powered devices
may cease power transmission if the switch’s power budget is at maximum
usage and new powered devices, connected to ports with higher priorities,
become active.
You can use port prioritization on dual power supply PoE switches to
protect your important networking devices from loss of power should one
of the power supplies fail or lose power. By limiting the power
requirements of the critical devices connected to a switch to less than 185
watts, the PoE power provided by a single power supply, a switch will be
able to continue to power the critical devices even if it has only one
functional power supply.