Allied Telesis x310 Series - Manual (Page 29)

x310 Series Installation Guide for Stand-alone Switches
29
Port
Prioritization
If the power requirements of the powered devices exceed the switch’s
power budget, the switch denies 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 assigned to the other priority levels receive power only if all the
Critical ports are receiving power. Ports that are connected to your most
critical powered devices should be assigned to this level. If there is not
enough power to support all the ports set to the Critical priority level, power
is provided to the ports 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. If you limit 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 have sufficient
power to support the critical devices even if it has only one functional
power supply.