Allied Telesis AT-9000 Series - Manual (Page 157)

AlliedWare Plus Version 2.1.8 Management Software Web Interface User’s Guide
157
Power Budget Power budget is the maximum amount of power that the PoE switch can
provide at one time to the connected PDs. The AT-9000/12POE switch
has a power budget of 125 watts. The AT-9000/28POE switch has a
power budget of 370 watts.
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 port prioritization 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 Critical
ports are receiving power. Ports that are connected to the most critical
powered devices should be assigned to this level. If there is not enough
power to support all ports set to the Critical priority level, power is provided
to the ports based on the port number, in ascending order.
The High level is the second highest level. Ports set to this level receive
power only if all ports set to the Critical level are already receiving power. If
there is not enough power to support all ports set to the High priority level,
power is provided to the ports based on the 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 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 ports set to the Low priority level, power is provided to
the ports based on the 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
have sufficient power to support the critical devices, even if it has only one
functional power supply.