Poe Budget; Port Prioritization - Allied Telesis AT-IE300-12GP Installation Manual

Chapter 1: Overview

PoE Budget

Port
Prioritization
30
Non-PoE devices can be connected to any of the twisted pair ports

on the switch. Ports connected to network nodes that are not PDs
(that is, devices that receive power from another power source)
function as regular Ethernet ports, without PoE. The PoE feature
remains enabled on the ports but no power is delivered to the
devices.
The AT-IE300-12GP Switch has a PoE budget. This is the total wattage
the switch has available for the powered devices on its ports. The
maximum possible budget is 240W. The PoE budget can never be more
than that, but it can be less, depending on the DC power supply.
The number of powered devices the switch can support at one time will
depend on the switch's PoE budget and the wattage requirements of the
powered devices. As long as the total wattage requirements of the
powered devices is less than the budget of the switch, the switch can
supply power to all the devices. If the total wattage requirements exceed
the PoE budget, the switch will deny power to one or more devices using a
mechanism referred to as port prioritization.
To determine whether the wattage requirements of the PoE devices you
plan to connect to the switch exceed its budget, refer to their
documentation for their power requirements and add the requirements
together. The switch should be able to power all the devices
simultaneously as long as the total is below its PoE budget. If the total
exceeds the available power budget, you should consider reducing the
number of PoE devices so that all the devices receive power. Otherwise,
the switch powers a subset of the devices, based on port prioritization.
The switch can handle different power requirements on different ports.
This enables you to connect different classes of PoE equipment to the
ports on the switch.
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