Power Budget; Port Prioritization - Allied Telesis AT-x550-18XTQ Installation Manual

Power Budget

The AT-x550-18XSPQm Switch has a DC power budget of 240W. This is
the total maximum amount of power that the switch can supply to powered
devices on the eight PoE+ twisted pair ports. Under normal operating
conditions this power budget enables the switch to support eight Class 4
devices with the maximum 25.5W on all eight PoE+ ports, simultaneously.
Port
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
Prioritization
called port prioritization. You can 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:
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 at the Critical level are receiving power. If there is
not enough power to support all 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.
Table 10. IEEE Powered Device Classes (Continued)
Class Output from a Switch
2 7.0W
3 15.4W
4 30.0W

Critical

High

Low
x550 Series Installation Guide for Virtual Chassis Stacking
Maximum Power
Port
PD Power Range
3.84W to 6.49W
6.49W to 12.95W
12.95W to 25.5W
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