HP Power over Ethernet (PoE/PoE+) Planning and Implementation Guide

9-5
Planning and Implementation for the HP 2920-PoE+ Switches
Planning the PoE Configuration
PoE/PoE+ Allocation Using LLDP Information
A PoE port can automatically configure certain PoE+ link partner devices if
the device supports advertising of its PoE needs.
By enabling PoE LLDP detection, available information about the power
requirements of the PD may be used by the switch to configure the power
allocation. The initial configuration for PoE ports may change if more accurate
configuration information is provided by way of LLDP.
For more configuration information, refer to the Management and
Configuration Guide for your switch at www.hp.com/networking/support. Auto
search on “2920”, select your switch model from the list, and click Display
selected. Then click on the links that have “Manuals” in them to get to the web
page that lists the available manuals.
Planning the PoE Configuration
This section assists you in building a PoE or PoE+ configuration. Using the
following examples you can plan, build, and connect PoE and PoE+ devices
quickly and easily.
There are two configurations:
■ HP 2920-24G-PoE+ Switch
■ HP 2920-48G-PoE+ Switch
Each example shows a complete configuration. A table shows the PoE/PoE+
power available to connected PoE and PoE+ devices.
Once you have selected your specific configuration and the PoE/PoE+ power
provided, you then add up the maximum amount of power each of your IEEE
802.3af-compliant (PoE) and IEEE 802.3at-compliant (PoE+) devices require
(use maximum power in watts, usually found on a product’s data sheet).
Adjust this total maximum power figure by adding 16% to account for possible
line loss. This value must be less than the maximum power available shown
in the table for your configuration.
These switches use a single internal power supply which provides output
voltages for both switch and PoE functionality. One supply voltage provides
power for the switch functionality while the isolated voltage provides power
for the PoE functionality. If either voltage fails, the entire power supply shuts
down disconnecting all switch and PoE connections.