PoE/PoE+ Planning and Implementation Guide 2011-09

12-7
Planning and Implementation for the E3800 Switches
Planning Your PoE or PoE+ Configuration
By load balancing in this manner there could be a specified number of devices
on one bank of ports, say 1-24, and another specified number of devices on
the other bank of ports, 25-48 powered at an average of 30 watts each.
Both of these examples use maximum device wattage. If however, devices
using lower wattages are connected there could be more devices connected
to the switch than shown in these examples. Each environment will be
different.
There is a CLI command available, the THRESHOLD command. It has an
informational only result. This command sets a threshold, by percent, to
inform you the switch is now using more than a certain percentage of PoE
power. For example if the threshold is set at 50%, the switch will issue an
information message informing you the switch has exceeded the threshold
when 51% of available PoE power is being used. Also see page 13-12 for an
example. For more information on the threshold command, Refer to the
Management and Configuration Guide for your switch at
www.hp.com/networking/support.
The table in this example configuration contains entries that show the PoE+
power available for the E3800-48G-PoE+-4SFP+ or E3800-48G-PoE+-4XG
Switch when two power supplies are installed.
Figure 12-4. Example of E3800-48G-PoE+-4SFP+ or E3800-48G-PoE+-4XG Switch
with two power supplies installed
The switch can supply full redundant power from the second power supply
should one of the power supplies fail, however PoE/PoE+ power will be
reduced until the failed power supply is replaced.
The lowest loaded bank of ports (1-24 or 25-48) has 22 watts reserved. That
power is available for use by the two highest priority ports in the bank, (in a
default configuration ports 1 and 2, or 25 and 26).
36 ports can supply up to 30 watts
of PoE+ power