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

13-7
Planning and Implementation for the HP 5400zl/8200zl Switches
Introduction
Switch Power Supply Shelf will not supply any 12V (system power) to any zl
switch, since the switch is provided with 12V redundancy when more than one
power supply is installed in the chassis.
Configuring PoE Redundancy
When considering redundant power, also consider the power source for the
power supplies. Each power supply should be connected to a separate power
source circuit in order to supply complete redundancy. Should one circuit fail,
it would then be possible for the other circuit to continue supplying power to
the second power supply in the switch, keeping the switch running.
When PoE redundancy is enabled, PoE redundancy occurs automatically. The
switch keeps track of power use and won’t supply PoE power to additional
PoE devices trying to connect if that results in the switch not having enough
power in reserve for redundancy if one of the power supplies should fail. There
are three configurable redundancy methods:
■ No PoE redundancy enforcement (default). All available power can be
allocated.
■ Full redundancy: half of the totally available PoE power can be allocated
and half is held in reserve for redundancy. If power supplies with different
ratings are used, the highest-rated power supply is held in reserve to
ensure full redundancy.
■ N+1. One of the power supplies is held in reserve for redundancy. If a
single power supply fails, no powered devices are shut down. If power
supplies with different ratings are used, the highest-rated power supply is
held in reserve to ensure full redundancy.
Note When changing from one method to another, always check the current level
of PoE usage before implementing the change. The change could cause
existing connection to lose PoE power.
When considering redundant power, also consider the power source for the
power supplies. Each power supply should be connected to a separate power
source circuit in order to supply complete redundancy. Should one circuit fail,
it would then be possible for the other circuit to continue supplying power to
the second power supply in the switch, keeping the switch running.