Power over Ethernet
PoE on the Switch
Cisco 220 Series Smart Switches Administration Guide Release 1.1.0.x 124
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CAUTION Consider the following when connecting switches capable of supplying PoE:
The PoE models of the switches are Power Sourcing Equipments (PSEs) that are
capable of supplying DC power to attaching Powered Devices (PDs). These
devices include VoIP phones, IP cameras, and wireless access points. The PoE
switches can detect and supply power to pre-standard legacy PoE Powered
Devices. Due to the support of legacy PoE, it is possible that a PoE switch acting as
a PSE may mistakenly detect and supply power to an attaching PSE, including other
PoE switches, as a legacy PD.
Even though PoE switches are PSEs, and as such should be powered by AC, they
could be powered up as a legacy PD by another PSE due to false detection. When
this happens, the PoE switch may not operate properly and may not be able to
properly supply power to its attaching PDs.
To prevent false detection, you should disable PoE on the ports on the PoE switches
that are used to connect to PSEs. You should also first power up a PSE device
before connecting it to a PoE switch. When a device is being falsely detected as a
PD, you should disconnect the device from the PoE port and power recycle the
device with AC power before reconnecting its PoE ports.
PoE on the Switch
A PoE switch is Power Sourcing Equipment (PSE) that delivers electrical power to
the connected powered devices (PD) over existing copper cables without
interfering with the network traffic, updating the physical network or modifying the
network infrastructure.
PoE Features
PoE provides the following features:
• Eliminates the need to run 110/220 V AC power to all devices on a wired
LAN.
• Removes the necessity for placing all network devices next to power
sources.
• Eliminates the need to deploy double cabling systems in an enterprise
significantly decreasing installation costs.
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