When configuring PoE, go to these sections
for information you are interested in:
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PoE
Overview
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PoE
Configuration Task List
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Configuring
the PoE Interface
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Configuring
PD Power Management
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Configuring
a Power Alarm Threshold for the PSE
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Upgrading
PSE Processing Software Online
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Configuring
a PD Disconnection Detection Mode
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Enabling
the PSE to Detect Nonstandard PDs
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Displaying
and Maintaining PoE
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PoE
Configuration Example
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Troubleshooting
PoE
1.1.1 Introduction
to PoE
Power over Ethernet (PoE) means that power
sourcing equipment (PSE) supplies power to powered devices (PD) such as IP
telephone, wireless LAN access point, and web camera from Ethernet interfaces
through twisted pair cables.
I. Advantages
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Reliable: Power is supplied in a centralized way
so that it is very convenient to provide a backup power supply.
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Easy to connect: A network terminal requires
only one Ethernet cable, but no external power supply.
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Standard: In compliance with IEEE 802.3af, and a
globally uniform power interface is adopted.
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Promising: It can be applied to IP telephones,
wireless LAN access points, portable chargers, card readers, web cameras, and
data collectors.
II. Composition
A PoE system consists of PoE power, PSE,
and PD.
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PoE power
The whole PoE system is powered by the PoE
power, which includes external PoE power and internal PoE power.
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PSE
PSE is a card or subcard. PSE manages its
own PoE interfaces independently. PSE examines the Ethernet cables connected to
PoE interfaces, searches for the devices, classifies them, and supplies power
to them. When detecting that a PD is unplugged, the PSE stops supplying power
to the PD.
An Ethernet interface with the PoE
capability is called PoE interface. Currently, a PoE interface can be an FE or
GE interface.
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PD
A PD is a device accepting power from the
PSE. There are standard PDs and nonstandard PDs. A standard PD refers to the
one that complies with IEEE 802.3af. The PD that is being powered by the PSE
can be connected to other power supply units for redundancy backup.
The protocol specification related to PoE
is IEEE 802.3af.
Complete these tasks to configure PoE:
1.3 Configuring the PoE Interface
You can configure a PoE interface in either
of the following two ways:
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Adopting the command line.
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Configuring a PoE configuration file and
applying the file to the specified PoE interface(s).
Usually, you can adopt the command line to
configure a single PoE interface, and adopt a PoE configuration file to
configure multiple PoE interfaces at the same time.
Caution:
You can adopt either mode to configure, modify, or delete a PoE
configuration parameter under the same PoE interface.
The PSE supplies power for a PoE interface
in the following two modes:
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For a device with only signal cables, power is
supplied over signal cables.
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For a device with spare cables and signal cables,
power can be supplied over spare cables or signal cables.
S5500-SI series
Ethernet switches do not support power over spare cables. In this case, if the
PD only supports power over spare cables, you have to change the order of the lines
in the twisted pair cable to supply power to the PD.
1.3.1 Configuring a PoE Interface through the Command Line
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Enter PoE interface view
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interface interface-type interface-number
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—
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Enable PoE
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poe enable
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Required
Disabled by default.
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Configure the maximum power for the PoE
interface
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poe max-power max-power
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Optional
15,400 milliwatts by default.
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Configure the PoE mode for the PoE
interface
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poe mode signal
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Optional
signal
(power over signal cables) by default.
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Configure a description for the PD
connected to the PoE interface
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poe pd-description string
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Optional
By default, no description for the PD
connected to the PoE interface is available.
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A PoE configuration file is used to
configure at the same time multiple PoE interfaces with the same attributes to
simplify operations. This configuration method is a supplement to the command
line configuration.
Commands in a PoE configuration file are
called configurations.
Follow these steps to configure PoE
interfaces through a PoE configuration file:
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Create a PoE configuration file and enter
PoE configuration file view
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poe-profile profile-name [ index ]
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Required
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Enable PoE for the PoE interface
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poe enable
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Required
Disabled by default.
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Configure the maximum power for the PoE
interface
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poe max-power max-power
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Optional
15,400 milliwatts by default.
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Configure the PoE mode for the PoE
interface
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poe mode signal
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Optional
signal (power
over signal cables) by default.
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Return to system view
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quit
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—
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Apply the PoE configuration file to the
PoE interface(s)
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Apply the PoE configuration file to one
or more PoE interfaces
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apply poe-profile { index
index | name profile-name } interface interface-range
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Use either approach
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Apply the PoE configuration file to the
current PoE interface in PoE interface view
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interface interface-type interface-number
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apply poe-profile { index
index | name profile-name }
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Caution:
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After a PoE configuration file is applied to a
PoE interface, other PoE configuration files can not take effect on this PoE
interface.
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If a PoE configuration file is already applied
to a PoE interface, you must execute the undo apply poe-profile command
to remove the application to the interface before deleting or modifying the PoE
configuration file.
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If you have configured a PoE interface through
the command line, you cannot configure it through a PoE configuration file
again. If you want to reconfigure the interface through a PoE configuration
file, you must first remove the command line configuration on the PoE
interface.
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You must use the same mode (command line or PoE
configuration file) to configure the poe max-power max-power and poe
priority { critical | high | low } commands.
1.4 Configuring PD Power Management
The power priority of a PD depends on the
priority of the PoE interface. The priority levels of PoE interfaces include
critical, high and low in descending order. Power supply to a PD is subject to
PD power management policies.
All PSEs implement the same PD power
management policies. When the PSE supplies power to a PD,
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By default, no power will be supplied to a new
PD if the PSE power is overloaded.
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Under the control of a priority policy, the PD
with a lower priority is first powered off to guarantee the power supply to the
new PD with a higher priority when the PSE power is overloaded.
If the sudden
increase of the power of the PD results in PSE power overload, power supply to
the PD on the PoE interface with a lower priority will be stopped.
If the guaranteed remaining PSE power
(power allocated to the critical PoE interface subtracted from maximum PSE
power, regardless of whether PoE is enabled for the PoE interface) is lower
than the maximum power of the PoE interface, you will fail to set the priority
of the PoE interface to critical. Otherwise, you can succeed in setting
the priority to critical, and this PoE interface will preempt the power
of other PoE interfaces with a lower priority level. In the latter case, the
PoE interfaces whose power is preempted will be powered off, but their
configurations will remain unchanged. When you change the priority of a PoE
interface from critical to a lower level, the PDs connecting to other PoE
interfaces will have an opportunity of being powered.
I. Configuration prerequisites
Enable PoE for PoE interfaces.
II. Configuration procedure
Follow these steps to configure PD power
management:
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Configure the power priority for a PoE
interface
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Configure the power priority for the PoE
interface in PoE interface view
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interface interface-type interface-number
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Use either command.
By default, the power priority of a PoE
interface is low.
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poe priority { critical
| high | low }
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Configure the power priority for the PoE
interface in PoE configuration file view
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poe-profile profile-name [ index ]
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poe priority { critical | high | low }
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Configure a PD power management priority
policy
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poe pd-policy priority
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Optional
By default, no PD power management
priority policy is configured.
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1.5 Configuring a Power Alarm Threshold for
the PSE
When the current power utilization of the
PSE is above or below the alarm threshold for the first time, the system will
send a Trap message.
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Configure a power alarm threshold for the
PSE
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poe utilization-threshold utilization-threshold-value
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Optional
80% by default.
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1.6 Upgrading PSE Processing Software
Online
You can upgrade the PSE processing software
online in either of the following two modes:
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refresh mode
This mode enables you to update the PSE
processing software without deleting it. Normally, you can upgrade the PSE
processing software in the refresh mode through the command line.
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full mode
This mode deletes the PSE processing
software and reloads it. When the PSE processing software is damaged (in this
case, you can execute none of PoE commands successfully), you can upgrade the
PSE software processing software in full mode to restore the PSE function.
Online PSE processing software upgrade may
be unexpectedly interrupted (for example, an error results in device reboot).
If you fail to upgrade the PSE processing software in full mode after reboot,
you can power off the device and restart it before upgrading it again. After
upgrade, restart the device manually to make the original PoE configurations
take effect.
Follow these steps to upgrade the PSE
processing software online:
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Upgrade the PSE processing software
online
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poe update { full | refresh } filename
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Optional
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1.7 Configuring a PD Disconnection Detection Mode
To detect the PD
connection with PSE, PoE provides two detection modes: AC detection and DC
detection. The AC detection mode is energy saving relative to the DC detection
mode.
Follow these steps to configure a PD
disconnection detection mode:
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Configure a PD disconnection detection
mode
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poe disconnect { ac | dc }
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Optional
The default PD disconnection detection
mode is AC.
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Caution:
If you adjust the PD disconnection detection mode when the device is
running, the connected PDs will be powered off. Therefore, be cautious to do
so.
There are standard PDs and nonstandard PDs.
Usually, the PSE can detect only standard PDs and supply power to them. The PSE
can detect nonstandard PDs and supply power to them only after the PSE is
enabled to detect nonstandard PDs.
Follow these steps to enable the PSE to
detect nonstandard PDs:
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To do…
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Use the command…
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Remarks
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Enter system view
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system-view
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—
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Enable the PSE to detect nonstandard PDs
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poe legacy enable
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Optional
Disabled by default.
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To do…
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Use the command…
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Remarks
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Display the mapping between ID, module,
and slot of all PSEs.
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display poe device
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Available in any view
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Display the power state and information
of the specified PoE interface
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display poe interface [ interface-type interface-number ]
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Display the power information of a PoE
interface(s)
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display poe interface power [ interface-type interface-number ]
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Display the information of PSE
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display poe pse
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Display all information of the
configurations and applications of the PoE configuration file
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display poe-profile [ index index | name profile-name
]
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Display all information of the
configurations and applications of the PoE configuration file applied to the
specified PoE interface
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display poe-profile interface interface-type interface-number
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I. Network requirements
The device provides power supply for PDs
through PoE interfaces.
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GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2
are connected to IP telephones.
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GigabitEthernet 1/0/11 and GigabitEthernet
1/0/12 are connected to access point (AP) devices.
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The power priority of GigabitEthernet 1/0/2 is
critical.
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The power of the AP device connected to
GigabitEthernet 1/0/11 does not exceed 9,000 milliwatts.
II. Network diagram
Figure
1-1 Network diagram for PoE
III. Configuration procedure
# Enable PoE on GigabitEthernet 1/0/1,
GigabitEthernet 1/0/2, GigabitEthernet 1/0/11, and GigabitEthernet 1/0/12.
<Sysname> system-view
[Sysname] interface GigabitEthernet
1/0/1
[Sysname-GigabitEthernet1/0/1] poe
enable
[Sysname-GigabitEthernet1/0/1] quit
[Sysname] interface GigabitEthernet
1/0/2
[Sysname-GigabitEthernet1/0/2] poe
enable
[Sysname-GigabitEthernet1/0/2] quit
[Sysname] interface GigabitEthernet
1/0/11
[Sysname-GigabitEthernet1/0/11] poe
enable
[Sysname-GigabitEthernet1/0/11] quit
[Sysname] interface GigabitEthernet
1/0/12
[Sysname-GigabitEthernet1/0/12] poe
enable
[Sysname-GigabitEthernet1/0/12] quit
# Set the power priority level of
GigabitEthernet 1/0/2 to critical.
<Sysname> system-view
[Sysname] interface GigabitEthernet
1/0/2
[Sysname-GigabitEthernet1/0/2] poe
priority critical
[Sysname-GigabitEthernet1/0/2] quit
# Set the maximum power of GigabitEthernet
1/0/11 to 9,000 milliwatts.
[Sysname] interface GigabitEthernet
1/0/11
[Sysname-GigabitEthernet1/0/11] poe
max-power 9000
[Sysname-GigabitEthernet1/0/11] quit
After the configuration takes effect, the
IP phone and AR device are powered and can work normally.
Symptom 1:
Setting of the priority of a PoE interface to critical fails.
Analysis:
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The guaranteed remaining power of the PSE is
lower than the maximum power of the PoE interface.
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The priority of the PoE interface is already
set.
Solution:
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In the first case, you can solve the problem by
reducing the maximum power of the PoE interface when the guaranteed remaining
power of the PSE cannot be modified.
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In the second case, you should first remove the
priority already configured.
Symptom 2:
Applying a PoE configuration file to a PoE interface fails.
Analysis:
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Some configurations in the PoE configuration
file are already configured.
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Some configurations in the PoE configuration
file do not meet the configuration requirements of the PoE interface.
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Another PoE configuration file is already
applied to the PoE interface.
Solution:
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In the first case, you can solve the problem by
removing the original configurations of those configurations.
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In the second case, you need to modify some
configurations in the PoE configuration file.
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In the third case, you need to remove the
application of the undesired PoE configuration file to the PoE interface.
