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, 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.
The support for the
PoE power type depends on the device model.
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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 that comply with the specification,
classifies them, and supplies power to them. When detecting a PD is unplugged,
the PSE stops supplying the 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 unit 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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Adopt the command line.
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Configure a PoE configuration file and apply 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 batch
configure PoE interfaces.
Caution:
You can adopt
either mode to configure, modify, or delete a PoE configuration parameter under
the same PoE interface.
The PSE applies power to a PoE interface in
two modes. For a device with only signal cables, power is supplied over signal
cables. An S5500-SI switch cannot provide power supply through spare cables. So
you need to use an intermediate device for an S5500-SI switch to provide power
supply to devices that can only be powered by spare cables.
To clearly identify the PD connected to a PoE
interface, you can give a PD description.
Follow these steps to configure 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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—
|
|
Enter PoE interface view
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interface interface-type interface-number
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—
|
|
Enable PoE
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poe enable
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Required
By default, PoE is disabled on the PoE
interface.
|
|
Configure the maximum power for the PoE
interface
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poe max-power max-power
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Optional
By default, the maximum power on the PoE
interface is 15,400 milliwatts.
|
|
Configure the PoE mode for the PoE
interface
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poe mode signal
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Optional
By default, the PoE mode is signal
(power over signal cables).
|
|
Configure a description for the PD
connected to the PoE interface
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poe pd-description string
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Optional
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A PoE configuration file is used to batch
configure PoE interfaces with the same attributes to simplify operations. This
configuration method is a supplement to the common 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
|
|
Enter system view
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system-view
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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
|
|
Enable PoE for the PoE interface
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poe enable
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Required
By default, PoE is disabled on a PoE
interface.
|
|
Configure the maximum power for the PoE
interface
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poe max-power max-power
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Optional
By default, the maximum power on the PoE
interface is 15,400 milliwatts.
|
|
Configure the PoE mode for the PoE
interface
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poe mode signal
|
Optional
By default, the PoE mode is signal
(power over signal cables).
|
|
Return to system view
|
quit
|
—
|
|
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
|
|
Apply the PoE configuration file to the
current PoE interface in PoE interface view
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interface interface-type interface-number
|
|
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 guaranteed remaining PSE power
(maximum PSE power – power allocated to the critical PoE interface,
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, 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 seizing power.
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
|
|
Enter system view
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system-view
|
—
|
|
Configure the power priority for a PoE
interface.
|
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 approach.
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 ]
|
|
poe priority { critical | high | low }
|
|
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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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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When the PSE starts or stops supplying power to
a PD, the system will send a Trap message, too.
Follow these steps to configure a power
alarm threshold for the PSE:
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To do…
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Use the command…
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Remarks
|
|
Enter system view
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system-view
|
—
|
|
Configure a power alarm threshold for the
PSE
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poe utilization-threshold utilization-threshold-value
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Optional
By default, the power alarm threshold for
the PSE is 80%.
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1.6 Upgrading PSE Processing Software Online
You can upgrade the PSE processing software
online in either of the following modes:
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Refresh mode
Normally, you can upgrade the PSE
processing software in the Refresh mode through the command line.
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Full mode
When an exception, such as interruption (power
failure) or error, occurs during the upgrade in Refresh mode, you can upgrade
the PSE processing software in Full mode.
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. The support for this upgrade
method depends on the device model.
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
|
|
Enter system view
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system-view
|
—
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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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|
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 depends on the device model.
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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!
1.8 Enabling the PSE to Detect Nonstandard PDs
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
|
|
Enter system view
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system-view
|
—
|
|
Enable the PSE to supply power to the
detected nonstandard PDs
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poe legacy enable
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Optional
By default, the PSE is disabled from supplying
power to the detected nonstandard PDs.
|
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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.
|
display poe device
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Available in any view
|
|
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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Available in any view
|
|
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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Available in any view
|
|
Display the information of PSE
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display poe pse [ pse-id ]
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Available in any view
|
|
Display the power state and information
of PoE interfaces connected with the PSE
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display poe interface [ interface-type interfece-number ]
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Available in any view
|
|
Display the power of all PoE interfaces
connected with the PSE
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display poe interface power [ interface-type interface-number ]
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Available in any view
|
|
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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Available in any view
|
|
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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Available in any view
|
I. Network requirements
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GigabitEthernet1/0/1 and GigabitEthernet1/0/2
are connected to IP telephones.
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GigabitEthernet1/0/5 and GigabitEthernet1/0/6
are connected to access point (AP) devices.
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The power priority of GigabitEthernet1/0/2
is critical.
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The power of the AP device connected to GigabitEthernet1/0/5 does not exceed 9,000 milliwatts.
II. Network diagram
Figure 1-1 Network diagram for PoE
III. Configuration procedure
# Enable PoE on GigabitEthernet1/0/1,
GigabitEthernet1/0/2, GigabitEthernet1/0/5, and GigabitEthernet1/0/6.
<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 1/0/5
[Sysname-GigabitEthernet1/0/5] poe
enable
[Sysname-GigabitEthernet1/0/5]quit
[Sysname] interface gigabitethernet 1/0/6
[Sysname-GigabitEthernet1/0/6] poe
enable
# Set the power priority level of
GigabitEthernet1/0/2 to critical.
<Sysname> sytem view
[Sysname] interface gigabitethernet 1/0/2
[Sysname-GigabitEthernet1/0/2] poe
priority critical
# Set the maximum power of GigabitEthernet1/0/5
to 9,000 milliwatts.
[Sysname] interface gigabitethernet 1/0/5
[Sysname-GigabitEthernet1/0/5] poe
max-power 9000
Symptom:
Setting 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 former case, you can solve the problem by
increasing the maximum PSE power, or 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 latter case, you should first remove the
priority already configured.
Symptom:
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 case 1, you can solve the problem by removing
the original configurations of those configurations.
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In case 2, you need to need to modify some
configurations in the PoE configuration file.
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In case 3, you need to remove the application of
the undesired PoE configuration file to the PoE interface.
Symptom:
Provided that parameters are valid, configuring an AC input under-voltage
threshold fails.
Analysis:
The AC input under-voltage threshold is
greater than or equal to the AC input over-voltage threshold.
Solution:
You can drop the AC input under-voltage
threshold below the AC input over-voltage threshold.
