Chapter 11

Power over Ethernet (PoE)

Introduction ................................................................................................. 11-2

Power Capacity ............................................................................................ 11-3
Port Prioritisation ......................................................................................... 11-4
PoE Device Classes ....................................................................................... 11-5
PoE Threshold .............................................................................................. 11-5
Upgrading PoE Firmware .............................................................................. 11-6
Command Reference ................................................................................... 11-7
disable poe debug ................................................................................. 11-7
disable poe port .................................................................................... 11-8
enable poe debug ................................................................................. 11-8
enable poe port ..................................................................................... 11-9
set poe detect ....................................................................................... 11-9
set poe firmware ................................................................................. 11-10
set poe port ........................................................................................ 11-11
set poe threshold ................................................................................ 11-12
show poe ............................................................................................ 11-13
show poe version ................................................................................ 11-16
11-2 AlliedWare OS Software Reference

Introduction
Power Over Ethernet (PoE) is a mechanism for supplying power to network
devices over the same cabling used to carry network traffic. PoE allows devices
that require power, called Powered Devices (PDs), such as IP telephones,
wireless LAN Access Points and network cameras, to receive power in
addition to data over your existing infrastructure without needing to upgrade
it. This feature can simplify network installation and maintenance by allowing
you to use the switch as a central power source for other network devices.

A device that can source power such as an Ethernet switch is termed as Power
Sourcing Equipment (PSE). Power Sourcing Equipment can provide power
along with data over existing LAN cabling as long as the Powered Device is
connected and needs power.

PSE and PD functionality is specified in the IEEE 802.3af standard, which is an

amendment to the existing IEEE 802.3 standards.

Figure 11-1: Examples of powered devices you can use with your PoE switch

Wireless LAN
Access Point
Hub

Network Camera
VoIP Phone
poe1

Benefits of PoE There are several benefits that the PoE feature of the switch adds to the
installation and maintenance of your network.
■ The IEEE 802.3af standard describes two methods for implementing PoE
over twisted pair cabling. One method uses the same cables that carry the
network traffic and the other the spare strands. The PoE implementation
on the AT-8624PoE switch transmits power over the same strands that
carry the network traffic (strands 1, 2, 3 and 6). This power transfer does
not interfere with the network traffic, and means that power and the
network traffic can coexist on the same strands simultaneously.
■ PoE can simplify the installation of your network. The selection of a
location for a network device is often limited by whether there is a power
source nearby. This often limits equipment placement or requires the
added time and cost of having additional electrical sources installed. With
PoE, you can install PoE-compatible devices wherever they are needed
without having to worry about whether there are power sources nearby.

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■ PoE requires little configuration or management. The switch automatically

determines whether a device connected to a port is a powered device or
not. A port on the switch connected to a powered device can supply up to
15.4 watts of power to the device, while at the same time providing
standard 10/100 Mbps Ethernet functionality. A port connected to a
network node that is not a powered device (that is, a device that receives
its power from another power source) functions as a regular Ethernet port,
without PoE. The PoE feature remains activated on the port but no power
is delivered to the device.

Power Capacity
The AT-8624PoE switch can provide a maximum of 15.4 W per port on Ports 1
to 24.

PoE is not supported on expansion modules.

In the default configuration, the switch can provide the maximum of 15.4 W to
all 24 ports for a total power capability of 370 W, which is below the maximum
available.

The fact that the maximum power requirement falls below the maximum
amount of power available means that you can connect powered devices to all
the ports on the switch (excluding optional expansion ports) without having to
be concerned about exceeding the available power, even if the all the powered
devices require the maximum of 15.4 W.

You can disable PoE on a per-port basis using the disable poe port command.
You can also reduce the maximum amount of power a port can source, from
the maximum of 15.4 W, using the command:
set poe [{port=port-list|ALL}] [priority=low|high|critical]
[powerlimit=value]

However, configuring the power limit on the switch will probably not be
necessary. As already mentioned, the power supply in the switch can provide
enough power to meet the needs of all 24 base ports, even if all are connected to
power devices requiring the maximum of 15.4 W. Additionally, since a switch
port can automatically determine whether or not the device connected to it is
PoE-compliant, and if it is, how much power is required, there should be little
need for you to configure PoE at all.

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Port Prioritisation
Port prioritisation is the way in which the switch determines which ports are to
receive PoE in the event that the needs of the powered devices exceeds the
available power resources of the switch. The AT-8624PoE switch prioritises
power to the ports without the need for user intervention.

This discussion does not apply to the AT-8624PoE switch since its power supply can
deliver the maximum of 15.4 W to all 24 based ports simultaneously.

This discussion becomes relevant only if, at some later date, Allied Telesis releases an
AT-8600 Series switch with PoE capability that has a power supply that cannot service
all ports simultaneously.

If the powered devices connected to a switch require more power than the
switch is capable of delivering, the switch will deny power to some ports based
on a system called port prioritisation. You can use port prioritisation to ensure
that powered devices critical to the operations of your network are given
preferential treatment by the switch in the distribution of power, should the
demands of the devices exceed the available capacity.

There are three priority levels:

■ Critical
■ High
■ Low

You can set the port priority using the command:

set poe [{port=port-list|ALL}] [priority=low|high|critical]
[powerlimit=value]

You can see the priority set on a particular port by entering a port number in
the command:
show poe port=n

Critical is the highest priority level. Ports set to this level are guaranteed power
before any ports assigned to the other two priority levels. Ports assigned to the
other priority levels receive power only if all the Critical ports are receiving
power. Your most critical powered devices should be assigned to this level. If
there is not enough power to support all the ports set to the Critical priority
level, power is provided to the ports based on port number, in ascending order.

High is the second highest level. Ports set to this level receive power only if all
the ports set to the Critical level are already receiving power. If there is not
enough power to support all of the ports set to the High priority level, power is
provided to the ports based on port number, in ascending order.

Low is the lowest priority level. This is the default setting. Ports set to this level
only receive power if all the ports assigned to the other two levels are already
receiving power. As with the other levels, if there is not enough power to
support all of the ports set to the Low priority level, power is provided to the
ports based on port number, in ascending order.

Power allocation is dynamic. Ports supplying power to powered devices may

cease power transmission if the switch’s power capacity has reached maximum
usage and new powered devices, connected to ports with a higher priority,
become active.
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PoE Device Classes

The IEEE 802.3af standard specifies classes for powered devices based on
power usage. These are:

Table 11-1: PoE device classes

Class Power usage

0 0.44 W to 12.95 W
1 0.44 W to 3.84 W
2 3.84 W to 6.49 W
3 6.49 W to 12.95 W
4 Reserved for future use.

You can view the class of a powered device by using the show poe command
set on a particular port by entering a port number in the command:
show poe port=n

Although the IEEE standard defines the maximum amount of power supplied
by a port to be 15.4 W, in practice, due to power loss in the cable itself, the
maximum power available to a powered device is limited to approximately
12.95 W. Some power is likely to be lost in the twisted pair cable as the current
travels from the switch to the device. For those devices needing 12.95 W, the
extra watts act as compensation for this possible loss.

PoE Threshold
The switch sends an SNMP trap to your management workstation and enters
an event in the event log whenever the total power requirements of the
powered devices exceeds the specified percentage of the total maximum power
available on the switch. At the default setting of 95%, the switch sends an
SNMP trap when the PoE devices require more than 95% of the maximum
available power on the switch.

You can adjust the threshold using the command:

set poe threshold=value

For your management workstations to receive traps from the switch, you must
configure SNMP on the switch by specifying the IP address of the
workstations.

The switch will also enter an event in the event log whenever power
consumption of the switch has gone below the power limit threshold.

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Upgrading PoE Firmware

You can upgrade the version of PoE firmware that your system uses by
entering the set poe firmware command. This command downloads PoE
firmware to the PoE Controller.

Your switch must already have a valid firmware file with the extension .s19
present in its flash. If it does not, you can download one to the flash using the
load command on page 5-31 of Chapter 5, Managing Configuration Files and
Software Versions.

The switch prompts you for confirmation before it begins upgrading the
firmware. The upgrade may take a while to complete, depending on the size of
your firmware file.

You must not restart the switch while the firmware upgrade is in progress. If you
restart the switch, the firmware upgrade will terminate abruptly, which will corrupt the
firmware and cause PoE operations to fail in the subsequent startup.

During the upgrade the following limitations apply:

■ PoE commands do not execute.
■ You cannot use any PoE ports for powered devices, as Power over Ethernet
is temporarily disabled. However, any non-powered devices that are
connected to PoE ports will continue to operate normally.
■ You should avoid deleting, re-naming, or copying any files.

All PoE configurations are restored once the upgrade has successfully
completed. You do not need to reconfigure POE or restart the switch for the
new firmware to take effect.

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Command Reference
This section describes the commands available for configuring and monitoring
PoE on the switch.

See “Conventions” on page xxxviii of About this Software Reference for

additional conventions used to describe command syntax. See Appendix A,
Messages for a complete list of messages and meanings.

disable poe debug

Syntax DISable POE DEBug[={ALL|DEBug|TRAce|ERRor|FATal|TESt}]

Description This command disables the specified PoE debugging modes.

Parameter Value Description

DEBug Use the debug parameter to specify the debugging modes to disable.
ALL Disables all PoE debugging
DEBug
TRAce Disables high-level, essential debugging, for example,
information about message types
ERRor Disables debugging of any error conditions that may occur
FATal during PoE operation.
TESt Disables test debugging mode
Default: all

Examples To disable all PoE debugging, use one of the commands:

dis poe deb=all
dis poe debug=deb

To disable high-level, essential debugging, use the command:

dis poe deb=tra

See Also enable poe debug

show poe

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disable poe port

Syntax DISable POE [POrt={port-list|ALL}]

where port-list is a port number, a range of port numbers (specified as n-m), or

a comma-separated list of port numbers and/or ranges. Port numbers start at 1
and end at 24.

Description This command disables PoE on a port. The port continues to provide standard
Ethernet connectivity even when PoE is disabled. PoE is enabled by default.

The port parameter specifies a port number, a range of port numbers (specified
as n-m), or a comma-separated list of port numbers and/or ranges. Specify all
to disable PoE on all ports.

Example To disable PoE on ports 5 and 7, use the command:

dis poe po=5,7

Related Commands enable poe port

enable poe debug

Syntax ENAble POE DEBug[={ALL|DEBug|TRAce|ERRor|FATal|TESt}]

Description This command enables the specified PoE debugging modes.

Parameter Value Description

DEBug Use the debug parameter to specify the debugging modes to enable.
ALL Enables all PoE debugging
DEBug
TRAce Enables high-level, essential debugging, for example,
information about message types
ERRor Enables debugging of any error conditions that may occur
FATal during PoE operation.
TESt Enables test debugging mode
Default: No debugging is enabled

Example To enable error debugging, use one of the commands:

ena poe deb=err
ena poe deb=fat

See Also disable poe debug

show poe

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enable poe port

Syntax ENAble POE [POrt={port-list|ALL}]

This command enables PoE on a port. PoE is enabled by default.

The port parameter specifies a port number, a range of port numbers (specified
as n-m), or a comma-separated list of port numbers and/or ranges. Port
numbers start at 1 and end at 24. The all parameter enables PoE on all ports.

Example To enable PoE on port 2, use the command:

ena poe po=2

Related Commands disable poe port

set poe detect

Syntax SET POE DETect={IEEE|LEGacy}

Parameter Value Description

DETect The power detection mode.
IEEE IEEE standard detection is enabled according to the IEEE
802.3af standard, in which a valid resistance and capacitance
is used for detecting a valid powered device.
LEGacy Legacy mode. IEEE mode is implemented first and, if it fails,
Legacy detection is used, where a large capacitance value is
used to detect a legacy powered device.
Default: ieee

Example To set the detection mode to IEEE, use the command:

set poe det=ieee

Related Commands set poe port

set poe threshold
show poe

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set poe firmware

Syntax SET POE FIRMware=filename

where filename is the name of a valid firmware file that is already present in the
flash. A valid firmware file must be either Version 2.9.0 or 5.0.1, and have the
extension .s19.

Description This command upgrades the PoE firmware in the PoE Controller, if the switch
finds valid PoE firmware in its flash. Firmware is downloaded to the flash
using the load command on page 5-31 of Chapter 5, Managing Configuration
Files and Software Versions.

The switch prompts you for confirmation before it begins upgrading the
firmware. The upgrade may take a while to complete, depending on the size of
your firmware file.

You must not restart the switch while the firmware upgrade is in progress. If you
restart the switch, the firmware upgrade will terminate abruptly, which will corrupt the
firmware and cause PoE operations to fail in the subsequent startup.

During the upgrade the following limitations apply:

■ Other PoE commands do not execute.
■ You cannot use any PoE ports for powered devices, as Power over Ethernet
is temporarily disabled. However, any non-powered devices that are
connected to PoE ports will continue to operate normally.
■ You should avoid deleting, re-naming, or copying any files.

All PoE configurations are restored once the upgrade has successfully
completed. You do not need to reconfigure POE or restart the switch for the
new firmware to take effect.

The new firmware version is permanently stored in the PoE hardware. This
remains in the PoE hardware even if you delete the .sig file from flash memory.

Example To download the PoE firmware file v2.9.0 to the PoE Controller, use the
command:
set poe firm=pol30k.s19

Related commands show poe version

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set poe port

Syntax SET POE [{POrt=port-list|ALL}] [POWerlimit=value]

[PRIOrity=LOW|HIGH|CRITICAL]

Description This command sets the PoE settings on a port.

Parameter Description
POrt Sets PoE on a specific port number, a range of port numbers (specified as n-
m), or a comma-separated list of port numbers and/or ranges. Port numbers
start at 1 and end at 24. Specifying all sets PoE on all ports.
POWerlimit The maximum amount of power a powered device can draw from the port.
Default: 15400mW (15.4W)
PRIOrity Determines which ports receive PoE when powered device consumption
exceeds the available power resources of the switch. One of Low, High, or
Critical.
Default: Low

When an individual port powerlimit is set, an additional margin of approximately

400mW is provided to allow for line loss.

Examples To set the priority on ports 6 and 11 to high, use the command:
set poe po=6,11 prio=high

To set the maximum power on port 14 to 12,500 mW, use the command:
set poe po=14 pow=12500

Related Commands set poe threshold

set poe detect
show poe

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set poe threshold

Syntax SET POE THReshold=value

where value is specified as a percentage of the total amount of PoE available.

The range is 1 to 100.

Description The switch enters an event in the event log whenever the total power
requirements of the powered devices cross the specified percentage threshold
of the total maximum power available on the switch. The crossing of this
threshold may be in either an upward or downward direction. This command
sets this adjustable threshold.

Example To set the threshold to 80% of the available power, use the command:
set poe thr=80

Related Commands set poe port

set poe detect
show poe

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show poe

Syntax SHow POE [PORt={port-list|ALL}]

where port-list specifies a port number, a range of port numbers (specified as n-

m), or a comma-separated list of port numbers and/or ranges. Port numbers
start at 1 and end at 24.

Description This command displays information about Power over Ethernet for the
specified port or ports.

If no port number is specified, summary information about all PoE ports is

displayed, as shown in Table 11-2 on page 11-14. If an port, or range of ports is
specified, more detailed information is displayed. If all is specified, detailed
information about all Power over Ethernet ports is displayed.

Entering this command without specifying a port displays the information

shown in Table 11-2 on page 11-14.

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Figure 11-2: Example output from the show poe command

PoE Global Power Status:

Max Available Power.... 400 W

Power Threshold........ 95 percent
Consumed Power......... 0 W
Available Power........ 400 W
Power Usage............ 0.00 percent
Power Detect Mode...... IEEE
Min Shutdown Voltage... 44.0 V
Max Shutdown Voltage... 57.0 V

PoE All Ports Power Status Summary:

Port PoE Status Consumed Power(mW) Power State

----------------------------------------------------------------------
1 ENABLED 13100 ON - Valid PD detected
2 ENABLED 0 OFF - Detection in process
3 ENABLED 13100 ON - Valid PD detected
4 ENABLED 0 OFF - Detection in process
5 ENABLED 13100 ON - Valid PD detected
6 ENABLED 0 OFF - Detection in process
7 ENABLED 13100 ON - Valid PD detected
8 ENABLED 0 OFF - Detection in process
9 ENABLED 0 OFF - Overload state
10 ENABLED 0 OFF - Detection in process
11 ENABLED 0 OFF - Overload state
12 ENABLED 0 OFF - Detection in process
13 ENABLED 0 OFF - Overload state
14 ENABLED 0 OFF - Detection in process
15 ENABLED 12900 ON - Valid PD detected
16 ENABLED 0 OFF - Detection in process
17 ENABLED 12900 ON - Valid PD detected
18 ENABLED 0 OFF - Detection in process
19 ENABLED 12900 ON - Valid PD detected
20 ENABLED 0 OFF - Detection in process
21 ENABLED 12900 ON - Valid PD detected
22 ENABLED 0 OFF - Detection in process
23 ENABLED 12900 ON - Valid PD detected
24 ENABLED 0 OFF - Detection in process

Table 11-2: Parameters displayed in the output of the show poe command

Parameter Meaning
Max Available Power Total available power for PoE supplied by the switch.
Power Threshold A percentage of the maximum available power.
Default: 95%
Consumed Power The amount of power being used by the powered devices.
Available Power The amount of power available for additional powered
devices.
Power Usage The amount of power currently consumed by the powered
devices connected to the switch. The value is give as a
percentage of the total amount of power available.
Power Detect Mode Displays the power detection mode in the switch, one of
IEEE or Legacy.

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Table 11-2: Parameters displayed in the output of the show poe command (Continued)

Parameter Meaning
Min Shutdown Voltage The minimum threshold voltage at which the switch shuts
down PoE. This value is not adjustable.
Max Shutdown Voltage The maximum threshold voltage at which the switch shuts
down PoE This value is not adjustable.

Figure 11-3: Example output from the show poe port=1 command

PoE Status Of Port 1:

PoE Status......... ENABLED
Power Limit....... 15,400 mW
Power Priority..... LOW
Power State........ OFF - Detection in process
Power Consumed..... 0 mW
Power Class........ 0
Voltage............ 0.0 V
Current............ 0 mA

Table 11-3: Parameters displayed in the output of the show poe port=1 command

Parameter Meaning
PoE Status Whether PoE is enabled or disabled on the port.
Default: Enabled
Power Limit The maximum amount of power allowed by the port for the
device.
Default: 15,400 milliWatts (15.4 W)
Power Priority The port priority.
Power State Whether power is being supplied to the device. ON means
that the port is providing power to a powered device. OFF
means the device is not a powered device or PoE has been
disabled on the port.
Power Consumed The amount of power in milliWatts currently consumed by
the powered device connected to the port.
If the port is not connected to a powered device, this value
will be 0 (zero).
Power Class The IEEE 802.3af class of the device.
Voltage The voltage being provided to the powered device.
Current The current drawn by the powered device.

Examples To display general PoE information, use the command:

sh poe

To display PoE information about port 1, use the command:

sh poe po=1

Related Commands set poe port

set poe threshold
set poe detect
show poe version

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show poe version

Syntax SHow POE VERsion

Description Use this command to display the version number of the PoE firmware that is
currently running on your switch.

Figure 11-4: Example output from the show poe version command

PoE version information:

Firmware version .... 2.9.0

Example To display the PoE firmware version number, use the command:
sh poe ver

See Also set poe firmware

show poe

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