ENT-AN1183-4.00 Application Note PoE Configuration Guide

ENT-AN1183-4.00 Application NotePoE Configuration Guide

VPPD-04307. 1.0 8/19

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VPPD-04307 ENT-AN1183-4.00 Application Note Revision 1.0 iii

Contents

1 Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Revision 1.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2 Understanding PoE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.1 Power Sourcing Equipment (PSE) and Powered Device (PD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.2 Power Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.2.1 Actual Consumption Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.2.2 Reserved Power Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.3 Configuration Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.3.1 Actual Consumption with Reserved Power Determined by Allocation . . . . . . . . . . . . . . . . . . . . 32.3.2 Capacitor Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.3.3 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.3.4 Port PoE/PoE+ Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.3.5 Port Priority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.3.6 Port Maximum Power in Allocation Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.4 PD Statuses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.4.1 Power, Current Consumption, and Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.4.2 Power Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.4.3 LLDP Neighbor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

VPPD-04307 ENT-AN1183-4.00 Application Note Revision 1.0 iv

Figures

Figure 1 PoE Configuration: Power Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Figure 2 PoE Configuration: Capacitor Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Figure 3 PoE Configuration: Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Figure 4 Display Current PoE Operation Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Figure 5 Display LLDP Neighbor PoE Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

VPPD-04307 ENT-AN1183-4.00 Application Note Revision 1.0 1

Tables

Table 1 PD Classes: Maximum Power Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Revision History


1 Revision History

The revision history describes the changes that were implemented in the document. The changes are listed by revision, starting with the most current publication.

1.1 Revision 1.0Revision 1.0 was the first publication of this document.

Understanding PoE


2 Understanding PoE

Power over Ethernet (PoE) transfers power to a device connected to the switch over the Ethernet cabling—this removes the need to mount both power and Ethernet cables. This document describes basic PoE terms for Microsemi software use.

2.1 Power Sourcing Equipment (PSE) and Powered Device (PD)The power sourcing equipment (PSE) is a device (in this case a Microsemi switch) that delivers power to the powered device (PD). PDs come in class 1 through 4. The PD class determines the maximum power that the PD consumes, which is detected by measuring some of the PD resistor and capacitor values. All these tasks are performed by hardware only.

PDs in class 1, 2, and 3 are defined in IEEE 802.3af (PoE). PDs in class 4 are part of IEEE 802.3at (PoE+).

The following table lists maximum power consumption for each class.

2.2 Power ManagementPower management means determining how much power the PDs consume and request (a request for a specific amount of power called a “reserve”). A PD must turn off automatically when its power consumption/request exceeds the total power that the power supply can deliver. Only some PDs must turn off if the power supply can not power all connected PDs. The PDs that are turned off are determined by both the priority of the port to which the PD is connected and the power management configuration.

IEEE has not defined PD power management; therefore, designers must decide. Microsemi supports multiple PoE vendors. Some vendors have their own controller, while others require Microsemi software to control power management.

The software auto-detects the PoE chip and sets up the corresponding power management.When configuration must be done, one of the following power management modes should be selected based on power consumption or reservation.

Note: For both of the following modes, the ports are shut down according to priority. If two ports have the same priority, the port with the highest port number is shut down

2.2.1 Actual Consumption ModeIn this power management mode, ports are shut down when the actual power consumption for all ports exceeds the amount of power that the power supply can deliver, or if the actual power consumption for a given PD exceeds the reserved power for that port. A turned-off PD is turned on after a random time interval in order to see if the PD still consumes too much power. If it still consumes too much power, it is turned off again. This is a repeating process, as a PD continuously turns on and off.

Table 1 • PD Classes: Maximum Power Consumption

Class Maximum Power Consumption1 4 W

2 7 W

3 15.4 W

4 30 W

Understanding PoE


2.2.2 Reserved Power Mode In this power management mode, ports are shut down when the total reserved powered exceeds the amount of power that the power supply can deliver. The port power is not turned on if the PD requests more power than available from the power supply.

Reservation of PD power can occur through three different modes:

• Allocated mode: the user allocates the amount of power reserved for each port. The reserved power for each port (where PD resides) is specified in the maximum power fields for each port. If a PD uses more power than specified, it will be turned off. Only consumption management is supported in allocation mode.

• Class mode: each port automatically determines how much power to reserve according to the class of the connected PD, and reserves the power accordingly. See Table 1, page 2.

• LLDP-MED mode: similar to Class mode, but each port determines the amount of power it reserves by exchanging PoE information using the Link Layer Discovery Protocol (LLDP), and reserves power accordingly. If no LLDP information is available for a port, the port will reserve power using the class mode.

Note: Maximum Power fields take effect only in allocated mode.

2.3 Configuration ExamplesThe following PoE configuration examples use both the web interface and the Industrial Command Line Interface (ICLI).

It is recommended to restore defaults before starting to configure any of the examples in the following sections.

# reload defaults

2.3.1 Actual Consumption with Reserved Power Determined by Allocation The following steps set the actual consumption with reserved power determined by allocation.

1. Click Configuration > PoE. Then, under Power Over Ethernet Configuration, select Reserved Power determined by Allocation and Power Management Mode Actual Consumption, as shown in the following illustration.

2. Click Save.

Understanding PoE


Figure 1 • PoE Configuration: Power Management

For ICLI, the Power Management Mode and Reserved Power determined by are combined in one single command. The equivalent ICLI commands are:

# configure terminal(config)# poe management mode ? allocation-consumption Max. port power determined by allocated, and power is managed according to power consumption. class-consumption Max. port power determined by class, and power is managed according to power consumption. class-reserved-power Max. port power determined by class, and power is managed according to reserved power. lldp-consumption Max. port power determined by LLDP Media protocol, and power is managed according to power consumption. E.g. a PD's is class 3 device, but once powered up the PD uses the LLDP protocol to signal that it only requires 11W (and not 15.4W) lldp-reserved-power Max. port power determined by LLDP Media protocol, and power is managed according to reserved power.(config)# poe management mode allocation-consumption(config)# end#

2.3.2 Capacitor DetectionBefore IEEE defined the PoE standards, another PoE detection method known as Capacitor, or Legacy, detection was used. The following example manages this mode:

Understanding PoE


1. Click Configuration > PoE, and then select the Enabled option for Capacitor Detection, as shown in the following illustration.

2. Click Save.Figure 2 • PoE Configuration: Capacitor Detection

The equivalent ICLI commands are:

# configure terminal! Enable PoE legacy detection.(config)# poe capacitor-detect

! Disable PoE legacy detection.(config)# no poe capacitor-detect

(config)# end#

Understanding PoE


2.3.3 Power SupplyIn order to manage the PDs, the software needs to know the amount of power the power supply can deliver. Power supply capacity cannot be auto-detected—it must be keyed in as a configuration parameter.The following example sets the power supply to 140 W.

Note: Typically, the configured power supply value is less than the actual power that the power supply can deliver. This prevents the power supply from being exceeded when the PDs are turned on for a short time for power consumption measurement.

1. Click Configuration > PoE, and then under PoE Power Supply Configuration set up Primary Power Supply (W), as shown in the following illustration.

2. Click Save. Figure 3 • PoE Configuration: Power Supply


configure terminal(config)# poe supply ? 1-180 Maximum power the power supply can deliver.(config)# poe supply 140(config)# end#

Understanding PoE


2.3.4 Port PoE/PoE+ ModePoE mode can disable PoE for a specific port or specify which PoE standard to use. Again, IEEE 802.3af (PoE) defines PD classes 1,2, and 3, while class 4 is defined in IEEE 802.3at (PoE+). If PoE+ mode is selected, then all classes are supported. If PoE mode is selected, then class 4 PDs are limited to 15.4 W.

The following procedure sets PoE mode for Port 2.

1. Click Configuration > PoE, and then under PoE Port Configuration select PoE+ from the PoE Mode list for Port 2 as shown in Figure 1, page 4.

2. Click Save.The equivalent ICLI commands are:

# configure terminal(config)# interface GigabitEthernet 1/2! PoE is enabled by setting the PoE mode to either PoE or PoE+.(config-if)# poe mode ? plus Set mode to PoE+ (Maximum power 30.0 W) standard Set mode to PoE (Maximum power 15.4 W, if port power limit is current above 15.4W, it is automatically adjusted to 15.4W)(config-if)# poe mode plus

! (Optional) Disable PoE on this port.(config-if)# no poe mode

(config-if)# end#

2.3.5 Port PriorityEach port is assigned one of three priorities—low, high, or critical. The lowest priority port turns off when a remote device requires more power than the power supply can deliver. If port priorities are equal, the highest numbered port turns off.

The following example sets a different priority for Port 1 and Port 2.

1. Click Configuration > PoE, and then under PoE Port Configuration select Low for Port 1 and select High for Port, 2 as shown in Figure 1, page 4.


# configure terminal(config-if)# interface GigabitEthernet 1/1(config-if)# poe priority low(config-if)# interface GigabitEthernet 1/2(config-if)# poe priority high(config-if)# end#

2.3.6 Port Maximum Power in Allocation ModeConfigure the maximum power each port can deliver when power management is done by allocation. For example, the following steps set up the maximum allocated power for Port 2:

1. Click Configuration > PoE, and then under PoE Port Configuration section enter 10.2 in the Maximum Power (W) field for Port 2 as shown in Figure 1, page 4.


# configure terminal(config)# interface GigabitEthernet 1/2(config-if)# poe power limit ? <fword2.1> Maximum power for the interface (0-15.4 Watt for PoE standard

Understanding PoE


mode, 0-30.0 Watt for PoE plus mode)(config-if)# poe power limit 10.2(config-if)# end#

2.4 PD StatusesThe following sections discuss various PoE PD statuses and their tracking procedures.

2.4.1 Power, Current Consumption, and ClassPower, current consumption, class, and more can be tracked for currently connected PDs. This is useful for debugging PoE systems. The following illustration displays the currently connected PD’s operation status.

To display this information, click Monitor > PoE.

Figure 4 • Display Current PoE Operation Status


# show poeInterface PD Class Power Port Power Current Reserved Status Used [W] Used [mA]------------------- -------- -------- ---------------- -------- --------GigabitEthernet 1/1 - 0.0 No PD detected 0.0 0GigabitEthernet 1/2 - 0.0 No PD detected 0.0 0GigabitEthernet 1/3 - 0.0 No PD detected 0.0 0GigabitEthernet 1/4 - 0.0 No PD detected 0.0 0GigabitEthernet 1/5 - 0.0 No PD detected 0.0 0GigabitEthernet 1/6 - 0.0 No PD detected 0.0 0GigabitEthernet 1/7 - 0.0 No PD detected 0.0 0GigabitEthernet 1/8 4 30.0 PoE turned ON 1.1 23GigabitEthernet 1/9 - 0.0 No PD detected 0.0 0GigabitEthernet 1/10 - 0.0 No PD detected 0.0 0GigabitEthernet 1/11 - 0.0 No PD detected 0.0 0GigabitEthernet 1/12 - 0.0 No PD detected 0.0 0GigabitEthernet 1/13 - 0.0 No PD detected 0.0 0GigabitEthernet 1/14 - 0.0 No PD detected 0.0 0GigabitEthernet 1/15 - 0.0 No PD detected 0.0 0GigabitEthernet 1/16 3 6.3 PoE turned ON 3.9 82GigabitEthernet 1/17 - 0.0 No PD detected 0.0 0

Understanding PoE


GigabitEthernet 1/18 - 0.0 No PD detected 0.0 0GigabitEthernet 1/19 - 0.0 No PD detected 0.0 0GigabitEthernet 1/20 - 0.0 No PD detected 0.0 0GigabitEthernet 1/21 - 0.0 No PD detected 0.0 0GigabitEthernet 1/22 - 0.0 No PD detected 0.0 0GigabitEthernet 1/23 - 0.0 No PD detected 0.0 0GigabitEthernet 1/24 - 0.0 No PD detected 0.0 0GigabitEthernet 1/25 does not have PoE support2.5GigabitEthernet 1/1 does not have PoE supportTotal - 36.3 - 5.0 #

2.4.2 Power DownAs described in Power Management, page 2, PDs can be powered down by the software. The Port Status column of the status overview indicates why a PD may have been powered down.

“OFF-PD overload” indicates the PD used too much power.

# show poe interface GigabitEthernet 1/1,8,16Interface PD Class Power Port Power Current Reserved Status Used [W] Used [mA]------------------- -------- -------- ---------------- -------- ----------GigabitEthernet 1/1 - 0.0 No PD detected 0.0 0GigabitEthernet 1/8 4 2.0 PoE turned ON 1.1 23igabitEthernet 1/16 3 2.0 PoE turned 3.0 64 OFF-PD overloadTotal - 4.0 - 4.1 87#“OFF-Power budget” indicates total power deliverable by a power supply was exceeded.

Interface PD Class Power Port Power Current Reserved Status Used [W] Used [mA]------------------- -------- -------- ---------------- -------- ----------GigabitEthernet 1/1 - 0.0 No PD detected 0.0 0GigabitEthernet 1/8 4 30.0 PoE turned ON 1.1 23igabitEthernet 1/16 - 6.3 PoE turned 0.0 0 OFF-Power budget exceededTotal - 36.3 - 1.1 23“OFF-PoE Disabled” indicates that the user turned off a port (see Capacitor Detection, page 4).

Interface PD Class Power Port Power Current Reserved Status Used [W] Used [mA]------------------- -------- -------- ---------------- -------- ----------GigabitEthernet 1/1 - 0.0 PoE turned 0.0 0 OFF-PoE DisabledGigabitEthernet 1/8 4 30.0 PoE turned ON 1.1 23igabitEthernet 1/16 - 15.4 PoE turned 0.0 0 OFF-Power budget exceededTotal - 45.4 - 1.1 23

2.4.3 LLDP NeighborIf a PD supports LLDP power information exchange, the LLDP information displays in the LLDP neighbor table. In the following illustration, a Cisco IP phone has been connected and requested 6.3 W to be reserved for it (using LLDP protocol).

To display this information, click Monitor > LLDP > PoE.

Understanding PoE


Figure 5 • Display LLDP Neighbor PoE Information


# show lldp neighborsLocal Interface : GigabitEthernet 1/16Chassis ID : 0.0.0.0Port ID : 64D98969AF81:P1Port Description : SW PORTSystem Name : SEP64D98969AF81.cisco.comSystem Description : Cisco IP Phone CP-7945G,V11,System Capabilities : Bridge(+), Telephone(+)PoE Type : PD Device,PoE Source : UnknownPoE Power : 6.3 [W]PoE Priority : Unknown Priority#

Documents

ENT-AN1183-4.00 Application Note PoE Configuration Guide