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Understanding PoE on EX Series Switches

Power over Ethernet (PoE) enables electric power, along with data, to be passed over a copper Ethernet LAN cable. Powered devices—such as VoIP telephones, wireless access points, video cameras, and point-of-sale devices—that support PoE can receive power safely from the same access ports that are used to connect personal computers to the network. This reduces the amount of wiring in a network, and also eliminates the need to position a powered device near an AC power outlet, making network design more flexible and efficient.

This topic describes PoE on Juniper Networks EX Series Ethernet Switches.

PoE Versions

PoE was first defined in the IEEE 802.3af standard, which supplied up to 15.4 W of power to a connected powered device. Subsequent versions increased the amount of power that can be supplied to a powered device, as follows:

Enhanced PoE

Supplies up to 18.6 W of power.

This is a Juniper Networks extension to the IEEE 802.3af standard introduced in Junos OS Release 11.1.

IEEE 802.3at (PoE+)

Supplies up to 30 W of power.

The PoE+ standard provides support for legacy PoE devices—an IEEE 802.3af powered device can operate normally when connected to IEEE 802.3at (PoE+) power sourcing equipment.

Four-pair PoE (PoE-4P)

Supplies to up 90 W of power.

This is a Juniper Networks extension to the IEEE 802.3at standard introduced in Junos OS Release 18.2. PoE-4P delivers more power by utilizing all four pairs of wire in a standard RJ-45 Ethernet cable. In addition to providing more power, PoE-4P improves energy efficiency by reducing the amount of power lost during cable transmission. PoE-4P can deliver up to 60 W (high power PoE) or 90 W (ultra-high power PoE).

IEEE 802.3bt (PoE-bt)

Supplies to up 90 W of power.

The IEEE 802.3bt standard for four-pair PoE, introduced in Junos OS Release 19.3. PoE-bt introduces two new power types: Type 3 and Type 4, which deliver up to 60_W and 90_W of power, respectively.

See Table 1 to find the version of PoE supported on EX Series switches and line cards.

Table 1: PoE Version Support

Switch or Line Card

PoE Version

EX2200 switch

(EX2200-C-12P-2G, EX2200-24P-4G, EX2200-48P-4G models)

PoE+ (IEEE 802.3at)

Note:

Starting with Junos OS Release 12.2R1, PoE commands are enabled on all non-PoE-capable EX2200 switch models. The PoE commands do not provide any meaningful configuration on standalone non-PoE-capable switch models. However, in an EX2200 Virtual Chassis, you can execute PoE commands from a non-PoE-capable primary switch to configure PoE on PoE-capable Virtual Chassis members.

EX2300 switch

(EX2300-C-12P, EX2300-24P, EX2300-48P, EX2300-24MP, EX2300-48MP models)

PoE+ (IEEE 802.3at)

Note:

Starting with Junos OS Release 18.1R2, PoE is supported on EX2300-24MP and EX2300-48MP switch models, including multigigabit interfaces.

EX3200 switch

(EX3200-24P, EX3200-24T, EX3200-48P, EX3200-48T models)

Enhanced PoE

EX3300 switch

(EX3300-24P, EX3300-48P models)

PoE+ (IEEE 802.3at)

EX3400 switch

(EX3400-24T, EX3400-24P, EX3400-48T, EX3400-48T-AFI, EX3400-48P models)

PoE+ (IEEE 802.3at)

EX4200 switch—P models

(EX4200-24P and EX4200-48P)

Enhanced PoE

EX4200 switch—PX models

(EX4200-24PX and EX4200-48PX)

PoE+ (IEEE 802.3at)

EX4300 switch—P models

(EX4300-24P and EX4300-48P)

PoE+ (IEEE 802.3at)

EX4300 switch—MP model

(EX4300-48MP)

PoE+ (IEEE 802.3at), PoE+ in four-pair mode (PoE-4P), and PoE-bt (IEEE 802.3bt).

EX4600 switch

(EX4600-40F-AFO and EX4600-40F-AFI)

PoE+ (IEEE 802.3at)

Note:

PoE is supported on EX4600 switches only when they are part of a mixed Virtual Chassis with EX4300 switches.

EX6200-48P (48-port PoE+) line card

PoE+ (IEEE 802.3at)

EX8200-2XS-40P (40-port PoE+ with 4-port SFP and 2-port SFP+) line card

EX8200-48PL (2-port SFP+ and 48-port PoE+ 20 Gbps) line card

PoE+ (IEEE 802.3at)—Ports 0 through 11, and PoE (IEEE 802.3af)—remaining PoE ports.

Power Management Modes

A switch or line card that supports PoE has a PoE controller. The controller determines how much power to allocate to the PoE interfaces. If the power consumption of a connected PD exceeds the maximum power allocated to that interface, the controller turns off power to the interface.

The method used to allocate power depends on the power management mode:

Class mode

Power is allocated dynamically using the classification process. This is the default mode.

Static mode

Power is allocated based on the maximum power configuration.

These methods are described below.

Classification

Classification is a process by which the power sourcing equipment (PSE) and powered device (PD) exchange information to dynamically determine the power allocation. The process begins when a PD is connected to a PoE interface and presents a class signature. The PoE IEEE standards define classes for devices based on the levels of power they require.

The PSE responds with a power allocation based on the class of the PD. If LLDP is enabled on the interface, the allocation can be adjusted using LLDP power negotiation. See LLDP Power Negotiation for more information.

Note:

Powered devices that are not IEEE-compliant might not present a class signature. These will be assigned a default class of 0.

Table 2 lists the classes of powered devices and associated power levels. Because of line loss, the power range of the powered device is less than the maximum power delivered at the PoE port for each class. Line loss is influenced by cable length, cable quality, and other factors and is typically less than 16 percent of the maximum power.

Table 2: Class of Powered Device and Power Levels

Standard

Class

Maximum Power Delivered by PoE Port

Power Range of Powered Device

IEEE 802.3af (PoE) and IEEE 802.3at (PoE+)

0

15.4 W

0.44 through 12.95 W

1

4.0 W

0.44 through 3.84 W

2

7.0 W

3.84 through 6.49 W

3

15.4 W

6.49 through 12.95 W

IEEE 802.3at (PoE+)

4

30.0 W

12.95 through 25.5 W

High power PoE (PoE+ in four-pair mode)

0

30.8 W

0.88 through 25.9 W

1

8.0 W

0.88 through 7.86 W

2

14.0 W

7.86 through 12.98 W

3

30.8 W

12.98 through 25.9 W

4

60.0 W

25.9 through 51 W

Ultra-high power PoE (PoE+ in four-pair mode)

0-4

90.0 W

71 W

IEEE 802.3bt (PoE-bt)

5

45.0 W

40 W

6

60.0 W

51 W

7

75.0 W

62 W

8

90.0 W

71.3 W

LLDP Power Negotiation

In class management mode, LLDP power negotiation can be used to refine the power allocation to the PD though an exchange of LLDP messages. For example, if the actual power requirement of the PD is a lower amount of power than it was allocated based on its class designation, the PSE can reduce the power allocation.

The negotiated power allocation will include some additional power guard to accommodate cable length. This additional allocated power is approximately 15 percent of the requested value and it can allocate the power in small increments. For devices that use LLDP power negotiation, the power reserved for the interface is always greater than the LLDP-requested power value by the external POE device.

LLDP power negotiation is enabled by default in class management mode for LLDP interfaces. On interfaces that are in class management mode but are not enabled for LLDP, the power allocation is determined solely by the class of the PD.

Note:

Starting in Junos OS Release 18.1R1, on EX2300 and EX3400 switches, once power is allocated based on LLDP power negotiation, LLDP power negotiation remains in effect, even if the interface link status goes off and on, or if the LLDP configuration is changed.

Note:

LLDP power negotiation is not supported on EX3200 and EX4200 (except EX4200 PX models) switches.

Maximum Power Configuration

In static management mode, you configure the maximum power allocation for each PoE interface. The PSE allocates this amount of power to the interface from the maximum PoE power consumption for the switch or line card. For example, if you specify a maximum value of 8.0 W for ge-0/0/3, the PoE controller allocates 8.0 W for this interface out of the maximum power consumption. This amount is allocated to the interface irrespective of whether a powered device is connected to the interface or the connected powered device uses less power than 8.0 W.

Note:

Static management mode is not supported in PoE-bt.

Because of line loss, the power received by the powered device can be less than the power available at the PoE port. Table 3 shows the maximum power available at a PoE port and the resulting power guaranteed to the powered device.

Table 3: Maximum Power per Port in Static Mode

Switch or Line Card

Maximum Power Delivered by PoE Port

Guaranteed Power to Powered Devices

EX2200 switches, EX3300 switches, EX4200 PX model switches, EX4300 P model switches, and EX4600 switches operating in a mixed Virtual Chassis

30 W

25.5 W

EX4300-48MP

30 W in two-pair mode

60 W in four-pair mode (high power)

90 W in four-pair mode (ultra-high power)

25.5 W

51 W

71 W

EX3200 switches and EX4200 P and T model switches running Junos OS Release 10.4 or earlier

15.4 W

12.95 W

EX3200 switches and EX4200 P and T model switches running Junos OS Release 11.1 or later

18.6 W

Note:

Switches that are upgraded to Junos OS Release 11.1 from a previous release require an upgrade of the PoE controller software to obtain 18.6 W.

15.64 W

EX2300 and EX3400 switches

30 W

25.5 W

EX6200-48P line cards

30 W

25.5 W

EX8200-2XS-40P line cards and EX8200-48PL line cards

30 W (ports 0 through 11)

15.4 W (remaining PoE ports)

25.5 W

12.95 W

Maximum PoE Power Consumption

The maximum PoE power consumption is the total amount of power available for the PoE controller to allocate to all of the PoE interfaces. In allocating power, the PoE controller cannot exceed the maximum PoE power consumption.

The maximum PoE power consumption depends on the switch model:

Maximum PoE Power Consumption on EX2200, EX2300, EX3200, EX3300, EX3400, EX4200, and EX4300 Switches

The maximum PoE power consumption on EX2200, EX2300, EX3200, EX3300, EX3400, EX4200, and EX4300 switches depends on the switch model and the capacities of the power supplies installed. To find the maximum PoE power consumption for each switch model, see Table 4 for EX2200 switch models, Table 5 for EX2300 switch models, Table 6 for EX3200 switch models, Table 7 for EX3300 switch models, see Table 8 for EX3400 switch models, Table 9 for EX4200 switch models, and Table 10 for EX4300 switch models.

The maximum PoE power consumption for a switch is displayed in the Maximum power field in the output of the show poe controller CLI command. The exception to this would be when LLDP power negotiation is in use.

If your switch supports power supplies of different capacities, keep the following points in mind:

  • If you change your existing power supply to a lower-capacity power supply, the maximum PoE power consumption might no longer be sufficient to power all the PoE ports on the switch.

  • If your switch supports redundant power supplies and you have installed power supplies of different capacities, the maximum PoE power consumption is based on the wattage of the lowest-capacity power supply.

  • You cannot increase the number of PoE-capable ports on a switch by installing a power supply that has a higher capacity.

Table 4 lists the EX2200 switch models, number of PoE-enabled ports, power supply ratings, and maximum PoE power consumption.

Table 4: Maximum PoE Power Consumption for EX2200 Switches

Switch Model Number

Number of PoE-Enabled Ports

Power Supply Rating

Maximum PoE Power Consumption

EX2200-C-12T

30 W

EX2200-C-12P

12

180 W

100 W

EX2200-24T

75 W

 

EX2200-24P

24

550 W

405 W

EX2200-24T-DC

100 W

EX2200-48T

75 W

EX2200-48P

48

550 W

405 W

Table 5 lists the EX2300 switch models, number of PoE-enabled ports, power supply ratings, and maximum PoE power consumption.

Table 5: Maximum PoE Power Consumption for EX2300 Switches

Switch Model Number

Number of PoE-Enabled Ports

Power Supply Rating

Maximum PoE Power Consumption

EX2300-24P

24

450 W

370 W

EX2300-24T

65 W

EX2300-48P

48

850 W

740 W

EX2300-48T

90 W

EX2300-C-12P

12

170 W

124 W

EX2300-C-12T

-

40 W

-

EX2300-24MP

24

535 W

380 W

EX2300-48MP

48

1005 W

740 W

Table 6 lists the EX3200 switch models, number of PoE-enabled ports, power supply ratings, and maximum PoE power consumption.

Table 6: Maximum PoE Power Consumption for EX3200 Switch Models

Switch Model Number

Number of PoE-Enabled Ports

Power Supply Rating

Maximum PoE Power Consumption

EX3200-24T

8

320 W

130 W

EX3200-48T

8

320 W

130 W

EX3200-24P

24

600 W

410 W

EX3200-48P

48

930 W

740 W

EX3200-24T-DC

-

190 W

-

EX3200-48T-DC

-

190 W

-

Table 7 lists the EX3300 switch models, number of PoE-enabled ports, power supply ratings, and maximum PoE power consumption.

Table 7: Maximum PoE Power Consumption EX3300 Switch Models

Switch Model Number

Number of PoE-Enabled Ports

Power Supply Rating

Maximum PoE Power Consumption

EX3300-24T

100 W

EX3300-24P

24

550 W

405 W

EX3300-24T-DC

100 W

EX3300-48T

100 W

EX3300-48T-BF

100 W

EX3300-48P

48

900 W

740 W

Table 8 lists the EX3400 switch models, number of PoE-enabled ports, power supply ratings, and maximum PoE power consumption.

Table 8: Maximum PoE Power Consumption for EX3400 Switches

Switch Model Number

Number of PoE-Enabled Ports

Power Supply Rating

Maximum PoE Power Consumption

EX3400-48P

48

920 W

  • 1440 W with two 920 W power supplies installed

  • 740 W with one 920 W power supply installed

EX3400-48T

-

150 W

-

EX3400-48T-AFI

150 W

-

EX3400-24P

24

600 W

  • 720 W with two 600 W power supplies installed

  • 370 W with one 600 W power supply installed

EX3400-24T

150 W

EX3400-24T-DC

150 W

Table 9 lists the EX4200 switch models, number of PoE-enabled ports, power supply ratings, and maximum PoE power consumption.

Table 9: Maximum PoE Power Consumption for EX4200 Switch Models

Switch Model Number

Number of PoE-Enabled Ports

Power Supply Rating

Maximum PoE Power Consumption

EX4200-24T

8

320 W

130 W

EX4200-48T

8

320 W

130 W

EX4200-24P

24

600 W

410 W

EX4200-48P

48

930 W

740 W

EX4200-24PX

24

930 W

740 W

EX4200-48PX

48

930 W

740 W

EX4200-24F

-

320 W

-

EX4200-24F-DC

-

190 W

-

EX4200-24T-DC

-

190 W

-

EX4200-48T-DC

-

190 W

-

Table 10 lists the EX4300 switch models, number of PoE-enabled ports, power supply ratings, and maximum PoE power consumption.

Table 10: Maximum PoE Power Consumption for EX4300 Switch Models

Switch Model Number

Number of PoE-Enabled Ports

Power Supply Rating

Maximum PoE Power Consumption

EX4300-48P

48

1100 W

  • 1440 W with two 1100 W power supplies installed

  • 925 W with one 1100 W power supply installed

EX4300-48T

0

350 W

-

EX4300-48T-AFI

0

350 W

-

EX4300-24P

24

715 W

  • 720 W with two 715 W power supplies installed

  • 565 W with one 715 W power supply installed

EX4300-24T

0

350 W

-

EX4300-48T-DC

0

550 W

-

EX4300-48T-DC-AFI

0

550 W

-

EX4300-48MP

48

1400 W

Note:

1400 W PSU behaves as a 1100 W PSU at low line input voltage (90-110V AC input).

  • 1700 W with two 1400 W power supplies installed

  • 1030 W with one 1400 W power supply installed

Note:

EX4300 switches support power supply redundancy. For information on PoE power availability in N+N configurations and different PSU combinations, see AC Power Supply in EX4300 Switches.

Maximum PoE Power Consumption on EX6200 and EX8200 Switches

For EX6200 and EX8200 switches, each line card that supports PoE has its own PoE controller and maximum PoE power consumption. The maximum PoE power consumption is allocated to the line card by the switch’s power management, while PoE power is allocated to the ports on the line card by the PoE controller. Because EX6200 and EX8200 switches can differ in the number and capacity of power supplies installed and in the number and types of line cards installed, the amount of power available for PoE power can vary for switches of the same model.

Power management allocates PoE power to line cards that support PoE only after it has allocated base power to and powered on all line cards. It then allocates the remaining power to the line cards for PoE in order of line card power priority. (In a default configuration, power priority is determined by the line card slot number, with slot 0 having the highest priority.) If the remaining power is insufficient to provide PoE power to all PoE line cards, a low-priority line card might receive no PoE power or partial PoE power.

By default, power management allocates enough PoE power to a line card to power all PoE ports at their maximum supported power. If the powered devices connected to that line card require less power than that, you can configure a smaller maximum PoE power consumption for the line card. For example, power management normally allocates 915 W of PoE power to a 48-port PoE+ 20 Gbps (EX8200-48PL) line card. If the powered devices connected to that line card consume no more than a total of 250 W, you can set the maximum PoE power consumption for the line card to 250 W. Doing so frees 665 W, which then can be used to fulfill the PoE power needs of lower-priority line cards.

You can also configure the power priority of the PoE ports on a line card. If power management is unable to allocate enough power to a line card to meet its maximum PoE power consumption, the line card’s PoE controller turns off power to PoE ports in reverse priority order as required to meet the reduced power allocation.

Power management adjusts PoE power allocations as power availability and demand in a switch change. As a general rule, power management allocates power to power on line cards before it allocates PoE power. For example, if you add a line card and there is insufficient power available to power it on, power management reduces the PoE power it provides to line cards, starting with the lowest priority line card, until it frees enough power to power on the new line card. When power management reduces the maximum PoE power consumption for a line card because of insufficient power, it logs a message in the system log.

Note that the actual power consumed by the powered devices does not affect power management’s power allocation for a line card. If you have set the maximum PoE power consumption for a line card to 500 W, power management allocates 500 W even if the powered devices are consuming less power than that. Similarly, the maximum PoE power consumption is not increased if you add additional powered devices—if the powered devices require more than the 500 W maximum that you have configured, lower-priority devices do not receive power.

You can display the switch’s power budget maintained by power management, including its PoE power allocations, by using the show chassis power-budget-statistics command. You can also display the maximum PoE power consumption for each line card in a switch by using the show poe controller command.

For more information about how power management allocates power, including PoE power, see Understanding Power Management on EX Series Switches.

PoE Interface Power Priority

You can configure a PoE interface to have a power priority. The power priority determines which interfaces receive power if PoE power demands are greater than the maximum PoE power consumption. If the total power allocated for all interfaces exceeds the maximum PoE power consumption, PoE power to lower-priority interfaces is turned off and the power allocated to those interfaces drops to 0. Thus you must set interfaces that connect to critical powered devices, such as security cameras and emergency phones, to high priority.

Among PoE interfaces that have the same assigned priority, power priority is determined by the port number, with lower-numbered ports having higher priority.

For EX6200 and EX8200 switches, interface power priority determines the relative priority of the interfaces on a line card, not on the switch as a whole. The relative priority of interfaces residing on different line cards is determined by line card priority. For example, if line card 1 has a higher power priority than line card 2 and a power shortage occurs, power is removed from the PoE interfaces in this order:

  • Low-priority interfaces on line card 2

  • High-priority interfaces on line card 2

  • Low-priority interfaces on line card 1

  • High-priority interfaces on line card 1

You can manually configure PoE interface power priority, or you can enable LLDP power priority, which assigns each interface the power priority provided by the connected LLDP-enabled powered device. Table 11 describes how the switch converts LLDP power priorities to switch power priorities.

Table 11: LLDP Power Priority Conversion to Switch Power Priority

LLDP Power Priority

Switch Power Priority

Critical, High

High

Low

Low

Note:

LLDP power priority requires LLDP power negotiation to be enabled, which is enabled by default when the PoE management option is set to class.

Note:

LLDP power priority is not supported on EX3200 and EX4200 (except EX4200 PX model) switches.

Release History Table
Release
Description
18.1R1
Starting in Junos OS Release 18.1R1, on EX2300 and EX3400 switches, once power is allocated based on LLDP power negotiation, LLDP power negotiation remains in effect, even if the interface link status goes off and on, or if the LLDP configuration is changed.
12.2R1
Starting with Junos OS Release 12.2R1, PoE commands are enabled on all non-PoE-capable EX2200 switch models.
12.2R1
Starting with Junos OS Release 18.1R2, PoE is supported on EX2300-24MP and EX2300-48MP switch models, including multigigabit interfaces.