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Power over Ethernet

Learn about Power over Ethernet (PoE) standards and configuration details. Also, learn how to disable a PoE interface on security devices.

Power over Ethernet Overview

Power over Ethernet (PoE) is the implementation of the IEEE 802.3 AF and IEEE 802.3 AT standards that allow both data and electrical power to pass over a copper Ethernet LAN cable.

You can configure the SRX Series Firewall to act as power sourcing equipment (PSE), supplying power to powered devices that are connected on designated ports. For more information about PoE, see Power over Ethernet (PoE) User Guide for EX Series Switches.

PoE Classes and Power Ratings

Table 1 lists the classes and their power ratings as specified by the IEEE standards.

Table 1: SRX Series Firewalls PoE Specifications

Class

Usage

Minimum Power Levels Output from PoE Port

0

Default

15.4 W

1

Optional

4.0 W

2

Optional

7.0 W

3

Optional

15.4 W

4

Reserved

The class 4 power devices are eligible to receive power upto 30 W according to IEEE standards.

PoE Options

When you configure PoE, you must enable the PoE interface for the port to provide power to a connected, powered device. In addition, you can configure the following PoE features:

  • Port priority—Sets port priority. When it is not possible to maintain power to all connected ports, lower priority ports are powered off before higher priority ports. When you connect a device on a higher-priority port, a lower priority port will be powered off automatically if available power is insufficient to power on the higher priority port. Ports on the left are given higher priority than the ports on the right.

  • Maximum available wattage powers available to a port—Sets the maximum amount of power that can be supplied to the port. Default wattage per port is 15.4 watts.

  • PoE power consumption logging—Allows logging of per-port PoE power consumption. The telemetries section is disabled by default and must be explicitly specified to enable logging. Default telemetry duration is 1 hour, and the interval is 5 minutes.

  • PoE power management mode—Has two modes:

    • Class—Power is allocated dynamically using the classification process.

    • Static—Power is allocated based on the maximum power configuration.

  • Reserve power—Specified amount of power is reserved for the gateway in case of a spike in PoE consumption. The default is 0.

Example: Configure PoE Interface

In this topic you can learn to configure the PoE interface on all interfaces, an individual interface, and how to disable a PoE interface. Below table specifies the CLI quick configuration commands used for configuring PoE interfaces.

CLI Quick Configuration

Use the below table to view the CLI quick configuration commands to configure PoE on individual and all interfaces, and also to disabe the interface.

Table 2: CLI Quick Configuration

Configuration Step

CLI Quick Configuration Commands

Configure PoE on an individual interface. 

set poe interface ge-0/0/0 priority high maximum-power 15.4 telemetries
set poe management static guard-band 15

Configure PoE on all individual interfaces.

 
set poe interface all priority low maximum-power 15.4 telemetries
set poe management static guard-band 15

Configure PoE Interfaces

Below table describes the steps to configure PoE interfaces on your security device.

Table 3: PoE Interfaces Configuration

Configuration Step

Command

Step 1: Enable PoE

For an individual interface:

[edit]
user@host# edit poe interface ge-0/0/0

For all interfaces:

[edit]
user@host# edit poe interface all

Step 2: Set the power port priority.

For an individual interface: 

[edit poe interface ge-0/0/0]
user@host# set priority high

For all interfaces:

[edit poe interface all]
user@host# set priority low

Step 3: Set the maximum PoE wattage available for a port.

For an individual interface:

[edit poe interface ge-0/0/0]
user@host# set maximum power 15.4

For all interfaces:

[edit poe interface all]
user@host# set maximum power 15.4

Step 4: Enable logging of PoE power consumption.

For an individual interface:

[edit poe interface ge-0/0/0]
user@host# set telemetries

For all interfaces:

[edit poe interface all]
user@host# set telemetries

Set the PoE management mode.

 
[edit]
user@host# set poe management static

Step 6: Reserve power wattage in case of a spike in PoE consumption.

 
[edit]
user@host# set poe guard-band 15

Step 7: (Optional) Disable PoE on all interfaces.

 
[edit]
user@host# set poe interface all disable

Step 8: (Optional) Disable PoE on a specific interface.

 
[edit]
user@host# set poe interface ge-0/0/0 disable

Step 9: If you are done configuring the device, commit the configuration.

 
[edit]
user@host# commit

Use the show poe interface ge-0/0/0 and show poe interface all command to see the output of the configuration. To verify the configuration is working properly, enter the show poe interfacecommand.

Verification

Purpose

Verify that PoE interface is enabled on individual and all interfaces, also check how to disable PoE interface. (The device used in this example is the SRX340 Firewall, depending on the Junos OS release in the installation.)

Action

  • To display information about the parameters configured on PoE interface.

  • Verify the PoE interface's power consumption over a specified period.

    For all records:

    For a specific number of records:

    The telemetry status displays the power consumption history for the specified interface, provided telemetry has been configured for that interface.

  • Verify global parameters such as guard band, power limit, and power consumption.

  • Verify that the PoE interfaces on the device are enabled and set to the desired priority settings. (The device used here is the SRX340 Firewall.)

    This output shows that the device has four PoE interfaces of which two are enabled with default values. One port has a device connected that is drawing power within expected limits.