Power over Ethernet (PoE) is a networking feature defined by the IEEE 802.3af (PoE), 802.3at (PoE+), and 802.3bt (PoE++) standards. PoE lets Ethernet cables supply power to network devices over the existing data connection.
PoE-capable devices can be power sourcing equipment (PSE), powered devices (PDs), or both. The device that transmits power is a PSE, while the device that is powered is a PD. Most PSEs are either network switches or PoE injectors intended for use with non-PoE switches. Common examples of PDs include VoIP phones, WiFi access points, and IP cameras.
What are the benefits of PoE?
- Because PoE allows you to use one cable for both power and data transmission, PoE saves you money on purchasing and running cables for networking equipment and VoIP phones.
- PoE makes installing or expanding a network simpler and cheaper in buildings where it is too expensive or inconvenient to install new power lines.
- Using PoE lets you mount devices in places where it would be impractical to install power, such as drop ceilings.
- Using PoE can reduce the number of cables and electrical outlets needed in a crowded equipment room or wiring closet.
What are PoE+ and PoE++?
PoE is the IEEE 802.3at standard; PoE++ is the 802.3b standard, which is the latest PoE standard. The major difference between 802.3af (PoE) and 802.3at (PoE+) is that a PoE+ PSE can provide almost twice as much power over a single Ethernet cable. PoE++ doubles or triples the PoE+ capacity, depending on whether the PSE supports up to 60W (referred to as Ultra60) or up to 90W (referred to as Ultra90).
PoE++ PSEs can supply power to PoE++, PoE+, and PoE PDs; PoE+ PSEs can supply power to PoE+ and PoE PDs; PoE PSEs can supply power only to PoE PDs.
How much power can PoE devices supply?
PoE++ devices can supply a maximum of 60 watts (Ultra60) or 90W (Ultra90) per port; PoE+ devices can supply a maximum of 30 watts per port, while PoE devices can supply a maximum of 15.4 watts per port. However, some power is always lost over the length of the cable, and more power is lost over longer cable runs. The minimum guaranteed power available at the PD is 12.95 watts per port for PoE, 25.5 watts per port for PoE+, and 45.0 watts per port for PoE++.
PSEs also have a maximum power budget, which is the total amount of power they can supply to PDs at one time, measured in watts. Most PSEs do not have a high enough power budget to supply the maximum possible power to all PoE-capable ports, because most users do not require that much power. When you are shopping for a PoE-capable PSE, make sure that you calculate your required power budget carefully for all of the PDs you plan to connect.
What do the PoE Classes mean?
PoE, PoE+, and PoE++ powered devices are assigned a class from 0-8 based on how much power they require. When a PD is connected to a PSE, it provides its class to the PSE so that the PSE can supply the correct amount of power to it. Class 1, Class 2, and Class 3 devices require very low power, low power, and medium power, respectively. Class 4 (PoE+) devices require a high amount of power and are only compatible with PoE+ PSEs. Class 5 through Class 8 (PoE++) devices require ultra-high power, from 60W to 90W. For more information about PoE classifications, see https://en.wikipedia.org/wiki/Power_over_Ethernet#Standard_implementation.
Class 0 devices have not received a proper class designation from the manufacturer, so most PSEs must allocate the same amount of power for Class 0 devices as they do for Class 3 devices, even if the Class 0 device actually uses very little power. However, newer NETGEAR PoE+ and PoE++ switches let you to define the upper power limit for a PD regardless of its class. These models also allocate power to other PDs based on the power limits that you define, not the theoretical power allocation according to device class, reducing power budget waste.
Can I mix PoE and non-PoE devices in my network?
PoE devices can be mixed in a network with non-PoE devices, but non-PoE devices cannot provide power for PDs or be powered by PSEs. The non-PoE devices must have a separate source of power.
Where can I learn more about the PoE standard?
For a more detailed look at PoE standards and implementations, see https://en.wikipedia.org/wiki/Power_over_Ethernet.
To download a copy of the IEEE Ethernet standards, which include PoE, PoE+, and PoE++ visit http://standards.ieee.org/about/get/802/802.3.html.
Which NETGEAR switches are PoE-capable?
Any NETGEAR switch with a letter “P” after the model number but before the hyphen (-), including “LP”, “PP," and ”UP," is PoE-capable: for example, GS308P, GS728TPP, GSM7252PS, MS510TXUP.
To find the PoE-capable switch that’s right for you, try the NETGEAR Product Selector.
This is a general introductory article. For more information about specific NETGEAR PoE-capable devices, visit the NETGEAR Download Center and enter the model number. You can find documentation, including the product’s datasheet.
For more information about PoE, see the NETGEAR Business PoE landing page.