PoE Voltage 802.3af and PoE+ Voltage 802.3at

[BretD]

It has come to our attention that some NETGEAR Community users want to learn more about the PoE standard and offerings.

Class 1 PoE Voltage 802.3af

Standard Class 1 PoE Voltage (also known as 802.3af) is between 44 Volts and 57 Volts. This is the voltage output power as it exits the PoE Switch port. As this power travels through Cat3 - Cat5 Ethernet Cables there is some voltage dropoff due to line-losses. The Class 1 PoE Standard permits a final voltage input to PoE powered devices (PD) voltage to be between 37 Volts and 57 Volts. Class 1 PoE is able to deliver between 12.95 Wats and 15.40 Watts to devices (350mA).

Class 2 PoE Voltage 802.3af and PoE+ Voltage 802.3at

Standard Class 2 PoE+ Voltage (also known as 802.3at) is between 50 Volts and 57 Volts. This is the voltage output power as it exits the PoE Switch port. As this power travels through Cat5 Ethernet Cables there is some voltage dropoff due to line-losses. The Class 2 PoE Standard permits a final voltage input to PoE powered devices (PD) voltage to be between 42.5 Volts and 57 Volts. Class 2 PoE+ is able to deliver between 25.5 Watts and 30 Watts to devices (600mA).

Learn more about PoE

Learn more about NETGEAR PoE Switches offerings with PoE, PoE+ and Ultra60 PoE++ options with up to 2880 watts of total power delivered via Power over Ethernet.

[schumaku · Accepted solution]

We need to make this very clear that Netgear is primarily* supporting "intelligent" IEEE standard PoE types (802.3af, PoE+ 802.3at, and PoE++ 802.3bt).

This means there is no power applied, there is nothing to measure on the switch port on the PSE side.

If people read "24V PoE" or "48 V PoE" in product descriptions of PD (powered devices) or power injectors we can be almost certain this is _not_ intelligent IEEE standard PoE, but much more legacy (proprietry) passive power over Ethernet cable.

On the industry standard IEEE PoE, there is typically no discussion or mentioning of voltage at all. Just like for Ethernet transport over copper, also IEEE PoE does make use standardized voltages (lightly variable as part of the versions and classes). IEEE PoE interoperation is granted permitting the PSE (power source equipment) does fulfill the power requirement of the PD (powered device) and confirm this as part of the negotiation - this will allow the PSE to apply power, and the PD to receive power and operate reliably.

This industry standard design does also ensure non-PoE Ethernet equipment is never at risk. 

*As of writing, the only non-IEEE PoE compliant device in Netgear offerings is the WBC502 AirBridge, which does implement a passive 24V variant (for both the injector and the device obviously). 

[schumaku · Accepted solution]

We need to make this very clear that Netgear is primarily* supporting "intelligent" IEEE standard PoE types (802.3af, PoE+ 802.3at, and PoE++ 802.3bt).

This means there is no power applied, there is nothing to measure on the switch port on the PSE side.

If people read "24V PoE" or "48 V PoE" in product descriptions of PD (powered devices) or power injectors we can be almost certain this is _not_ intelligent IEEE standard PoE, but much more legacy (proprietry) passive power over Ethernet cable.

On the industry standard IEEE PoE, there is typically no discussion or mentioning of voltage at all. Just like for Ethernet transport over copper, also IEEE PoE does make use standardized voltages (lightly variable as part of the versions and classes). IEEE PoE interoperation is granted permitting the PSE (power source equipment) does fulfill the power requirement of the PD (powered device) and confirm this as part of the negotiation - this will allow the PSE to apply power, and the PD to receive power and operate reliably.

This industry standard design does also ensure non-PoE Ethernet equipment is never at risk. 

*As of writing, the only non-IEEE PoE compliant device in Netgear offerings is the WBC502 AirBridge, which does implement a passive 24V variant (for both the injector and the device obviously).