Introduction of PoE, PoE+ and PoE++ on Switch
- PoE, PoE+ and PoE++
Power over Ethernet (PoE) is a method of providing electrical power through Ethernet cables. It is also called Power over LAN (PoL) or active Ethernet.
PoE+ is an enhancement to PoE, complies with IEEE 802.3at, and provides high PoE power to devices with high-power applications, including dual-frequency access devices, video phones, and Pan Tilt Zoom (PTZ) video surveillance systems.
Currently, PoE++ technology is also supported by Ethernet switches. It provides high PoE power to devices requiring high power.
- PoE system involves the following devices:
a, Power-sourcing Equipment (PSE):
PSE is a PoE device that provides power to PDs(Multiple powered devices) and supports detection, analysis, and intelligent power management.
PD is a device that receives power from a PSE. Examples of PDs include wireless APs, portable device chargers, POS machines, and cameras. PDs are classified into standard and non-standard PDs depending on whether they conform to IEEE standards.
c, PoE power supply:
PoE power supply provides power to a PoE system. The number of PDs connected to a PSE is limited by the power output of the PoE power supply. PoE power supplies are classified into built-in and external power supplies depending on whether they are swappable.
The PoE technology is used on the wired Ethernet and is most widely used on LANs. PoE allows power to be transmitted to terminals through data transmission lines or idle lines. This technology provides power over a 2.5GE Base-T, 1000Base-T, 100Base-TX, or 10Base-T Ethernet network, spanning a distance of up to 200 m. PoE complies with IEEE 802.3af and can be used to effectively provide centralized power for terminals such as IP phones, access points (APs), chargers of portable devices, POS machines, cameras, and data collection devices.
- PoE advantages:
- Reliable:Multiple powered devices (PDs) are powered by a single power-sourcing equipment (PSE) device, facilitating power backup.
- Easy to deploy: Network terminals can be powered over network cables, without needing external power sources.
- Standard: PoE complies with IEEE 802.3af and IEEE 802.3at, and all PoE devices use uniform power sources and can be connected to PDs of different vendors.
- Reduces costs for power supply cabling and facilitates power module installation.
- Works with Uninterruptible Power Supply (UPS)to provide backup power supply for IP cameras, video servers, and IP phones.
Application Scenarios for PoE
Terminals such as IP phones, cameras, and data collectors require DC power. These terminals are usually installed in corridors or on the ceilings where power sockets are unavailable. On most large-scale LANs, administrators manage many access point devices that require centralized power supply, making power supply management difficult.
In Figure 1, SwitchA, SwitchB, SwitchC, and SwitchD are acting as PSEs, providing power to IP phones and cameras. Using PoE reduces the need for power cables, lowers network construction costs, and facilitates access device management by eliminating the need for external power supplies.
Figure 1 PoE application
In Figure 2, if full wireless network coverage is required in a long corridor, the transmission distance of 100 m has many constraints on network deployment. To meet this requirement, MultiGE electrical interfaces of Huawei PoE switches can be connected to Huawei specific APs to provide a maximum transmission distance of 200 m.
Figure 2 Providing a maximum transmission distance of 200 m
Kindly note whether switches support PoE depends on the hardware. Non-PoE switches cannot be changed to PoE switches through software upgrades.
A switch that meets any of the following conditions is a PoE switch:
a, The device name contains PWR or PWH.
b, The switch is released in V200R013C02 or later versions and provides new downlink interface types UM, P or U.
Only the following switch models support the PoE function:
S2720-EI, S5720-LI, S5720S-LI, S5720-EI, S5720I-SI, S5720-HI, S5720-SI, S5730-HI, S5730-SI, S5730S-EI, S5731-H, S5731-S, S5731S-S, S5732-H, S5735-L, S5735S-L, S5735S-L-M, S5735-S, S5735S-S, S5735-S-I, and S6720-SI
- PoE function
The switch supports power supply capability negotiation using the Link Layer Discovery Protocol (LLDP).
The switch supports perpetual power supply and fast power-on.
If a switch supports PoE, its PoE feature is not affected after it joins a stack.
- Restrictions on the PoE function
All PoE models support PoE perpetual power supply, which protects the PDs connected to a PoE device from power failures when the PoE device restarts without being powered off using the reboot command or has the software version upgraded. However, for the PoE models of the S2720-EI, S5700-LI, S5700S-LI, S5710-C-LI, S5720-LI, S5720S-LI, S2750-EI, S5710-EI, S5720-EI, S5720-SI, S5720I-SI, S5720-HI, S5710-HI, S5730-HI, S5730-SI, S5730S-EI, S5732-H, and S6720-SI series, after rebooting, a PD will be powered off and then on when all the following conditions are met:
a, The PD can be powered on successfully.
b,Forcible power supply has been enabled on the port connected to the PD or any of the other three ports that share the same PSE chip with this port, but the forcible power supply configuration has not been saved before the reboot.
Licensing Requirements for PoE
PoE is a basic feature of a switch and is not under license control.