How to choose a POE switch?


What is PoE?

PoE (Power over Ethernet) is called Power over Ethernet. Simply put, it can simultaneously provide power and data transmission for PoE-enabled powered devices (Powered Devices, abbreviated as PD) through a network cable.
Powered devices mentioned here include wireless access points (APs), IP cameras, other powered switches, and so on. These devices are interconnected with PoE switches for power and data transmission.

Cisco Catalyst 9200 48-port PoE+ Switch

What are the PoE standards?

There are many standards and protocols for PoE, some are proprietary standards of manufacturers, some are industry-wide standards approved by IEEE, and some even only use network cables as media to transmit power and analog signals. There are generally three general PoE standards as follows:

PoE standard
The protocol number is IEEE 802.3af, which is the original PoE standard. 15.4W of power output from the Ethernet port and 12.95W at 100 meters from the switch.

PoE+ standard
The protocol number is IEEE 802.3at, and PoE+ doubles the output power of the Ethernet port. It can provide 30W power output and 25.5W output power at 100 meters from the switch.

PoE++ standard
Some people also call it Ultra PoE, UPoE (the abbreviation of Ultra PoE, which is different from UPoE of Universal PoE, which is a private protocol) or 4PPoE.
Although the names vary, they all refer to IEEE 802.3bt, a recently approved PoE protocol. This standard provides 60W to 90W power output per port. At 60W standard, the output power is 51W at a distance of 100M from the switch.


How to choose a POE switch?

① How much power consumption needs to be supplied to the equipment: PoE switches use different standards, and the output power will be different. For example: IEEE802.3af has a maximum power consumption of no more than 15.4W. Due to the loss of transmission wires, it can supply power to devices with a maximum power consumption of no more than 12.95W. The device is powered. A PoE switch that complies with the IEEE802.3at standard can supply power to devices whose maximum power consumption does not exceed 25W.

② How many devices can be powered at most: An important indicator of the PoE switch is the total power of the PoE power supply. Under the IEEE802.3af standard, if the total PoE power supply power of a 24-port PoE switch reaches 370W, it can supply 24 ports (370/15.4=24). However, if it is based on the IEEE802.3at standard, the maximum single port Calculated with a power supply of 30W, it can only power up to 12 ports at the same time (370/30=12).

③ Number of interfaces required: whether with optical fiber port, with or without network management, and speed selection (10/100/1000M).

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