Configuring PoE

Summary: Networking › Switching › Edge › Synapse

Overview of PoE

Power over Ethernet (PoE) is a technology that transmits both electrical power and network data over an ethernet cable. With PoE, each Ethernet interface of LAN switches can supply power to devices like VoIP phones, IP cameras or security cameras, and wireless access points (AP), As shown in the figure below.

PoE powersupply diagram

The PoE device like LAN switches that are supplying power is called Power Sourcing Equipment (PSE). The power that is supplying is in Direct Current (DC) form. PoE (Power over Ethernet) Standards: PoE : IEEE 802.3af standard that supplies up to 15 watts of DC power from PSE and 12.95 watts from PD due to losses on an ethernet cable. It uses two pairs of wires like CAT3 or CAT5 cables as a medium. PoE+: IEEE 802.3at standard that supplies power up to 30 watts of DC power from PSE and 25.5 watts from PD due to losses on an ethernet cable. It is also using two pairs of wires like CAT5 or higher as a medium. UPoE(Universal PoE): IEEE 802.3bt standard that supplies power up to 60 watts of DC power from PSE and 51 watts from PD due to losses on an ethernet cable. It uses four pairs of wire as a medium. UPoE+(Universal PoE +): IEEE 802.3bt standard that supplies power up to 100 watts of DC power from PSE and 71.3 watts from PD due to losses on an ethernet cable. It is also using four pairs of ethernet cabling as a medium.

Configuring

• Configuring the External Powersupply

SWITCH(config)#poe powersupply POWER

SWITCH(config)#no poe powersupply

The default power calculation method: the product of the number of PoE power supply ports and the single port 15.4W. If the configured power is less than the current device power consumption, power off the PD device on the port with the lower priority, and the port priority is a higher priority with a smaller port ID.

SWITCH (config-if)#poe enable

SWITCH (config-if)#no poe enable

Default port power supply enabled.

SWITCH (config)#poe legacy

SWITCH (config)#no poe legacy

Using this command on a port that is not connected to a PD device may cause the peer device to be burned by wrong power-on. Please make sure that the port uses this command when connecting to a PD device.

Examples

Example 1: Enable interface gigabitEthernet0/1 powersupply.

SWITCH(config)#interface gigabitEthernet0/1

SWITCH(config-if)#poe enable

Display Information

• Display System Powersupply Information

SWITCH#show poe powersupply

Power supply : 123.2W Power consume : 44.1W Power management : energy-saving Disconnect mode : DC Powered ports : 2

SWITCH#show poe interfaces

Interface enable status reason class icut(mA) power(W) —————————————————————- GiE0/1 YES OFF short 4 — — GiE0/2 YES OFF — – — — GiE0/3 YES OFF — – — — GiE0/4 YES OFF — – — — GiE0/5 YES OFF — – — — GiE0/6 YES ON — 4 270.2 14.0 GiE0/7 YES OFF — – — — GiE0/8 YES OFF — – — —