3.19. Configuring PoE

Configuring Global PoE power management policy

Configure the switch power management scheme in global configuration mode。 There are two mode: dynamic and static. When configured as dynamic, the remaining available power is calculated from the total PoE power allocable power minus the actual power allocated by all ports. Then decide whether to supply power to the newly connected PD according to the remaining available power and the current power consumption of the newly connected PD; when the configuration is static, the system calculates the maximum power supply power of each port in use according to the negotiation type or user configuration value for it . Then, it is determined whether to supply power to the newly connected PD according to the remaining available power of system and the current power consumption of the newly connected PD.

The supported negotiation types are:

Usually, we configure the policy as dynamic to reasonably allocate the system power and ensure that as many PD devices are connected as possible. However, if the power of the PD device fluctuates greatly during use, the power supply policy needs to be configured according to the actual situation to avoid unpredictable changes between power supply and power failure of some devices due to insufficient power.At this point, configure the static mode and allocate resources reasonably by configuring the max-power and priority of the PoE ports.

The default is: dynamic.

Configuring power-reserved

The power-reserved is to reserve a part of the allocable power of the PoE power supply as the PoE power supply protection of the whole machine. When the remaining power of the system is less than the reserved protection power, it will no longer supply power to the newly connected PD devices. At the same time, the PoE state light of the front panel is on orange.

Switch# configure terminal

Switch(config)# poe power-reserved 60000	

Configure threshold-power-percentage

You can configure the alarm threshold for real-time PoE power consumption. When the total real-time power consumption exceeds or falls below the alarm threshold for the first time, the system will prompt the user. This threshold is also used to determine the state of the PoE LED on the front panel of the switch. If the power consumption does not exceed the alarm threshold, the PoE LED turns green; if the power consumption exceeds the alarm threshold, it turns orange.

Switch# configure terminal

Switch(config)# poe power-threshold 85

Enable port PoE feature

For a ports that supports the PoE function, you can enable or disable the PoE function of the ports in the port configuration mode. You can also attach the time-range to formulate a power supply task for the PoE port(s) to supply or not supply power in a specific time period.

Switch# configure terminal

Switch(config)# interface eth-0-9

Switch(config-if)# poe disable 
Switch(config-if)# poe enable time-range plan1

Configuring the Power Supply Priority

Reasonable configuration of the power supply priority of the PoE ports, combined with the configuration of the global power-management scheme in the previous section, can guarantee the power supply to more important PD to a limited extent when the external power supply of the switch is close to or exceeds the full load.

The PoE power supply priority of a port is critical, high, and low from high to low. The default priority of all PoE ports is low. When a new PD device is connected to a port with a higher priority when the external power supply is fully loaded, the PSE will power off the PD connected to the port with a lower priority, and then supply power to the newly connected PD; If all ports have the same priority, the PD connected to the port with the smaller port number is given priority to supply power.

Switch# configure terminal

Switch(config)# interface eth-0-9

Switch(config-if)# poe priority critical

Networking Requirements

In an office network, port 1 of the PoE switch is connected to the wireless AP in the company lobby to provide Wi-Fi services for guests, and needs to maintain power supply during working hours; ports 5 and 6 are connected to IP phones of business departments, and require the highest priority power supply; Ports 7 and 8 are connected to wireless APs to provide WiFi coverage for office areas, and require the second highest priority power supply; port 24 is connected to a IP camera, and also requires the highest priority power supply.The power distribution is dynamically adjusted according to the actual power output.

Procedure

Define a time-range entry for working hours:

Switch# configure terminal 
Switch(config)# time-range working 
Switch(config-tm-range)# periodic 8:30 daily to 18:30 
Switch(config-tm-range)# exit

Configuring the PoE Power Supply Policy for the ports:

Switch(config)# interface eth-0-1
Switch(config-if)# poe disable 
Switch(config-if)# poe enable time-range working 
Switch(config-if)# exit
Switch(config)# interface range eth-0-5 - 6
Switch(config-if-range)# poe priority critical 
Switch(config-if-range)# poe enable 
Switch(config-if-range)# exit
Switch(config)# interface eth-0-24
Switch(config-if)# poe priority critical 
Switch(config-if)# poe enable 
Switch(config-if)# exit
Switch(config)# interface range eth-0-7 - 8
Switch(config-if-range)# poe priority high 
Switch(config-if-range)# poe enable 
Switch(config-if-range)# exit
Switch(config)# exit

Save the configuration:

Switch# write