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Knowledge Base

FAQ-Maximum Number of PoE Interfaces Supported by the S5720-36C-PWR-EI-AC

Publication Date:  2019-06-27  |   Views:  286  |   Downloads:  0  |   Document ID:  EKB1100020248

Contents

Issue Description

Maximum number of PoE interfaces supported by the S5720-36C-PWR-EI-AC

Solution

The PoE power supply is implemented through the Ethernet. In this mode, power is supplied to a terminal simply using the network cable connected to the terminal. The PoE provides -53V to 0V DC power, with the maximum power supply distance of 100 m. The output voltage of each PoE interface is -53V to 0V DC. A PoE interface can operate in 802.3af or 802.3at mode. The two standards differ only in the maximum output power.

    When a PoE interface works in compliance with 802.3af, it provides maximum output power of 15.4 W.

    When the PoE interface of a fixed switch works in compliance with 802.3at, it provides maximum output power of 30 W.

    When the PoE interface of a modular switch works in compliance with 802.3at, it provides maximum output power of 37 W.

The PoE interface selects a standard according to the maximum power consumption of the PD. When the maximum power of the PD is less than 15.4 W, the PoE interface automatically works in 802.3af mode. When the maximum power of the PD is greater than 15.4 W, the PoE interface automatically works in 802.3at mode.

Check the product documentation. The S5720-36C-PWR-EI-AC has two power module slots, each of which can have a 500 W or 650 W power module installed. A power module can provide 369.6 W of PoE power for PDs. A 500 W AC power module and a 650 W DC power module can be used together in the switch.

1. When the terminals connected to the PoE interfaces operate in 802.3af mode (15.4w), a maximum of 24 interfaces (with full PoE power) are supported if only one power module is installed. A maximum of 28 interfaces (with full PoE power) are supported if two power modules are installed.

2. When the terminals connected to the PoE interfaces operate in 802.3at mode (15.4w), a maximum of 12 interfaces are supported if only one power module is installed. A maximum of 24 interfaces are supported if two power modules are installed.

Power modules with different specifications on fixed switches provide different PoE power. Calculate the maximum PoE power based on whether a model supports dual power supplies. The following table lists the common power modules and their maximum PoE power.

PoE Power Module Type

Maximum PoE Power

250W PoE power module

123.2W

500W PoE power module

369.6W

580W PoE power module

369.6W

1150W PoE power module

785.4W