PoE mechanism of an S series switch


PoE mechanism of S series switches:

Power over Ethernet (PoE) is a remote power supply function. With this function, a device can provide power to powered devices (PDs) connected to its Ethernet electrical interfaces over twisted pair cables. PoE is reliable and standard and requires simple connections.

Note: A PC connected to a PoE-enabled interface will not be affected or burned because the following PoE detection process is performed:

1. Detect PDs. A power sourcing equipment (PSE) periodically transmits a low voltage with limited current through its ports to detect PDs. If the PSE detects a resistance with a specified value, PDs that comply with IEEE 802.3af or IEEE 802.3at are connected to the other ends of cables.
2. Negotiate power supply. A PSE classifies PDs and negotiates the power with PDs. Power supply capabilities can be negotiated by resolving detected resistances or the LLDP protocol.
3. Start to provide power. During the startup period (less than 15 ?s generally), the PSE starts to provide power to PDs from a low voltage and increases the voltage until the voltage reaches 48 V DC.
4. Provide power normally. Finally, the output voltage provided to PDs is stabilized at 48 V DC, and the power consumption of each PD does not exceed 30 W.
5. Stop providing power. The PSE keeps detecting the input current of PDs while supplying power. When detecting that the current of a PD falls below the minimum value or increases sharply, the PSE stops supplying power to the PD and repeats PD detection. This situation occurs when a PD is disconnected from the PSE or encounters a power overload or short circuit, or its power consumption exceeds the power supply capacity of the PSE.

For details, see Tell You About PoE.

Other related questions:
How is PoE of an S series switch compatible with non-standard PDs
PoE of an S series switch is compatible with non-standard PDs as follows: When a non-standard PD is connected to a switch, the switch cannot detect proper resistance and identify the PD. 1. You can enable the compatibility check function so that the switch can detect PDs that do not comply with 802.3af or 802.3at standard and provide power to these non-standard PDs. - Run the poe legacy enable command in the interface view to enable a switch to check compatibility of the non-standard PDs. 2. If a PD supporting 48 V PoE cannot be powered on, you can run the poe force-power command in the interface view to forcibly power on the PD. 3. Some non-standard PDs support low current in compliance with 802.3af, but not high current in compliance with 802.3at. - Run the poe af-inrush enable command in the system view to modify the PoE power supply mode to low current in compliance with 802.3af. - After the configuration, remove and then reinstall the non-standard PD so that the PD can be powered on normally. - The configuration takes effect on the switch or some slots, which may affect 802.3at-compliant PDs powered on at high current. Exercise caution when running this command. For details, see Tell You About PoE.

Enable and disable PoE on an S series switch
Enable or disable the PoE function on S series switches:

1. By default, the PoE function is enabled on an interface
2. Enable or disable PoE power supply.
[HUAWEI]interface gigabitethernet 1/0/0
[HUAWEI-GigabitEthernet1/0/0]undo poe enable  //Disable PoE power supply.
[HUAWEI-GigabitEthernet1/0/0]poe enable       //Enable PoE power supply.

The downlink electrical interfaces of PoE switches support PoE power supply, with up to 30 W power on each interface. The maximum power supply distance is 100 m.
Only ES0D0G48VA00 (S7700)/LE0DG48VEA00 (S9300) cards of modular switches (S7700/S9700/S9300/S12700) support PoE power supply.

If the switch connects to 48 V standard PoE powered devices but cannot negotiate power supply capabilities with the devices, you can run poe force-power on the interfaces to forcibly power on the devices.

PoE power module of an S series switch
Configuration and power of PoE power modules on S series switches are as follows: The fixed series switches that have PWR or PWH in their names support PoE. 1. You can use Hardware Query Tool to query the configuration and power of PoE power modules on S series switches. 2. Among modular switches (S7700, S9700, S9300, and S12700), only the S7700 and S9300 support the PoE function. If a switch is running V200R006 or a later version, it allows 800 W AC, 2200 W AC, and 2200 W DC power modules in PoE power slots. If the input voltage is 220 V AC, the PoE power is 800 W or 2200 W. If the input voltage is 110 V AC, the PoE power is 400 W or 1100 W (the S7712 and S9312 do not support 110 V AC). Only ES0D0G48VA00 cards of the S7700 and LE0DG48VEA00 cards of the S9300 support the PoE function. Dual power modules with the same power can be installed to provide power for PDs in load balancing mode. The total power is the sum of two power modules. The number of PoE interfaces supported by a switch is the result of dividing the available PoE power by 15.4 W (802.3af), 30 W (802.3at), or 60 W (802.3bt). Generally, a 250 W power module supports eight interfaces of 15.4 W. A 500 W power module supports 24 interfaces of 15.4 W and 12 interfaces of 30 W. For details, see Tell You About PoE.

ACL configuration on S series switch
An ACL filters packets based on rules. A switch with an ACL configured matches packets based on the rules to obtain the packets of a certain type, and then decides to forward or discard these packets according to the policies used by the service module to which the ACL is applied. The S series switch supports basic ACL (2000-2999), advanced ACL (3000-3999), Layer 2 ACL (4000-4999), user-defined ACL (5000-5999), USER acl (6000-9999), basic ACL6 (2000-2999), and advanced ACL6 (3000-3999). For more information about the ACL feature supported by S series switches, except S1700, click S1720&S2700&S3700&S5700&S6700&S7700&S9700 Common Operation Guide or S1720&S2700&S3700&S5700&S6700&S7700&S9700 Typical Configuration Examples.

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