How to detect and troubleshoot PoE failures？
In a basic PoE power supply system, the main components are the power supply equipment (PSE), the powered device (PD) and the PoE cable. When something goes wrong with PoE, most of the time, the error symptoms can simply manifest as the PoE switch not providing power and the powered device will stop working. There may be many factors causing the failure, including hardware device factors and software factors. How to accurately identify the source of PoE errors and minimize PoE troubleshooting time? This article details three common PoE failures and how to troubleshoot Power over Ethernet.
PoE Error 1: PoE switch does not provide power
PoE PD failure to start is one of the most common errors in PoE failure, usually caused by PoE component problems or incorrect configuration commands. Please follow these steps to resolve the issue:
Step 1: Check PoE IEEE standards and power supply modes of PSE and PD
If there are no quality issues with your PoE network switch and PD, you need to confirm whether both the PSE and PD comply with the PoE IEEE standard. Note that non-standard PoE switches, also known as passive PoE switches, always provide power over the Ethernet line at a specific voltage, regardless of whether the end device supports PoE or not. If not adequately prepared, passive PoE switches may burn out end devices. In addition, the power supply mode of PSE and PD is also a factor that may cause PoE failure. There are three PoE modes: Alternate A, Alternate B, and 4-pair transmission. If the PD only supports PoE mode B power supply and the PoE switch is based on Alternative A, the PD and PoE switch cannot work together. Please be sure to confirm the power supply mode of PSE and PD with the supplier.
Step 2: Check PoE cabling
Mismatched Ethernet cables and PoE ports can cause network failures. Additionally, PoE failures may occur if the cable has a hardware fault or does not meet the necessary standards. Therefore, it is highly recommended to ensure that the Ethernet cable supports PoE and is available before connecting a powered device.
Step 23: Check whether the PoE power supply is sufficient
The PSE device interface can automatically detect the PD when it is connected. If the power is insufficient, the PD will not be able to provide power. Ensure that the power used to run the PD does not exceed the power budget of the PoE network switch. If the PSE detects that the PD's power level is within its capacity, it will power the PD.
Step 4: Check PoE power management configuration
Check whether the switch interface is configured with automatic PoE power management configuration. If not, you will need to manually power the PD connected to the PoE network switch interface.
PoE Error 2: PoE PD intermittently loses power or reloads
What if a working PD stops powering or reloads intermittently? If there is a power outage during reinstallation or operation, it may be caused by insufficient power supply or poor quality of the PoE cable.
Step 1: Check if the PoE power supply is sufficient
When the PSE output power is insufficient to satisfy all PDs operating at full power consumption, the PoE PDs may intermittently power down or reload, causing the PoE switch to lose power. Take a network camera as an example. When testing all extended functions (such as pan, tilt, zoom, heater, wipers, etc.), the PD may consume more power during testing than required for normal operation. Without additional power, the camera may get stuck in a continuous boot cycle. To troubleshoot this PoE failure, measure how much power the network camera requires during boot and use the correct PSE to provide sufficient power.
Step 2: Check PoE cabling
If the Ethernet cable used in the PoE link is longer than 100 meters, or if there is a power outage due to the material and resistance of the cable itself, the PD will not receive enough power, causing problems such as network failure or latency. If the cable is not qualified, it will also cause PoE failure.
PoE Error 3: Some PDs are receiving power while other PDs on the same PSE are not
If a certain number of PDs can be powered on, but others are still powered off, you should check by following these tips:
Step 1: Check if other ports have available PDs
Check whether some PSE ports are faulty. Disconnect the PoE cable between the Ethernet switch port and the PD that cannot be powered. If the PD can still supply power normally after being connected to other PoE ports, it proves that some ports are faulty. Use the configure command to verify that the port is down or incorrectly disabled. If yes, please execute the command to enable the PoE function.
Step 2: Check PoE power
If a new PD is added to a PSE port and the PoE switch power budget is exhausted, the PD will not power on. Ensure that the remaining PoE power of the PSE is equal to or greater than the maximum output power required by the connected PD. Additionally, limit the current flow to each port to safe levels and use additional PSE devices when necessary.
PoE Error 4: PoE camera not receiving power
If your camera won't power on when using a PoE switch or PoE injector, you can follow the tips below to resolve the issue.
Step 1: Check if the camera is compatible with the PoE switch/PoE injector
Please check what type of PoE switch or PoE injector you can use with your camera. Make sure the PoE switch or PoE injector has the correct specifications.
Step 2: Check that the camera is fully connected to the PoE switch/PoE injector
Please check the PoE port lights on the PoE switch/PoE injector. If the light doesn't come on, you can plug the camera into a different port and try using another Ethernet cable. Make sure the switch's PoE ports are not rusty or damaged. This can be proven by replacing other good PoE ports.
Step 3: Check whether the camera PoE module is powered on
If the PoE module fails to provide power, please use a DC adapter with the correct output voltage to power the camera. Make sure the DC/AC adapter is available. Generally speaking, the adapter has an indicator light that can be used to determine whether power is being supplied. Some network cameras with DC/AC power interfaces can support DC12V/2A and AC 24V/3A power supply. Please ensure that the adapter specifications are consistent with the camera.
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