PoE Watchdog is a link-layer self-healing mechanism for powered devices (PDs) connected via PoE ports. Its core is to monitor the online status of the PD (such as traffic, link, and power supply) and automatically perform a power cycle when the device is unresponsive, avoiding manual on-site maintenance. It is suitable for unattended scenarios such as security cameras, industrial APs, and PLCs.

Core principles and triggering mechanisms

PoE Watchdog is based on a closed-loop process of "state detection + automatic reset", and is implemented as follows:

1. Detection Dimensions

Link status: Port physical layer UP/DOWN status (can be checked using display interface).

Traffic activity: If there is no traffic sent or received within a set time window (e.g., 30 seconds), it is judged as "no response".

PD power supply status: The PSE chip monitors the current/voltage of the PD in real time and triggers an alarm when there is an abnormality.

2. Trigger Action

Once the fault conditions are met, the switch performs a "power off → delay → power on" power cycle on the port. The default power off time is about 300-500ms (compliant with IEEE 802.3af/at standard). After restarting, PD detection and power supply negotiation are performed again.

3. Protection Mechanism

Supports "retry limit" (stops after 3 consecutive failed restarts to avoid infinite loop), and some high-end models support "intelligent delayed power-on" (avoids power overload caused by simultaneous restart of batch PDs).