12V Ethernet Heartbeat PCB

I need a compact-footprint PCB that runs on a solid 12 V input and plugs straight into Ethernet so it can sit inside my equipment rack and let the rest of my system know everything is still alive. The board’s sole job is to send a small heartbeat packet at set intervals and, if the link ever drops, push an immediate network-status alert that my database can log. Remote-monitoring bells and whistles are not required right now; reliable data transmission and clear link reporting are the priorities.

You can choose the silicon you are most comfortable with—an MCU with an integrated MAC/PHY, an external PHY hanging off an ESP32, or another combination—so long as it boots quickly, keeps the BOM lean, and exposes a straightforward way for me to adjust the heartbeat interval later (UART, SWD, or similar).

What I will need from you:
• Schematic and compact four-layer (or tighter) PCB layout ready for fast fabrication, including all source files and Gerbers
• A concise BOM with current component availability noted
• Firmware that boots, acquires a DHCP lease (or falls back to static), and transmits the heartbeat plus a link-up/link-down status message I can parse on my server
• Brief bring-up instructions so I can reproduce your test results on my end

If you can drop test points for future power and signal probing and pay attention to good 12 V input decoupling, even better. Let’s keep the design tight, reliable, and ready for production once the prototype checks out.

I need the ability to be able to program it using c++ to setup all network and web server details