ISP CGNAT broke my home lab
In the world of the homelab community, there is an unspoken mandate: when things go wrong, you always check your own setup first. It’s the foundational rule of troubleshooting, a habit born from countless hours spent wrestling with servers and networks.
A few days ago, I experienced this philosophy firsthand. One morning, my external access vanished. The digital doors to my private network were suddenly locked. Instinctively, I began the familiar ritual of deep-dive diagnostics. I meticulously examined every layer: the internet connection itself, the router settings, the firewall configurations, and the reverse proxy setup.
Every component was perfect. The server running behind the firewall was humming along happily; the services were operational; and the internet, for the rest of the world, was functioning flawlessly. Yet, external access remained stubbornly dead. Everything appeared to be configured exactly as it should be, leaving me in a state of pure, digital frustration.
After exhausting all internal possibilities, I shifted tactics. I stopped looking at what I controlled and started looking at what didn’t. I began rechecking the boundaries of my setup, focusing on the subtle interactions happening between my local network and the vast expanse of the wider internet.
And that is when the puzzle clicked into place. The fault was not within my carefully constructed domain. Something had quietly shifted—an unseen variable between my router and the global network—a change that went unnoticed by me while I was focused entirely on the internal architecture.
It was a powerful reminder that sometimes, the most elusive bugs aren’t found in the code or the configuration you wrote, but in the complex ecosystem of the outside world. The real lesson? Sometimes the solution lies just beyond the perimeter of your own setup.
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