How I Built a Tiny WAN Failover Tool for My 8‑MB OpenWrt Router (and Why mwan3 Wasn’t an Option)
1. The Problem: When the Internet Goes Down, So Does My Home Network
Like many of us, I rely on a wired broadband connection for my home internet. But things happen—the provider goes offline for maintenance, a cable gets cut, or (let’s be honest) you forget to pay the bill. When that happens, I wanted my router to automatically switch to a backup connection: a Wi‑Fi hotspot from my phone.
I’m running OpenWrt on a tiny Xiaomi Mi Router C4 . It’s a cheap, reliable device, but it comes with severe storage constraints. Here’s what the filesystem looks like:
Filesystem 1K-blocks Used Available Use% Mounted on
