Similarly, I use an ESP8266 to supervise my wifi router and cable modem. Any trouble, reboot!
For the router, it just tries to connect to the appropriate SSID, and then tries to ping the router, and if either of those fails, it swaps to the other router. I have two identical routers with identical configs, with their power connected to the NO and NC contacts of an SPDT relay. If one fails, it just toggles the relay state to switch to the other.
If the router is up, the watchdog tries to load the cable modem's status page, and tries to ping any of three different IPs I've identified within my ISP's network which seem to be either the CMTS or closely associated hardware, and should indicate aliveness of the HFC plant -- I don't want to bother rebooting if the failure isn't something that a reboot could solve. Sadly I haven't figured out how to have two cable modems with the same MAC such that I could swap between them too, and the ISP won't let me have two modems on the same account, so my only resort if the CM fails is to reboot it and hope for the best.
This, plus a rack of batteries that'll keep the router and modem running for 30-plus hours in a utility outage, has kept me online nearly-continuously since May of 2020 when I built it. The code is an absolute horror-show (I'm much better with a soldering iron than an arduino), but in practice it's been rock solid.
For the router, it just tries to connect to the appropriate SSID, and then tries to ping the router, and if either of those fails, it swaps to the other router. I have two identical routers with identical configs, with their power connected to the NO and NC contacts of an SPDT relay. If one fails, it just toggles the relay state to switch to the other.
If the router is up, the watchdog tries to load the cable modem's status page, and tries to ping any of three different IPs I've identified within my ISP's network which seem to be either the CMTS or closely associated hardware, and should indicate aliveness of the HFC plant -- I don't want to bother rebooting if the failure isn't something that a reboot could solve. Sadly I haven't figured out how to have two cable modems with the same MAC such that I could swap between them too, and the ISP won't let me have two modems on the same account, so my only resort if the CM fails is to reboot it and hope for the best.
This, plus a rack of batteries that'll keep the router and modem running for 30-plus hours in a utility outage, has kept me online nearly-continuously since May of 2020 when I built it. The code is an absolute horror-show (I'm much better with a soldering iron than an arduino), but in practice it's been rock solid.