Tasmota device gone after DHCP server failure

[belveder79]

I'm running around 50 Tasmota devices around my home, and I have to say that I usually do not encounter any major issues. My basic setup is running a Mesh Wifi with an additional NanoPi R5C as a DHCP server, VPN server and so on. The DHCP server has a lot of static IPs assigned to the individual devices with a default 4 hour lease time.

Just recently the DHCP server went down accidentally for more than 4 hours when I was not at home. Returning from work, I started it again, but quite a dozen of Tasmota devices did never come back to the WiFi network; say, they never requested or received their static IP from the DHCP server. I can't say for sure, but I suspect that it was primarily those devices for which the lease ran out shortly after the DHCP server went down (and that therefore were trying to query a DHCP lease for hours).

Ok, for all the devices I was able to access easily and that did not come back, I just unplugged them and they came back immediately. This means that unpowering them is likely the standard go-to solution. However, for all the devices that I can access only with some effort (inside walls, etc.) I would also need to unpower them, and I bet they come back also, but I did not do that yet. This would mean I need to "unpower parts or even the whole house" as a rather drastic measure to get 2 or 3 Tasmota switches back into the game. Btw, the are NOT in AP mode, because this is what I checked first.

There are a ton of fallbacks and fixes in Tasmota, like querying alternative APs, switching WIFIs, rebooting etc., but how about the situation where

• the WIFI is there and can be accessed, but
• there is no DHCP IP assigned for hours

It's difficult debug, because I can't access the faulty devices, and if I cut power, they go back to normal.

Therefore: does anyone have an idea what happens to a Tasmota driven device in case WLAN is ok, but DHCP is not, for hours? Is this potentially a reproducible issue that deserves a fix?