Thank you for all the help
Can you set the modem into modem-only mode? So it won't connect itself?
That's the best way since you can use PPPoE on the Flint2 then.
This would be ideal, but I'm afraid my ISP might be a problem here (I will check that path though). The "modem/router" device is the sagemcom cs 50001
which is managed via their website. The only option I have there is to either use the device as its own WiFi router, or to switch to a bridge mode to one other specific device by providing that device's MAC address (Flint 2 mac address in this case).
If the VDSL PPPoE in the modem, the public IP changes only for the modem interface (pppoe-wan), the IP from Modem LAN -> Flint2 WAN is supposed to be a private IP.
This must be due to it being a modem/router device then, because the IP address that I see here in the Flint 2 settings is the public address of the modem (verified by going to any of the "what is my public IP address" websites):
The IP is also clearly different than the previous one (I have the previous one recorded)
May I know if the PC directly connect to the modem, the Ethernet adapter of PC works well?
It will take me a moment to test it with the cable (freshly moved the apartments and I am forced to use the WiFi for now), but to already provide a bit more info -> the "modem/router sagemcom device" can have its WiFi individually enabled via the ISP website while Flint 2 is working in bridge mode, and I think it can then work in parallel to the WiFi signal from Flint 2.
Please immediately export the syslogs if the WAN of the Flint disconnect to the Internet again, and PM me.
I will keep an eye on it. Given that it only happened after 10 days of running fine, it might take a while to get this to reproduce. But to give some context already, I woke up to the syslog spammed with messages like this one:
Fri Aug 9 10:12:27 2024 user.notice AdGuardHome[13123]: 2024/08/09 08:12:27.119275 [error] dnsproxy: upstream 8.8.8.8:53 failed to exchange ;shavar.services.mozilla.com. IN A in 64.761µs: dialing 8.8.8.8:53 over udp: dial udp 8.8.8.8:53: connect: network is unreachable
If you think it is useful, I could send the logs of what happened after I unplugged and plugged the cable connecting it to the modem and how it renegotiated the IP addresses afterwards.