How to find the cause of network failure in Debian 11?

Question

linux

All the best!
Guru give an answer, I've already broken my head. The essence of the problem is the following:
Debian 11 is on a netbook and works 24/7, it needs constant access via ssh. Periodically (there is no clear interval and criteria), the network disappears. It looks like this: there is no link from the router side, there is a link on the laptop, there is a ping of myself, I can access myself via ssh, there is no ping to the Internet and other members of the home network. Restarting NetworkManager does not save the situation, only reboot helps. Where to dig and where to look? How to get rid of this scourge?
UPD:
Now the network itself has somehow recovered and the laptop has become available over the network ... Everything is more wonderful and wonderful ...

Answer 1

So. The question can be considered closed: at the moment uptime
20:13:50 up 4 days, 22:29,
Solution of the issue: the beta firmware of the keenetic router was installed. The problem was purely hardware.

Answer 2

there is no link from the router side, there is a link on the laptop

Those. netbook connected by cable? Sounds like a hardware issue.
1. try to connect to another port of the router;
2. change the cable (although it is difficult to suspect it, but ...);
3. if 1 and 2 do not help, then conduct a simple experiment: take any serviceable switch (even a five-port one for 300 rubles), plug it between the router and the netbook and see which side the link is saved and which one is lost; if the link on the router disappears even with the intermediate switch, then the router is faulty; otherwise, the netbook's ethernet adapter may be faulty, then you can buy a USB-ethernet adapter.

Answer 3

is there a device on the network that can get the same ip address? like a statically configured ip? a typical example - another device receives this ip, pings now go there until the end of the address lifetime, then the router issues a new one (after all, the laptop has no network and it requests a new one) and again everything works until the next unfortunate set of circumstances

Answer 4

"It looks like this: there is no link from the router side" - dig the router logs. It looks like a hardware problem, try changing the cable, router port.