TP-LINK Archer C7 limits connectivity on devices picked (seemingly) randomly

Question

TP-Link Archer C7 v5 updated to last possible version of firmware.

Today, as I was connected to it's network, my laptop (Manjaro Linux Machine) displayed a "Limited Connectivity" notification. All other devices, connected in the same network didn't have any problem. I still was able to access my router's control panel from a web browser and restarted the device. A few hours later, one of my friends in the same room, saw the same notification on his laptop (Windows 10 machine). I again restarted the router. Half an hour later my phone (Android) displayed a notification "This network is not connected to the Internet" (or something similar).

Everytime, to restart the device, I open it's web-based control panel and there is nothing unusual there: Access Control is off, Traffic Statistics are on and they count the bytes normally (even of the limited devices, because they generate some LAN-based traffic), System Log shows nothing suspicious (last record in System Log is always from the last reboot, and it shows what services are started or stopped).

What could be problematic and where to look for potential solution?

Edit (Answering Albin's comment):

what happens if you do a ping and a traceroute on the affected client (on google.com and 8.8.8.8)?

If I ping 8.8.8.8 or whatever IP address FROM the affected device, I get a "Destination host is unreachable" response. Same for tracert.

what happens if you ping the router via IP FROM an effected device?

Absolutely no problem the ping returns with a time less than one millisecond

what happens if you ping 8.8.8.8 FROM THE ROUTER while at least one device is effected?

Again, everything is as it's supposed to be. The ping returns correctly with a time of 6 to 7 milliseconds.

Does it also happen if you disconnect all but one device?

Yes

What's the devices/routers IP and MAC address and how are they connected?

Device's IP is 192.168.0.100 given by the router's DHCP server (and reserved by MAC).

Router's IP is 192.168.0.1, the default class C IP

Both MAC addresses are different and the router doesn't use any LAN device's MAC.

If it doesn't happen with only one client, how many devices are there and how are the devices connected (Layer1,2,3)?

There are 3 to 5 devices constantly connected to the network (never less than 3) connected via Ethernet cable and wifi (both 2,4 GHz and 5GHz). This problem, however, I notice, only exists for the outgoing traffic. One of the devices inside the network is a Linux server with an SSH running on it, and there is no problem if I want to connect to it from the outside world, while the server is affected by this problem (the needed ports are forwarded).

The ISP doesn't see any problems on their side.

Answer 1

To summarize your problem:

Everything is working fine after restarting the router. After 30min up to a few hours, suddenly one of the clients is not able to connect to an internet IP anymore (e.g. 8.8.8.8 - ping shows "Destination host is unreachable" response), while other clients including the router still have access to the internet. The affected client still has access to the router though. After restarting the router everything goes back to normal. This also happens if only one device is connected to the router.

Assuming my summary is correct we can conclude that the fault most likely lies with the router which is responsible for "forwarding the packets to the internet". Since there doesn't seem to be any diagnostic on the router to check if the packets from the client arrive and what the router is doing with them (apparently they are not routed) we can not diagnose the problem much further. Since we pretty much narrowed the problem down to the router, at this point I would suggest contacting the TP-Link support since they have enough information to go on.

An additional test would be to test this configuration with a different router (e.g. a software router) and use the TP-Link router just as a switch/AP. If the routing on the TP-Link was responsible for the problem, it should be gone with the software router.

Note: I have a few more questions - see my comments to your question.

Answer 2

Try this : Advanced > Security > Settings > DoS Protection > Disable