@terziyski Thanks, sadly it did not help. I upgraded to the beta FW and I disabled OneMesh. For the whole day it seemed that this might have helped... but in the evening came the first 15-second dropout.

Before that I had a cheap 100 Mbps router that worked flawlessly. Then my provider increased the internet speed to 300 Mbps so I had to upgrade the router to a 1 Gbps model and this C6 was among the most popular choices in our biggest online store... I could buy a new one (same model) or upgrade to TPLink AX10 to see if it helps but I have a feeling this might be a FW issue and the replacement will have the same problems...

@terziyski Yes, I will stick to the C6 v2 at the moment and we'll see what the next stable firmware version brings.

I do have WiFi all over my house but that is managed by several Uniquiti Unifi PoE devices because they look really cool on the walls :-) So my main TPLink router has the WiFi switched completely off. It's just the router between the outside world (optical fiber from the neighbours is converted to an ethernet cable that leads to this router) and my inner network that consists of two 24p gigabit switches and tons of ethernet cables as my house is on Loxone (smart home? Not sure what it's called in English). You know, cameras, sensors, NAS servers, smart fridge, everything :-D But it's been like this for several years and has always worked fine. Just when the internet speed increased I upgraded the router. And the router config isn't complicated, basically just a lot of IP addresses are reserved/fixed and there may be some port forwarding and that's about it I think. It's just that it took me the whole day to describe everything properly, to find out which IP/MAC belongs to which device in the house, some IPs are fixed, some are dynamically assigned.

Anyway, TPLink has - IMO - an easy configuration interface (although it used to be much simplier in the old TPLinks that I had 5-10 years ago). So I'd like to stick to this brand and I can live with these short dropouts... but they are annoying anyway. (At first I thought they were internet dropouts but then I noticed that the whole intranet goes off).

I don't see anything in the system log, just some standard DHCP server communication and that even seems to be done at a different time than the dropout.

@terziyski Unfortunately I never manage to get to the router quickly enough to look at the LED lights. The router is located in a different part of my house than where my computer is and the dropouts are absolutely random and short (10-15 seconds) so by the time I get to my "NAS / server room" the intranet is back online.

I bought a new Archer C6 and replaced the old one but it did not help. So my last option is to replace the ethernet cables (that were working fine before I bought this router) and also the power cable and if even that fails I will simply buy an ASUS router instead :-)

The weird thing is that the router dropout "disables" my local network too. As I said, my topology basically is: optical cable from the street => Archer C6 => 24port switch => individual ethernet sockets in the rooms. So when the router's configuration is wrong (when installing a new one or something), I may not be able to connect to the internet, of course, but intranet still works (for example accessing my NAS or cameras on the house). Isn't it weird that these random short router dropouts disable the whole intranet? Shouldn't I still be able to access the network drives via the 24port switch? (I wouldn't blame the router but the dropouts started appearing exactly on the day when I replaced my old 100Mbps router by this new gigabit Archer C6).

After months of testing I'd say that most dropouts occur when I download or (even more often) upload a large file (hundreds of megabytes or a couple of gigabytes). So I did some more googling and found out that some people reported the very same issue for other types of TP-Link routers (even DSL). Somebody suggested to enable QoS in the advanced settings so I did that. I set the upload/download speed roughly equal to my maximum speed (500 Mbps download, 300 Mbps upload) - the figures are not important I think.

Earlier today my intranet (not internet) connection dropped five times during 15 minutes while I was trying to upload about 10 GB of FLAC files which was really driving my crazy. After I enabled QoS there hasn't been any dropout yet. Perhaps this is really the solution? I'm writing it here to help others who may face the same issue. Enabling QoS MIGHT be the solution. Or maybe not - but in my case it improved the connection stability for sure.