Recently I've upgraded from a Buffalo WZR-HP-AG300H to a Fritz!Box 4040 and my download speed increased almost 50% on my 400Mbit cable connection, which is great. I've configured my new OpenWrt 18.06.4 setup mostly identical to the old one, but with the Fritz!Box 4040 I do experience a lot of instabilities. The OpenWrt router runs behind a cable router.
I've invested already a lot of time why the new router drops out my internet connection when just watching Youtube videos from LAN. To make it clear I do not experience this issue with WIFI, only on LAN.
So when watching videos e.g. on Youtube via LAN after some time (usually within minutes or less than an hour), my internet drops out completely. I cannot ping the OpenWrt router anymore on 192.168.1.1 or any other server on the internet like 18.104.22.168. From the internet to my OpenWrt router or to machines on my home network a ping is as well not possible anymore. A ping to my other machines on my home network continues to work fine. The only option at this point is to restart the OpenWrt router to get back internet connection (waiting some time or restarting the LAN/WAN interfaces is not enough).
I still can restart the OpenWRT router from WIFI via the LUCI web interface, somehow I can still access this via WIFI but not via LAN.
As I didn't find a similar issue when seaching this forum or on the internet I did order a new Fritz!Box 4040 to exclude hardware failure as a cause. But the new Fritz!Box 4040 shows the identical issue like the old one.
Reading the logs didn't tell me any hint what could be wrong my OpenWRT setup. As my old Buffalo router did run extremely stable for years, I can only assume it must be releated to the Fritz!Box OpenWrt image or to a special configuration.
Is somebody experience the same issues with OpenWrt?
Fritz!Box 4040 with OpenWrt 18.06.4 behind cable router (DS-lite)
eth1 - WAN+WAN6
eth0 - LAN
wlan0+wlan1 - bridge WIFI
wlan0 - guest WIFI
stubby for DNS over https
luci-ssl-openssl for https web interface
Firewall adjusted for my home network into 3 zones (LAN, WIFI, GUEST)
Some machines on my home network got a fixed IP assigned by OpenWrt