rainer:

Recently I've upgraded from a Buffalo WZR-HP-AG300H to a Fritz!Box 4040. My download speed doubled on my 400Mbit cable connection but since then I do experience as well a lot of instabilities where my previous setup was 100% stable. The OpenWrt router runs behind a DS-lite cable router (Fritz!Box 6591).

Just by watching a YouTube video (e.g. music) or by downloading with wget some files (e.g. Linux Iso images) via the LAN interface, OpenWrt on the Fritz!Box 4040 will randomly drop the internet connection completely. It disconnects the router, no ping with IPv4 or IPv6 is possible then anymore from my machine. Strangely I can access the web interface only via Wifi to reboot the router. The lost connection doesn't come back after some time, the router requires a reboot.

If I avoid YouTube/wget, the OpenWrt router runs quite well when just doing normal internet browsing and running a web server behind the OpenWrt router.

In the log files I do not see any special hint what might cause the drop outs. I've tested multiple different setups already, ordered a second Fritz!Box 4040 to exclude a hardware issue, tested with 2 different cable routers, did a factory reset, flashed the latest OpenWrt snapshot (plus added luci) and used the standard configs, nothing seems to help. I assume that it is related somehow to IPv6. There are other users with the Fritz!Box 4040 that do not experience these issues, but they use it only with IPv4. As I have DS-lite, I need to use IPv6 to avoid the 6to4 tunneling on the cable router.

• Fritz!Box 4040
• OpenWrt 18.06.4 + Dev Snapshot 2019-11-10
• IPv4 and IPv6 incl. Prefix delegation to LAN interface
• Watch YouTube videos or download files with wget

For reference, I did a post on the forum: https://forum.openwrt.org/t/fritz-box-4040-drops-out-internet-connection-if-watching-youtube-from-lan/46753