Intentionally Double-nat behind a Fritzbox


I have an OpenWRT (ASUS RT-AC51U) router wired to the (main) fritzbox router which is connected to the internet. Using Openwrt without any changes (except for removing the default wifi configs and sysupgrade to 21.02.2) makes it act like a switch and bridge the network from the main router.

But whenever I connect the openwrt router via lan to the main router, I can't access any of the settiongs via luci-web or ssh, only when I disconnect the lan from the main router and restart, any router settings can be done.

When only the openwrt-router is connected, the assigned ip-range my pc is in is 192.168.1.x but with the main router attached, it's 192.168.178.x.
Also the connection is slow when changing between attaching and detaching to the main router.

How do I intentionally create a own network within openwrt that doesn't interfere with the main router but still recieve an internet connection?

Do you want to create a network behind the OpenWrt router that is distinct from the upstream connection (i.e. the network created by the Fritzbox)?

If so, you will connect a cable between the fritzbox LAN into the Asus WAN port. If the Fritzbox is using the network, your OpenWrt default ( will work without any additional changes.

I first didn't connect the main router to the wan port, but now doing so and restarting it, made it work exactly as it want it to. Thanks!

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