Congrats. So, the problem was in your LAN.
> It is a modem/router in one device.
It is common these days that consumer "routers" to be modem/router/wireless access point/file server/streaming server/... all in one!
> I disabled "bridge mode", which makes the device function only as a modem and not a router,
Isn't it the other way around? The device has to be either a bridge or a router. So if you _disable_ bridge, it'll become a router. (The modem functionality has to be there always, assuming the connection is xDSL.)
> and now my pi is connected to the internet and I can use the pi as a router.
My guess is that you have a block of public IP addresses. In that case ordinary routing (without NAT) is the right one.
It would be nice, if you could clarify these thing, for the benefit of the next visitor!
Installing and upgrading help
Moodlebox update and internet problem
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