OliverStephenson
I’ll try to explain it.
Let’s say the Internet talkes english. The devices on a local lan talk german. In general a device on the LAN can’t directly talk to the a device on the Internet. You need a modem, this will translate to and from the internet for the devices on the LAN.
A normal router uses the same language on the wan side and on the lan side. But the Sunrise Internet Box talks english on the wan side (internet) and german on the lan side. it is a multi-function-device. So if you connect the Box to another router they don’t get along, because they don’t understand each other.
Also, the DSL Cable might look like a Network-Cable but they aren’t the same.