Hi,

I just bought a CRS125-24G-1S-IN and want it to act like a router and a switch.
I´m a newbie but familiar with the "normal" RB´s, but how do I configure the CRS125-24G-1S-IN to work as a router-switch with firewall nat etc?

Hello, please, take a look at this CRS configuration example, it combines router-switch functionality for CRS1xx/2xx devices.
https://wiki.mikrotik.com/wiki/Manual:C ... AN_Routing