Oh well, I spent a good hour trying to push the cat cable behind the wall, luckily I could sometimes see the cable through cracks where the wall meets the floor (it's not finished yet
) and eventually got it squeezed through a very small opening at the end (aah, all the jokes that could be made here...) So I got my cable to the core!
For the record, I didn't want to connect the core wirelessly to all the other devices, just to the router. Then I wanted to connect the core, through a switch, with the MDs... But that far-fetched idea won't be necessary, thank god!