@David-TP 

Hi David,

thanks for your reply!

The system is as indicated below, both deco's are connected to the (main) network switch, type TP-LINK: SG1008D

ISP modem--- <cable> -- (main) network switch --<cable>- main Deco X60---<cable>---network switch---- some other wired devices

                                                                   \--<cable>  satellite Deco X60#1 ---<cable>---network switch---- some other wired devices

                                                                                      \----<Wi-Fi>---satellite satellite Deco X60#2

ISP modem is situated at the front door, from there I arranged wired connections to multiple rooms in my house.

Main Deco is on 1st floor,  #1 in living room (ground level), #2 on 2nd floor (wireless).

I placed the main deco on purpose on the 1st floor (my office for maintenance purposes and other 2 devices are within wifi range.

All leds remain green and I stll have a connection when located on the 1st or second floor. I even swapped the units, but again the one that was connected via wire (living room) stopped working after a while. So it seems to be related to a wired setup. I would really like to use them wired, the speed is much higher then!

I have not tried to connect them directly (in series as you suggest).

Best regards, 

Pieter