@Henkan Well, you gave network layout that does not mention second switch. You ask what could be the problem when connecting Satellite Deco to that second switch. You need to provide more details. To...

@Blufkip It is possible Ethernet link between switch 2 and switch 1 is broken. You should check Ethernet cable and connectivity between these two switches. The following forum topic discusses similar...

@Ajmal_T I would recommend unmanaged switch. TP-Link recommends TL-SG108 for 8-port unmanaged switch. I like your choice better, because TL-SG108E has LED lights that show link speed - very useful...

@NikSf153 You will not need to add a Deco. This is how you new network layout will look, with Deco mesh running in Access Point mode: If you have enough Ethernet ports on new router you are going to...

@NikSf153 Depends, what is your ONU: device with just one Ethernet port, or is it Gateway (modem/router) type of device? If it is Gateway, you can switch Deco mesh to Access Point mode, but if it is...

@NikSf153 You will need to connect them like it is on first or second diagram, with Main Deco connecting directly to ONU and switch or Satellite Deco - to second port of Main Deco.