@Kevin_Z Hi Kevin, thanks for the replied, i think i know where the problem, which my ISP router act as a DHCP, that why my main deco can't provide proper DHCP function. just to double confirm, i...

i got 6 units of Deco M9 Plus, some of them is in really far range, but there is a cat6 cable connected to the switch (the main unit is connected to the switch as well) posible that sub units plug in...