@woozle Thanks for the quick response! Unfortunately i am 300km away right now and i have remotely access only to the primary router. So i can't change the LAN network of the ISP modem. Also i have...

Well, my Archer A64 keep changing it's own LAN ip address constantly. Let me show you my settings: I have ISP modem(in bridge mode) --> my own primary router --> second router. The connection: From...