@Glassman1976 I can't replace the router, it used as a modem only. If I change my Network topology to - Router -> Deco -> Switch -> PC, should it work?

@Glassman1976 "Are all your devices behind the Deco?" - I think no, only Wireless devices. "Can you please give some details on your network topology?" -

@Glassman1976 My deco in router mode, and still, I get access to the local device in my network. what i do wrong?

I probably missed something. I enabled guest WIFI and connected it from my phone, then I run RDP to a local computer with the internal IP and success connect to it. To the best of my understanding,...