Bind IP to MAC address

I having trouble trying to bind my TP switches, Xiaomi lights to Hass.io. Many times TP Switches or Xiaomi lights are unavailable.

My modem/router is Asus AC68 and the clients displaying showing different mac address to what I am expecting - so it may be a router problem rather than anything to do with hass.io. Wondered if anyone else had this similar problem.