A Main Distribution Frame (MDF) is the central point in a building where external communication lines connect to the internal network. The MDF functions as the central hub where external telecommunications. An IDF (Intermediate Distribution Frame) is a distribution frame located in a central office or customer premises. Typically smaller than the MDF, the IDF provides a place where network switches and other devices. The MDF connects to your ISP and feeds high-speed fiber out to each IDF. That setup keeps latency low and speeds high. We usually run single-mode fiber from the MDF to each IDF.