The difference between RJ45 network connector and RJ11 telephone connector

Different standards and sizes. Due to their different sizes (RJ11 connectors are 4 or 6 pins, RJ45 connectors are 8 pins), apparently RJ45 connector plugs cannot fit into RJ11 jacks. Instead, it‘s physically possible (RJ11 plugs are smaller than RJ45 jacks), giving the illusion that the two should or could work together. In fact, this is not the case. It is strongly recommended not to use RJ11 plugs for RJ45 connector sockets. Since RJ11 has no international standardization, its size, insertion force, insertion angle, etc. are not unified in accordance with the connector design requirements of international standards, so interoperability cannot be guaranteed. They even do damage to both. Since the RJ11 plug is smaller than the RJ45 connector socket, the plastic pieces on the sides of the plug can damage the metal pins that plug into the socket.