A communication system includes a plurality of high-performance communication devices located in a first communication network and having a first communication processing performance, and a low-performance communication device located in a second communication network and having a second communication processing performance. A high-performance communication device, which is one of the high-performance communication devices and is located at a boundary of connection with the low-performance communication device, restricts relay of a broadcast frame transmitted and received in the first communication network to the second communication network.