Abstract: A multiport repeater for a data network operating on a CSMA or CSMA/CD protocol, for example an Ethernet local area network, has signals transmitted from port to port via a crosspoint switch or other appropriate switching means. The destination address of each incoming data frame is read and compared with a stored table to determine which port or ports the frame needs to be transmitted to, and the switching means is then operated to cease transmitting the frame unnecessarily to other ports. The remaining ports are thus returned to an idle state, and a second frame overlapping with the first can be received and retransmitted provided it does not require any of the ports that are in use in transmitting the first frame.