Ethernet adaptive network repeater with auto-link-speed negotiation

An adaptive network repeater is disclosed for electronically connecting first and second subnetworks. The adaptive network repeater includes a first network interface coupled to the first subnetwork, a second network interface coupled to the second subnetwork, and a controller that monitors communication link status between the first and second subnetworks across the adaptive network repeater. Data received from the first subnetwork at the first network interface is retransmitted to the second subnetwork through the second network interface, and data received from the second subnetwork at the second network interface is retransmitted to the first subnetwork through the first network interface. When the controller determines that the first and second subnetworks want to communicate across the adaptive network repeater at incompatible communication speeds, the controller determines a compatible communication speed and causes the first and second subnetworks to communicate across the adaptive network repeater at the compatible communication speed.