An Ethernet Physical layer (PHY) device includes a PHY interface and PHY circuitry. The PHY interface is configured to connect to a physical link. The PHY circuitry is configured to generate layer-1 frames that carry data for transmission to a peer Ethernet PHY device, to insert among the layer-1 frames one or more management frames that are separate from the layer-1 frames and that are configured to control a General-Purpose Input-Output (GPIO) port associated with the peer Ethernet PHY device, to transmit the layer-1 frames and the inserted management frames, via the PHY interface, to the peer Ethernet PHY device over the physical link, for controlling one or more operations of the GPIO port associated with the peer Ethernet PHY device, and to receive, via the PHY interface, one or more verifications acknowledging that the one or more management frames were received successfully at the peer Ethernet PHY device.