Ethernet is a shared transmission medium network, so network nodes transmit using the same medium. In simple Ethernet networks, every node detects all network traffic. Creating separate collision domains reduces the number of devices that receive any frame, increasing overall network performance.

A switch examines the destination MAC address for each frame and forwards the frame to the destination segment. A node may send a broadcast message to see what other nodes respond as a way of discovering network resources. Ethernet uses a MAC broadcast address to handle broadcast transmissions. Switches that receive a frame with a MAC broadcast address send the frame to all network segments. All nodes that receive broadcast frames in a network belong to the same broadcast domain.