A collection of PCs, printers, and server are all connected to the same network segment and use the same subnet. All devices on this network segment must share the available bandwidth. If two or more hosts transmit the frames at the same times, the frames will collide and interferer.The boundary around such a shared network is called a collision domain.
Broadcast traffic sending by one host can reach all hosts on a network segment. All hosts deliver the broadcast traffic except Layer 3 devices. The extent of a Layer 2 network, where a broadcast frame can reach, is known as a broadcast domain.
Network Design Scence
To limit the size of a collision domain, we can connect smaller numbers of hosts to individual switch interfaces. To reduce the size of a broadcast domain, we can segment a network or break it up into smaller Layer 2 VLANs.