What is a collision domain and how does switching affect it?

• A. A collision domain is a broadcast domain.
• B. A collision domain is a VLAN that carries multiple broadcasts.
• C. A collision domain is the boundary where routing decisions are made.
• D. A collision domain is a network segment where collisions can occur; switches partition collision domains per port.

Answer: (D)

A collision domain is the network segment where multiple devices share the same medium and can cause data collisions if they transmit at the same time. In a traditional Ethernet setup with hubs, all devices on that shared segment belong to one collision domain, so collisions can involve any of them. A switch changes this by giving each port its own collision domain; devices connected to different ports don’t collide with each other because each port is its own separate segment. In practice, this reduces or eliminates collisions on a network path, especially when links are full-duplex. Remember that broadcast domains are a separate concept and VLANs control them; a switch by itself partitions collision domains per port but doesn’t inherently separate broadcast domains unless VLANs are used. Therefore, a collision domain is where collisions can occur, and switches partition collision domains per port.