What Is a Collision Domain?
a Collision Domain — a network segment where devices share bandwidth and their transmissions can collide — eliminated on modern full-duplex switch ports, one per port.
How it works
On old shared media (hubs), devices contended for the wire and transmissions could collide, requiring CSMA/CD to detect and recover. Each switch port is its own collision domain, and full-duplex links eliminate collisions entirely. So a hub is one big collision domain; a switch gives every port its own, collision-free.
Why it matters
The collision domain concept explains why switches replaced hubs and why modern switched networks have no collisions. Distinguishing it from a broadcast domain (switches split collision domains but not broadcast domains) is a classic exam and interview point.
Frequently asked questions
What is a collision domain?
A network segment where devices share bandwidth and transmissions can collide — each switch port is its own collision domain, and full-duplex eliminates collisions.
How many collision domains does a switch have?
One per port — unlike a hub, which puts all ports in a single shared collision domain.
What is the difference between a collision and broadcast domain?
Switches separate collision domains (per port) but not broadcast domains; routers and VLANs separate broadcast domains.
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