Which statement is true about collision domains on routers?

Which statement is true about collision domains on routers?

• A. All router ports share a single collision domain
• B. Each port on a router is a collision domain
• C. Routers have no collision domains
• D. Collision domains are defined only on hubs

Answer: (B)

Collision domains are sections of a network where only one device can transmit at a time without collisions. On a router, each interface connects to a different network segment, and the router isolates those segments from each other. Because traffic is routed between interfaces and not shared across them, each router port acts as its own collision domain. In other words, devices on one router link contend only with others on that same link, not with devices on other router interfaces. That’s why this statement is true: every port on a router represents a separate collision domain. By contrast, a hub does not segment collisions, so all devices on a hub share a single collision domain; a switch reduces collisions per port but does not create separate collision domains across interfaces without VLANs; routers inherently place a boundary that creates a new collision domain for each interface. The idea that routers have no collision domains is incorrect, and collision domains aren’t defined only on hubs.

Collision domains are sections of a network where only one device can transmit at a time without collisions. On a router, each interface connects to a different network segment, and the router isolates those segments from each other. Because traffic is routed between interfaces and not shared across them, each router port acts as its own collision domain. In other words, devices on one router link contend only with others on that same link, not with devices on other router interfaces.

That’s why this statement is true: every port on a router represents a separate collision domain. By contrast, a hub does not segment collisions, so all devices on a hub share a single collision domain; a switch reduces collisions per port but does not create separate collision domains across interfaces without VLANs; routers inherently place a boundary that creates a new collision domain for each interface. The idea that routers have no collision domains is incorrect, and collision domains aren’t defined only on hubs.