CCNA Exam: Collision Domains and Network Devices

Every Port in the Same Collision Domain

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On which type of device is every port in the same collision domain?



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A. B. C.


Collision domain A collision domain is, as the name implies, a part of a network where packet collisions can occur. A collision occurs when two devices send a packet at the same time on the shared network segment. The packets collide and both devices must send the packets again, which reduces network efficiency.

Collisions are often in a hub environment, because each port on a hub is in the same collision domain. By contrast, each port on a bridge, a switch or a router is in a separate collision domain.

Every port in the same collision domain means that if two devices transmit data at the same time on any of the ports, a collision will occur, and the data will be lost.

A hub is a Layer 1 device that forwards incoming frames out to all other ports, which means all devices connected to a hub are in the same collision domain. A hub does not have any intelligence to manage the traffic or isolate collisions, so it is not recommended to use a hub in a modern network.

On the other hand, both routers and Layer 2 switches create different collision domains for each port, which means that if a collision occurs on one port, it won't affect other ports.

Routers create different collision domains because they operate at Layer 3 of the OSI model and use logical addressing to forward packets between networks. When a packet arrives at a router, it checks the destination IP address and forwards it to the correct interface, which connects to a different network.

Layer 2 switches create different collision domains by using a technique called micro-segmentation, where each port is treated as a separate collision domain. When a switch receives a frame, it checks the destination MAC address and forwards it only to the port connected to that device. This reduces the likelihood of collisions and improves network performance.

Therefore, the correct answer is C. a hub, as every port is in the same collision domain, and any collision on one port will affect all other ports.