Module 8: Ethernet Switching Overview

Ethernet Switching Overview
Shared Ethernet works extremely well under ideal conditions. If the number of devices that try to access the network is low, the number of collisions stays well within acceptable limits. However, when the number of users on the network increases, the number of collisions can significantly reduce performance. Bridges were developed to help correct performance problems that arose from increased collisions. Switches evolved from bridges to become the main technology in modern Ethernet LANs.


Collisions and broadcasts are expected events in modern networks. They are engineered into the design of Ethernet and higher layer technologies. However, when collisions and broadcasts occur in numbers that are above the optimum, network performance suffers. Collision domains and broadcast domains should be designed to limit the negative effects of collisions and broadcasts. This module explores the effects of collisions and broadcasts on network traffic and then describes how bridges and routers are used to segment networks for improved performance.

This module covers some of the objectives for the CCNA 640-801, INTRO 640-821, and ICND 640-811 exams.

Students who complete this module should be able to perform the following tasks:

• Define bridging and switching
• Define and describe the content-addressable memory (CAM) table
• Define latency
• Describe store-and-forward and cut-through packet switching modes
• Explain Spanning-Tree Protocol (STP)
• Define collisions, broadcasts, collision domains, and broadcast domains
• Identify the Layers 1, 2, and 3 devices used to create collision domains and broadcast domains
• Discuss data flow and problems with broadcasts
• Explain network segmentation and list the devices used to create segments