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Module 4: Switching Concepts / Overview

Module 4: Switching Concepts
Overview

LAN design has evolved. Network designers until very recently used hubs and bridges to build networks. Now switches and routers are the key components in LAN design, and the capabilities and performance of these devices continue to improve.
This module describes the roots of modern Ethernet LANs with an emphasis on the evolution of Ethernet/802.3, the most commonly deployed LAN architecture. A look at the historical context of LAN development and various network devices that can be utilized at different layers of the OSI model will help students better understand the reasons why network devices have evolved as they have.
Until recently, repeaters were used in most Ethernet networks. Network performance suffered as too many devices shared the same segment. Network engineers then added bridges to create multiple collision domains. As networks grew in size and complexity, the bridge evolved into the modern switch which allows microsegmentation of the network. Modern networks are now built with switches and routers, often with both functionalities in one device.
Many modern switches are capable of performing varied and complex tasks in the network. This module will provide an introduction to network segmentation and will describe the basics of switch operation.
Switches and bridges perform much of the heavy work in LANs where they make nearly instantaneous decisions when frames are received. This module describes in detail how switches learn the physical addresses of nodes, and how switches transmit and filter frames. This module also describes the principles of LAN segmentation and collision domains.
Switches are Layer 2 devices that are used to increase available bandwidth and reduce network congestion. A switch can segment a LAN into micro segments, which are segments with only a single host. Micro segmentation creates multiple collision-free domains from one large domain. As a Layer 2 device, the LAN switch increases the number of collision domains, but all hosts connected to the switch are still part of the same broadcast domain.
This module covers some of the objectives for the CCNA 640-801 and ICND 640-811 exams.  
Students who complete this module should be able to perform the following tasks:
  • Describe the history and function of shared, or half-duplex Ethernet
  • Define collision as it relates to Ethernet networks
  • Define CSMA/CD
  • Describe some of the key elements that affect network performance
  • Describe the function of repeaters
  • Define network latency
  • Define transmission time
  • Define network segmentation with routers, switches, and bridges
  • Define Ethernet switch latency
  • Explain the differences between Layer 2 and Layer 3 switching
  • Define symmetric and asymmetric switching
  • Define memory buffering
  • Compare and contrast store-and-forward and cut-through switching
  • Understand the differences between hubs, bridges, and switches
  • Describe the main functions of switches
  • List the major switch frame transmission modes
  • Describe the process by which switches learn addresses
  • Identify and define forwarding modes
  • Define LAN segmentation
  • Define micro segmentation with the use of switches
  • Describe the frame-filtering process
  • Compare and contrast collision and broadcast domains
  • Identify the cables needed to connect switches to workstations
Identify the cables needed to connect switches to other switches 

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