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CCNA Exam Prep: Data Link Networking Concepts

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This chapter will help you prepare for the CCNA exam, with a focus on data link networking. Sample questions with detailed answers are included to help you review for the exam.
This chapter is from the book

This chapter is from the book


This chapter covers the following Cisco-specified objectives for the "Technology" section of the CCNA exam:

Compare and contrast key characteristics of LAN environments

Describe network communications using layered models

Describe the components of network devices

This chapter also covers the following Cisco-specified objective for the "Planning and Designing" section of the CCNA exam:

Design a simple LAN using Cisco technology

  • A network device may utilize various components to achieve connectivity and increase functionality. These components are fundamental to internetworking.
  • This chapter specifically focuses on the Data Link layer of the OSI model and how network communications occur at this layer.
  • LAN environments at the Data Link layer may be set up with token ring, Fiber Distributed Data Interface (FDDI), or one of many ethernet data-link protocols.
  • Various network designs or layouts commonly are used to set up a LAN. At the Data Link layer, LANs may be connected with either a bridge or a switch. The operation of these devices is described in Chapter 8, "Bridging and Switching Operations."


  • Introduction
  • Data Link Protocols
    • Token Ring
    • FDDI
    • Ethernet at the Data Link Layer
      • Ethernet Addressing
      • Ethernet Framing
  • Physical Ethernet Standards
    • Ethernet
    • Fast Ethernet
    • Gigabit Ethernet
    • 10-Gigabit Ethernet (10GbE)
    • Long Reach Ethernet
  • Data Link Layer Devices
    • Bridges
    • Switches
  • Duplex
  • Microsegmentation
  • Chapter Summary
  • Apply Your Knowledge

Study Strategies

  • Read the objectives at the beginning of the chapter.
  • Familiarize yourself with token ring and FDDI protocols.
  • Define the IEEE MAC unicast, broadcast, and multicast addresses.
  • Review the ethernet family of protocols and be able to identify the characteristics of each protocol.
  • Name the devices that are used at the Data Link layer and important traits of each device.
  • Define duplex.
  • Describe microsegmentation.


Several data link networking concepts were first introduced in the discussion of the Data Link layer or Layer 2 of the OSI model in Chapter 1, "Standard Internetworking Models." Again, it is important to understand the layered architecture of the OSI model to grasp the fundamentals of how a network operates. Although Chapter 2, "Physical Layer Networking Concepts," went over concepts that define the Physical layer of the OSI model, this chapter goes over concepts that define how a network operates at the Data Link layer specifically.

Important Data Link LAN topics to understand for the CCNA exam include the protocols, addressing, and devices that are used at Layer 2. Cisco specified several objectives related to LAN technologies, which are prevalent at Layer 1 and Layer 2. Let’s begin with three Data Link layer protocols: token ring, FDDI, and ethernet.

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