CCENT/CCNA ICND1 Official Exam Certification Guide - Chapter 3

Fundamentals of LANs Tiêu chuẩn lớp vật lý và liên kết dữ liệu làm việc với nhau để cho phép máy tính để gửi các bit với nhau trong một loại hình cụ thể của môi trường mạng vật lý. Hệ thống kết nối mở (OSI) vật lý lớp (Layer 1) xác định làm thế nào để gửi các bit trên một phương tiện kết nối mạng vật lý đặc biệt. Lớp liên kết dữ liệu (Layer 2) xác định một số quy tắc về các dữ liệu bạn đã được truyền đi, bao gồm cả địa chỉ xác...
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CCENT/CCNA ICND1 Official Exam Certification Guide - Chapter 3 1828xbook.fm Page 41 Thursday, July 26, 2007 3:10 PM 3 CHAPTER Fundamentals of LANs Physical and data link layer standards work together to allow computers to send bits to each other over a particular type of physical networking medium. The Open Systems Interconnection (OSI) physical layer (Layer 1) defines how to physically send bits over a particular physical networking medium. The data link layer (Layer 2) defines some rules about the data that is physically transmitted, including addresses that identify the sending device and the intended recipient, and rules about when a device can send (and when it should be silent), to name a few. This chapter explains some of the basics of local-area networks (LAN). The term LAN refers to a set of Layer 1 and 2 standards designed to work together for the purpose of implementing geographically small networks. This chapter introduces the concepts of LANs—in particular, Ethernet LANs. More-detailed coverage of LANs appears in Part II (Chapters 7 through 11). “Do I Know This Already?” Quiz The “Do I Know This Already?” quiz allows you to assess whether you should read the entire chapter. If you miss no more than one of these 11 self-assessment questions, you might want to move ahead to the “Exam Preparation Tasks” section. Table 3-1 lists the major headings in this chapter and the “Do I Know This Already?” quiz questions covering the material in those sections. This helps you assess your knowledge of these specific areas. The answers to the “Do I Know This Already?” quiz appear in Appendix A. “Do I Know This Already?” Foundation Topics Section-to-Question Mapping Table 3-1 Foundation Topics Section Questions An Overview of Modern Ethernet LANs 1 A Brief History of Ethernet 2 Ethernet UTP Cabling 3, 4 Improving Performance by Using Switches Instead of Hubs 5–7 Ethernet Data-Link Protocols 8–11 1828xbook.fm Page 42 Thursday, July 26, 2007 3:10 PM 42 Chapter 3: Fundamentals of LANs Which of the following is true about the cabling of a typical modern Ethernet LAN? 1. Connect each device in series using coaxial cabling a. Connect each device in series using UTP cabling b. Connect each device to a centralized LAN hub using UTP cabling c. Connect each device to a centralized LAN switch using UTP cabling d. Which of the following is true about the cabling of a 10BASE2 Ethernet LAN? 2. Connect each device in series using coaxial cabling a. Connect each device in series using UTP cabling b. Connect each device to a centralized LAN hub using UTP cabling c. Connect each device to a centralized LAN switch using UTP cabling d. Which of the following is true about Ethernet crossover cables? 3. Pins 1 and 2 are reversed on the other end of the cable. a. Pins 1 and 2 on one end of the cable connect to pins 3 and 6 on the other end of b. the cable. Pins 1 and 2 on one end of the cable connect to pins 3 and 4 on the other end of c. the cable. The cable can be up to 1000 meters long to cross over between buildings. d. None of the other answers is correct. e. Each answer lists two types of devices used in a 100BASE-TX network. If these 4. devices were connected with UTP Ethernet cables, which pairs of devices would require a straight-through cable? PC and router a. PC and switch b. Hub and switch c. Router and hub d. Wireless access point (Ethernet port) and switch e. 1828xbook.fm Page 43 Thursday, July 26, 2007 3:10 PM “Do I Know This Already ...