Tipos de sensores - Sensores utilizados en lenguas electrónicas

CAPÍTULO 2: FUNDAMENTO TEÓRICO

2.3. Sensores utilizados en lenguas electrónicas

2.3.2. Tipos de sensores

Cisco folklore tells of the day in 1998 when Cisco’s revenues from LAN switching and hub products exceeded router revenues. That event in Cisco’s history was significant because most people in the marketplace thought of Cisco as “that router company” for a long time. In fact, Cisco would prefer to even shake the reputation as a great router/switch/hub company and instead be known for empowering the Internet generation, a catch-phrase from the company’s television ads.

So, if switches and hubs drive more revenue for Cisco, why is most of the popular Cisco certification about routers and routing issues? One issue is that LAN (Layer 2) issues are inherently less complicated than Layer 3 issues. However, that in no way means that LAN issues are not complicated; there are simply fewer concepts and issues to consider. Furthermore, because Layer 3-aware devices, such as routers, make extensive use of Layer 2 features to forward packets, the routing-centric topics can never totally ignore LAN and WAN Layer 2 concepts. So, this book includes one LAN-specific chapter and one WAN- specific chapter (Chapter 8, “WAN Protocols and Design”), in addition to the more lengthy coverage of routing.

This single chapter devoted totally to LANs reviews LAN basics, with a concentration on Ethernet. This chapter explains bridging and switching, along with some comparisons of bridging, switching, and routing. This chapter also covers Spanning Tree to a depth beyond what is probably needed for the exam, but understanding Spanning Tree is very important to the typical jobs performed by CCNAs. This chapter also covers virtual local-area networks (VLANs) and offers some switch configuration examples.

Cisco expects CCNAs to remember the names and functions of the LAN standards, not just the concepts behind them. So, while the concepts in this chapter might in part be review and in part be new information or a reminder of something you have forgotten, do not neglect to memorize the LAN standard’s names, at least. The concepts are very important to your success in your job; knowing the names of standards is very important to being able to communicate about your networks, which is one of Cisco’s expectations for CCNAs.

How to Best Use This Chapter

By taking the following steps, you can make better use of your study time:

•

Keep your notes and the answers for all your work with this book in one place, for easy reference.

130 Chapter 4: Bridges/Switches and LAN Design

•

Take the “Do I Know This Already?” quiz, and write down your answers. Studies show

that retention is significantly increased through writing down facts and concepts, even if you never look at the information again.

•

Use the diagram in Figure 4-1 to guide you to the next step.

Figure 4-1 How to Use This Chapter

“Do I Know This Already?” Quiz

The purpose of the “Do I Know This Already?” quiz is to help you decide what parts of this chapter to use. If you already intend to read the entire chapter, you do not necessarily need to answer these questions now.

This 16-question quiz helps you determine how to spend your limited study time. The quiz is sectioned into four smaller four-question “quizlets,” which correspond to the three major headings in the chapter. Suggestions on how to spend your time in this chapter, based on your quiz scores, are outlined in Figure 4-1. Use Table 4-1 to record your score.

Table 4-1 Scoresheet for Quiz and Quizlets

Quizlet Number

Foundation Topics Section Covering

These Questions Questions Score

1 LAN Overview 1 to 4

2 Bridging, Switching, and Spanning Tree 5 to 8

3 Virtual LANs 9 to 12

"Do I Know This Already?" Quiz

Read Foundation Topics Read Foundation Summary Read Related Foundation Topics Subsection Q&A Scenarios Go to Next Chapter Low Score Low Quizlet Score Medium Score High Score, Want More Review High Score

“Do I Know This Already?” Quiz 131

1 What do the letters MAC stand for? What other terms have you heard to describe the same or similar concept?

___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________

2 What standards body owns the process of ensuring unique MAC addresses worldwide?

3 What is the distance limitation of 10BaseT? 100BaseTX?

4 How fast is Fast Ethernet?

5 What routing protocol does a transparent bridge use to learn about Layer 3 addressing groupings?

4 LAN Switch Configuration 13 to 16

All questions 1 to 16

Table 4-1 Scoresheet for Quiz and Quizlets (Continued)

Quizlet Number

Foundation Topics Section Covering

These Questions Questions Score

132 Chapter 4: Bridges/Switches and LAN Design

6 Name two of the methods of internal switching on typical switches today. Which provides less latency for an individual frame?

__________________________________________________________________ __________________________________________________________________ __________________________________________________________________

7 If a switch hears three different configuration BPDUs from three different neighbors on three different interfaces, and if all three specify that Bridge 1 is the root, how does it choose which interface is its root port?

__________________________________________________________________ __________________________________________________________________ __________________________________________________________________

8 Assume that a building has 100 devices attached to the same Ethernet. These users then are migrated onto two separate shared Ethernet segments, each with 50 devices, with a transparent bridge in between. List two benefits that would be derived for a typical user. __________________________________________________________________ __________________________________________________________________ __________________________________________________________________

9 Define the term broadcast domain.

__________________________________________________________________ __________________________________________________________________ __________________________________________________________________

10 Describe the benefits of creating three VLANs of 25 ports each, versus a single VLAN of 75 ports, in each case using a single switch. Assume that all ports are switched ports (each port is a different collision domain).

__________________________________________________________________ __________________________________________________________________ __________________________________________________________________

“Do I Know This Already?” Quiz 133

11 If two Cisco LAN switches are connected using Fast Ethernet, what VLAN trunking

protocols could be used? If only one VLAN spanned both switches, is a VLAN trunking protocol needed?

12 Define the term VLAN.

13 How many IP addresses must be configured for network management on a Cisco Catalyst

1900 switch if eight ports are to be used with three VLANs?

14 What Catalyst 1900 switch command displays the version of IOS running in the switch? ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________

15 Configuration is added to the running configuration in RAM when commands are typed

in Catalyst 1900 configuration mode. What causes these commands to be saved into NVRAM?

16 Name the three VTP modes. Which of these does not allow VLANs to be added or

modified?

134 Chapter 4: Bridges/Switches and LAN Design

The answers to the quiz are found in Appendix A, “Answers to the ‘Do I Know This Already?’ Quizzes and Q&A Sections,” on page 715. The suggested choices for your next step are as follows:

•

8 or less overall score—Read the entire chapter. This includes the “Foundation Topics” and “Foundation Summary” sections and the Q&A section at the end of the chapter.

•

2 or less on any quizlet—Review the subsection(s) of the “Foundation Topics” part of this chapter, based on Table 4-1. Then move into the “Foundation Summary” section and the Q&A section at the end of the chapter.

•

9 to 12 overall score—Begin with the “Foundation Summary” section, and then go to the Q&A section and the scenarios at the end of the chapter.

•

13 or more overall score—If you want more review on these topics, skip to the “Foundation Summary” section, and then go to the Q&A section at the end of the chapter. Otherwise, move to the next chapter.

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