Cisco Networking Essentials

Troy McMillan

• Publisher: Sybex
• Year: 2015
• ISBN:
  9781119092131
• Edition: 2
• Topic: Informatique
• Subtopic: Réseaux informatiques

Start a career in networking

Cisco Networking Essentials, 2 nd Edition provides the latest for those beginning a career in networking. This book provides the fundamentals of networking and leads you through the concepts, processes, and skills you need to master fundamental networking concepts. Thinking of taking the CCENT Cisco Certified Entry Networking Technician ICND1 Exam 100-101? This book has you covered! With coverage of important topics and objectives, each chapter outlines main points and provides clear, engaging discussion that will give you a sound understanding of core topics and concepts. End-of-chapter review questions and suggested labs help reinforce what you've learned, and show you where you may need to backtrack and brush up before exam day.

Cisco is the worldwide leader in networking products and services, which are used by a majority of the world's companies. This book gives you the skills and understanding you need to administer these networks, for a skillset that will serve you anywhere around the globe.

• Understand fundamental networking concepts
• Learn your way around Cisco products and services
• Gain the skills you need to administer Cisco routers and switches
• Prepare thoroughly for the CCENT exam

If you're interested in becoming in-demand, network administration is the way to go; if you want to develop the skillset every company wants to hire, Cisco Networking Essentials, 2 nd Edition gets you started working with the most widespread name in the business.

Chapter 1
Networks

Computer networks are everywhere. It's impossible to escape them in the modern world in which we live and work. We use them at work, at home, and even in between, in places like our cars, the park, and the coffee shop. We have come to take them for granted in the same way we treat electricity and hot water.

But a lot is going on behind the scenes when we use these networks. Cisco routers and switches play a critical role in successful network operation.

This opening chapter lays the foundation required to understand all the details that make networks function. Specifically, this chapter covers the following topics:

• Describing network components
• Classifying networks by function
• Defining network architectures

Describing Network Components

To understand how networks work, it helps to have an appreciation of why they exist in the first place. As incredible as it may seem now, for a number of years when computers first came into use, very few computers were networked. They operated as little islands of information with no connection to one another. Data had to be transferred between computers by copying it to a floppy disk, physically taking that floppy disk to the other computer, and copying the data to the destination machine. This process is now sometimes jokingly referred to as the sneakernet.

Modern networks can include many components. Some of the most basic components are computers, routers, and switches. Figure 1.1 shows some Cisco routers and switches. Routers are used in a network to transfer information between computers that are not on the same network. Routers are capable of doing this by maintaining a table of all networks and the routes (directions) used to locate those networks. Switches come in two varieties: layer 2 and layer 3. Layer 2 switches simply connect computers or devices that are in the same network. Layer 3 switches can do that but are capable of acting as routers as well. Two models of routers are depicted in Figure 1.1, with a switch in the middle of the stack. Routers and switches are covered in depth in Chapter 10, “Network Devices.”

Figure 1.1 Cisco routers and switches

In this section, the benefits of networking are covered as well as the components required to constitute a network.

Defining the Benefits of Networks

There are many benefits to networks, one of which was touched on in the introduction to this section: using a network makes sharing resources possible (without putting on your sneakers and leaving your seat). When connected by networks, users can share files, folders, printers, music, movies—you name it! If it can be put on a hard drive, it can be shared. Additional benefits are included in the following list:

1. Resource Sharing Resource sharing is less earthshaking at home, but in the workplace, it was a key element that drove the adoption of PCs. Other computer types such as mainframe computers and dumb terminals were already in use, but were seen as specialized pieces of equipment to be used only by guys in lab coats and some other geeky types. There were other reasons for the PC revolution, but resource sharing helped to increase productivity. As an example, 10 coworkers could access a file on the network at the same time, which eliminated the time and effort spent burning, labeling, transporting, and storing 10 floppies.

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   The term resource is used extensively when discussing networking and simply refers to anything that a user on one computer may want to access on a different computer. Examples include files, folders, printers, and scanners.

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2. Reduced Cost and Easier Installation of Software Although it didn't become apparent as quickly as resource sharing did, a reduced cost of software is another advantage. Many software products are sold to organizations on a network basis. For example, instead of buying 25 retail versions of word-processing software, a single copy can be purchased for the network and then a number of seat licenses can be added to the bundle. The result is a significant savings to the company.
   Taking that idea a step further, the network also makes it possible to place the installation files (from the CD containing the software) on a server and then install the software over the network (as shown in Figure 1.2). This capability relieves IT staff from having to physically visit each machine with CD in hand to perform the installation. Moreover, the software can be installed on all five machines at once over the network by using those same files.

   

   Figure 1.2 Network installation

3. Improved Security All this peace, love, and sharing doesn't mean that everything is available to everyone. Shared resources can be secured with restrictions on who can access them and what exact access each individual possesses. So you can share a file on your computer but share it with only two of your coworkers, not all of them. Moreover, you could allow one coworker to only read the document, while the other could be allowed to edit or even delete the document.
   This type of control was difficult when files ...