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- Herausgeber: Packt Publishing
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Become familiar with ICND1 (100-105) exam objectives, and learn how to get ready for the exam
Key Features
- A step by step guide that will build you skills from basic concepts to completely understanding network communication
- Comprehensive coverage to help you implement the knowledge you've gained in real-world scenarios
- Take practice questions and mock tests to check how prepared you are for the CCENT exam
Book Description
CCENT is the entry-level certification for those looking to venture into the networking world. This guide will help you stay up-to date with your networking skills. This book starts with the basics and will take you through everything essential to pass the certification exam. It extensively covers IPv4 and IPv6 addressing, IP data networks, switching and routing, network security, and much more—all in some detail. This guide will provide real-world examples with a bunch of hands-on labs to give you immense expertise in important networking tasks, with a practical approach. Each chapter consists of practice questions to help you take up a challenge from what you have procured. This book ends with mock tests with several examples to help you confidently pass the certification. This Certification Guide consists of everything you need to know in order to pass the ICND 1 100-105 Exam, thus obtaining a CCENT certification. However, practicing with real switches and routers or a switch or router simulator will help you succeed.
What you will learn
- Get to grips with the computer network concepts
- Understand computer network components and learn to create a computer network
- Understand switching and learn how to configure a switch
- Understand routing and learn how to configure a router
- Understand network services and the maintenance process
- Learn how to troubleshoot networking issues
- Become familiar with, and learn how to prepare for, the ICND1 100-105 exam
Who this book is for
If you are a Network Administrator, Network Technician, Networking professional, or would simply like to prepare for your CCENT certification, then this book is for you. Some basic understanding of networks and how they work would be helpful. Sufficient information will be provided to those new to this field.
Bekim Dauti works mainly with the administration of computer systems and networks, as well as vocational training in Cisco and Microsoft technologies. Bekim has a bachelor's degree from the University of Tirana and a master's from UMUC Europe, both in information technology. Additionally, he holds several IT certifications from vendors such as ECDL, MOS, CompTIA, Cisco, Microsoft, and Sun Microsystems. Bekim has contributed to over 10 computer books and dozens of articles for PC World Albanian and CIO Albania. Currently, he works as a system administrator at Kosovo Telecom JSC.Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 356
Veröffentlichungsjahr: 2018
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CCENT/CCNA: ICND1 100-105 Certification Guide
Copyright © 2018 Packt Publishing
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First published: April 2018
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Published by Packt Publishing Ltd. Livery Place 35 Livery Street Birmingham B3 2PB, UK.
ISBN 978-1-78862-143-4
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About the author
Bekim Dauti works mainly with the administration of computer systems and networks, as well as vocational training in Cisco and Microsoft technologies. Bekim has a bachelor's degree from the University of Tirana and a master's from UMUC Europe, both in information technology. Additionally, he holds several IT certifications from vendors such as ECDL, MOS, CompTIA, Cisco, Microsoft, and Sun Microsystems. Bekim has contributed to over 10 computer books and dozens of articles for PC World Albanian and CIO Albania. Currently, he works as a system administrator at Kosovo Telecom JSC.
About the reviewer
Shiva V.N. Parasram is a professional Cyber Security Trainer and the owner of the Computer Forensics and Security Institute (CFSI). He is also a Certified EC-Council Instructor (CEI), and some of his qualifications include an MSc in Network Security (Distinction), CEH, CHFI, ECSA, CCNA, and NSE. He has successfully executed and delivered forensic investigations, penetration tests, and security training for large enterprises, and he is also the author of Digital Forensics with Kali Linux.
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Table of Contents
Title Page
Copyright and credits
CCENT/CCNA: ICND1 100-105 Certification Guide
Dedication
Packt Upsell
Why subscribe?
PacktPub.com
Contributors
About the author
About the reviewer
Packt is searching for authors like you
Preface
Who this book is for
What this book covers
To get the most out of this book
Download the color images
Conventions used
Get in touch
Reviews
Introduction to Computer Networks
From ARPANET to internet
What is a computer network?
Requirements for designing a computer network
Types of computer networks
Personal area network (PAN)
Local area network (LAN)
Metropolitan area network (MAN)
Wide area network (WAN)
Intranet
Extranet
Computer network topologies
Physical topology
Bus
Ring
Star
Extended star
Hierarchical
Mesh
Logical topology
Computer network components
Clients
Servers
Hosts and nodes
Network interface
Peripheral devices
Applications and shared data
Hubs and switches
Routers
Infrastructure components
Firewall
Wireless access point
Wireless access controller
Computer network architectures
Peer-to-peer networking (P2P)
Client/server networking
Network operating system (NOS)
Windows
Linux
macOS X Server
Network medium
Twisted pairs
Coaxial
Fibre optic
Infrared and Bluetooth
Radio waves
Satellite
Converged networks
Growing complexity of networks
Elements of converged networks
Access, distribution, and core layers
Network trends
Summary
Questions
Communication in Computer Networks
How do computers communicate?
Message encoding
Message formatting and encapsulation
Message size
Message timing
Message delivery types
Unicast transmission
Multicast transmission
Broadcast transmission
Types of communication channels
Simplex
Half-duplex
Full-duplex
Communication protocols
Characteristics of communication protocols
Connection-oriented protocols
Connectionless protocols
Circuit switching versus packet switching
Well-known communication protocols
OSI and TCP/IP model overview
TCP/IP protocol model
OSI reference model
OSI layers and their protocols
Physical layer protocols
Data link layer protocols
Network layer protocols
Transport layer protocols
Session layer protocols
Presentation layer protocols
Application layer protocols
Ethernet communication technology
Ethernet history
Ethernet protocols
Ethernet frame
Ethernet MAC addresses
Ethernet's CSMA CD vs. Ethernet's CSMA CA
The IP addresses and subnets
IPv4 network addresses
Public IP addresses
Private IP addresses
Loopback IP address
Automatic Private IP Addressing (APIPA)
Unicast, multicast, and broadcast addresses
Class A addresses
Class B addresses
Class C addresses
Class D addresses
Class E addresses
IPv6 network addresses
Global unicast addresses
Link-local addresses
Unique local addresses
Loopback address
"This host, this network" address
Multicast addresses
Anycast
Autoconfiguration
Subnetting
Classful subnetting
Classless subnetting
IPv6 subnetting
Summary
Questions
Introduction to Switching
What is switch?
Switch essentials
MAC address table
MAC learning and aging
Frame switching
Frame flooding
Switching general concepts
Ingress and egress ports
Source and destination MAC addresses
Unicast MAC address
Multicast MAC address
Broadcast MAC address
Switched networks
The role of switched networks
Features of the switch
Fixed configuration switches
Modular configuration switches
Stackable configuration switches
Frame forwarding methods
Store-and-forward switching
Cut-through switching
Fast-forward switching
Fragment-free switching
Switching domains
Collision domains
Broadcast domains
Network congestion
Switch port settings
Duplex and speed settings
Auto-MDIX
Overview of VLANs
VLAN segmentation
VLANs in a multiswitched environment
VLAN trunks
Inter-VLAN operation
Ethernet's frame overview
Ethernet frame encapsulation
Ethernet frame fields
Ethernet frame processing
Switch security
Secure remote access
Telnet
SSH
Port security operation
Summary
Questions
Setting Up the Switch
Basic switch configuration
Configuration with initial settings
Boot sequence
LED indicators
Connecting to a switch and running initial configuration
Configuring basic management access
Configuring ports
Configuring VLANs
Configuring VLAN trunks
Configuring legacy inter-VLAN routing
Scenario – Router with multiple interfaces
Verifying VLAN information on a switch
Configuring router-on-a-stick inter-VLAN routing
Scenario – Router with a single interface
Verifying VLAN information on a switch
Configuring remote access
Configuring Telnet
Configuring SSH
Configuring switchport security
Summary
Questions
Introduction to Routing
Routing concepts
Understanding host routing
Host forwarding decisions
Default gateway
Host routing tables
Routing operations
Switching packets
Router switching functions
Sending packets
Packet routing
Forward to next-hop
Reaching the destination
Path determination
Routing decision
Selecting the best path
Network Load Balancing (NLB)
Administrative distance (AD)
What is a router?
A router is a computer
Router's CPU and OS
Anatomy of a router
Connecting to a router
LAN and WAN interfaces
Boot up the router
Router's boot up process
Bootset files
Router routing tables
Understanding packet forwarding
IPv4 routing table
Directly connected routing table entries
Remote network routing table entries
Next-hop IP address
Routing types
Static routing
Static route applications
Dynamic routing
Dynamic routing protocols
Routing table terms
Summary
Questions
Setting up the Router
Connecting the router to a PC and turning it on
Router LED indicators
Console access
Turning on the router
Show version output
Router's initial configuration
Configuring basic router settings
Configuring IPv4  and IPv6 addresses on router interfaces
Configuring static routes and default static routes
Configuring IPv4 static routes and default static routes
Configuring IPv6 static routes and default static routes
Configuring Routing Information Protocol (RIP)
InterVLAN configuration
Router-on-a-stick interVLAN configuration
Summary
Questions
Networking Services and Maintenance
Dynamic Host Configuration Protocol overview
Assigning IPv4 addresses dynamically
Configuring DHCPv4
Assigning IPv6 addresses dynamically
Configuring stateless DHCPv6
Configuring Stateful DHCPv6
Network Address Translator overview
Configuring static NAT
Configuring dynamic NAT
Configuring PAT
Configuring port forwarding
NAT and IPv6
Network Time Protocol overview
Configuring and verifying NTP
Cisco Discovery Protocol and Link-Layer Discovery Protocol overview
Device discovery with CDP
Device discovery with LLDP
System logging overview
Configuring syslog
Device maintenance
Router and switch file maintenance
Router file systems
Switch file systems
Backing up and restoring text files
Backing up and restoring to/from TFTP
Using USB ports on a Cisco router
Backing up and restoring to/from a USB flash drive
Password recovery using ROMMON
IOS system files
IOS 15.0 system image packaging
IOS image filename
IOS image management
TFTP servers as a backup location
Steps to back up an IOS image to a TFTP server
Copying an IOS image to a device
The boot system command
 Software licensing
Licensing overview
Licensing process
License verification and management
License verification
Activating an evaluation right-to-use license
Backing up the license
Uninstalling the license
Traffic management
Summary
Questions
Network Troubleshooting
Troubleshooting methodologies
Basic approaches
Resolve or escalate?
Verifying and monitoring solutions
Troubleshooting scenarios
IP addressing issues on networking devices
IP addressing issues on end devices
Default gateway issues
Troubleshooting DNS issues
Troubleshooting cables and interfaces
Cable problems
Duplex operation
Duplex mismatch
Switch troubleshooting
Recovering from a system crash
Network access layer issues
Troubleshooting network access layer issues
Ports in error-disabled state
Router troubleshooting
Verifying IPv4 interface settings
Verifying IPv6 interface settings
The show history command
Troubleshooting a missing route
Solving a connectivity problem
Troubleshooting VLANs
IP addressing issues with VLANs
Troubleshooting Access Control Lists
Processing packets with ACLs
Common IPv4 standard ACL errors
Troubleshooting DHCP
Troubleshooting DHCPv4
Troubleshooting DHCPv6
Troubleshooting NAT
The show ip NAT commands
The debug ip NAT command
Basic network performance
The ping command
The traceroute and tracert commands
The show commands
Command syntax
The debug command
Network security
Security threats and vulnerabilities
Network attacks
Network attack mitigation
Device security
Summary
Questions
Studying and Preparing for ICND 1 (100-105) Exam
What is the ICND 1 (100-105) exam?
What are the ICND 1 (100-105) exam topics?
Topic 1.0–Network fundamentals (20%)
Topic 2.0 - LAN switching fundamentals (26%)
Topic 3.0 -  Routing fundamentals (25%)
Topic 4.0 - Infrastructure services (15%)
Topic 5.0 – Infrastructure maintenance (14%)
What to expect in the ICND 1 (100-105) exam
How to prepare for the ICDN 1 (100-105) exam
How to register for the ICND 1 (100-105) exam?
On the day of the ICND 1 (100-105) exam
Post-ICND 1 (100-105) exam certification path
Appendix A: Answers to Chapter Questions
Chapter 1–Answers
Chapter 2—Answers
Chapter 3—Answers
Chapter 4—Answers
Chapter 5—Answers
Chapter 6—Answers
Chapter 7—Answers
Chapter 8 — Answers
Appendix B: Cisco Device Icons
Cisco network topology icons
Appendix C: Numbering Systems and Conversions
Binary numbering system
Decimal to binary conversion
Binary to decimal conversion
Octal numbering system
Decimal to octal conversion
Hexadecimal numbering system
Decimal to hexadecimal conversion
Appendix D: Boolean Algebra
AND operation
OR operation
NOT operation
Appendix E: Subnetting
Example—Class A subnetting
Example—Class B subnetting
Example—Class C subnetting
Appendix F: Cisco Packet Tracer
Downloading Packet Tracer
Installing Packet Tracer
Appendix G: Graphical Network Simulator-3 (GNS3)
Downloading GNS3
Installing GNS3
Other Books you may enjoy
Preface
CCENT is the entry-level certification for those looking to venture into the networking world. This guide will help you stay up to date with your networking skills. This book starts with the basics and will take you through everything you need to pass the certification exam. It extensively covers IPv4 and IPv6 addressing, IP data networks, switching and routing, network security, and much more—all in some detail. This guide will provide real-world examples with a bunch of hands-on labs to give you immense expertise in important networking tasks, with a practical approach. Each chapter consists of practice questions to help you take up a challenge from what you have procured. This book ends with mock tests with several examples to help you confidently pass the certification. This Certification Guide consists of everything you need to know in order to pass the ICND 1 100-105 exam, thus obtaining a CCENT certification. However, practicing with real switches and routers or a switch or router simulator will help you succeed.
Who this book is for
If you are a Network Administrator, Network Technician, Networking professional, or would simply like to prepare for your CCENT certification, then this book is for you. Some basic understanding of networks and how they work would be helpful. Sufficient information will be provided to those new to this field.
What this book covers
Chapter 1, Introduction to Computer Networks, will teach you about the general concepts of computer networks. In addition, the reader will learn how to build a computer network.
Chapter 2, Communication in Computer Networks, will help you understand about communication protocols in computer networks. In addition, the reader will learn about OSI and TCP/IP reference models, IP addressing, IP subnetting, and Ethernet communication technology.
Chapter 3, Introduction to Switching, will make you familiar with the switch as an intermediary networking device. At the same time, the reader will learn how switches operate and how to connect a switch to a network.
Chapter 4, Setting Up the Switch, will provide an explanation of how to configure a switch in a step-by-step manner.
Chapter 5, Introduction to Routing, will make you familiar with the router as an intermediary networking device. At the same time, you will learn how routers function and how to connect a router to a network.
Chapter 6, Setting Up the Router, will help you understand how to configure a router in a step-by-step manner.
Chapter 7, Network Services and Maintenance, will teach you about the network service and how to enable services on a computer network. In addition, you will become familiar with maintenance process, and you will learn how to maintain the computer network's performance.
Chapter 8, Network Troubleshooting, will help you understand troubleshooting, and then you will be able to rectify errors and problems in computer networks.
Chapter 9, Studying and Preparing for the ICND 1(100-105) Exam, will make you familiar with ICND 1 (100-105) exam and learn how to prepare for and pass it in a simple and convenient way.
Appendix A, Answers to Chapters Questions, contains chapter wise answers to the questions mentioned in the chapters.
Appendix B, Cisco Device Icons, represents the symbols that are used in Cisco Network Topology.
Appendix C, Numbering Systems and Conversions, explains the binary, octal and hexadecimal numbers along with conversions from decimal to binary, octal and hexadecimal.
Appendix D, Boolean Algebra, explains the boolean operations.
Appendix E, Subnetting, explains the method of subnetting using examples.
Appendix F, Cisco Packet Tracer, explains the installation of Cisco Packet Tracer.
Appendix G, Graphical Network Simulator-3 (GNS-3), explains installation of GNS-3.
To get the most out of this book
To understand the content of this book, it is recommended that you have basic knowledge in computer networks. If you are certified with CompTIA Network +, that would be a good foundation for you to advance your knowledge about computer networks through this book.
As you know, it does not make sense to learn computer networks without doing any practical work. Therefore, the suggestions are to practice making cables such as straight through, crossover, and roll over. Setting up a LAN with at least a Cisco switch and router. And download emulators and simulators like Putty and Tera Term, Packet Tracer and GNS3, and Wireshark. All the download links are included on the book.
Download the color images
We also provide a PDF file that has color images of the screenshots/diagrams used in this book. You can download it from https://www.packtpub.com/sites/default/files/downloads/CCENTCCNAICND1100105CertificationGuide_ColorImages.pdf.
Conventions used
There are a number of text conventions used throughout this book.
CodeInText: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: "In the privileged EXEC prompt, enter the show running-config (or show startup-config) command and press Enter."
Any command-line input or output is written as follows:
C:\>
ping 127.0.0.1
Bold: Indicates a new term, an important word, or words that you see onscreen. For example, words in menus or dialog boxes appear in the text like this. Here is an example:
In Windows 10, click Yes to let the app make changes to your device:
Get in touch
Feedback from our readers is always welcome.
General feedback: Email [email protected] and mention the book title in the subject of your message. If you have questions about any aspect of this book, please email us at [email protected].
Errata: Although we have taken every care to ensure the accuracy of our content, mistakes do happen. If you have found a mistake in this book, we would be grateful if you would report this to us. Please visit www.packtpub.com/submit-errata, selecting your book, clicking on the Errata Submission Form link, and entering the details.
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Introduction to Computer Networks
This chapteris designed to provide you with an introduction to computer networks. It begins with the evolution of Advanced Research Projects Agency Network (ARPANET) to the internet, and then continues with the explanation of the computer network concept. This chapter discusses the types of networks, topologies, components, architectures, network operating systems (NOSs), and network media where definitionssuch as personal area network (PAN), local area network (LAN), metropolitan area network (MAN), wide area network (WAN), bus, ring, star, extended star, hierarchical, mesh, hosts, nodes, peer-to-peer, and clients/servers are explained. The chapter concludes with a discussion about converged networks, and the current and future computer network trends. To facilitate the understanding of the many definitions covered in this chapter, a large part of the definitions are illustrated with relevant figures.
In this chapter, we will cover:
Understanding ARPANET and the internet
Understanding computer networks
Understanding types of computer networks
Understanding computer network topologies
Understanding computer network components
Understanding computer network architectures
Understanding network operating systems
Understanding network medium
Understanding converged networks
Understanding computer network trends
From ARPANET to internet
No one can explain the history of the internet better than the internet itself! Everything started with the US government's project to build a stable and tolerant-in-defects communication network known as the Defense Advanced Research Projects Agency (DARPA). The involvement of research centers and academic institutions in the DARPA project made this project gradually evolve into the ARPANET and the Military Network (MILNET). While the MILNET project was tasked to support operational requirements, the ARPANET project was undertaken to support the need for research (https://www.internetsociety.org/). That said, from 1962 to 1985, the internet already had built its profile. Thus, based on the saying "every new beginning is some beginning’s end", the appearance of the internet on the global computer network stage formally marked the end of the ARPANET's golden era.
According to the internetsociety.org, on October 24, 1995, the Federal Networking Council (FNC) through a resolution, priory consulted with members of the internet community and intellectual property rights, defined the term internet. According to that resolution, the internet refers to the global information system, which:
Is logically connected by a global unique address space based on the
Internet Protocol
(
IP
) or its subsequent updates;
Is able to support the communication through a TCP/IP protocol suite or its subsequent updates and other compatible protocols, and;
Provides, uses and makes accessible, either publicly or privately, high-level layered services on the communications and related infrastructure described in that document.
Over time, the development and advancement of computer network technologies took place. Thus, the need to connect and interconnect more computers to computer networks, and with it, more geographical locations, created a need for well-defined terms and concepts to describe computer networking. Because of this, types of computer networks, computer network topologies, computer network architectures, and computer network components were born. Certainly, a computer network represents one of the biggest inventions of mankind in the field of communications. Simply, mention theinternetand one will immediately understand how huge the benefit of a computer network is to humanity.
What is a computer network?
Before defining computer network, let’s first look at the general term of a network in order to then recognize the computer network definition in particular. If you do a search for the word network in the Merriam-Webster dictionary, you’ll find the definition that a "network is a group of people or organizations that are closely linked and that work with each other." On the same Merriam-Webster dictionary, the phrase networking is defined as "exchange of information or services among individuals, groups or institutions." Both of these definitions will serve us in a simple, clear, and concrete way to define computer network in the following paragraph.
From what was said in the preceding paragraph, a computer network is a group of computers connected to each other in order to share resources. When talking about resources, usually the resources can be data, network services, and peripheral devices. So, anyone who has experience with computer networks has seen that it is very easy to share files, applications, printers, and other peripheral devices in computer networks. Figure 1.1 presents an example of a computer network:
Requirements for designing a computer network
Of course, the most beautiful part of a computer network is how to design and build one. Computer network design and deployment is Designing and deploying is linked to its definition. Thus, the fundamental requirement for designing a computer network is that there must be two or more computers. Depending on the number of computers on the network and how they access the resources from the same network determines the categorization of computer network types, which will be explained in the following section.
Types of computer networks
Over time, the desire to implement the first computer network, as a result of curiosity, had already been converted to a need that would fulfill the requirements. Precisely, it also led to the development and advancement of computer networking technologies. Thus, the need to connect and interconnect more computers into computer networks, and with it, more locations, in itself resulted as the need to define topologies, architectures, technologies, and computer networking categories. In this way, the types of computer networks like PAN, LAN, MAN, and WAN were born.
Personal area network (PAN)
A PAN is defined as a computer network that is used to connect and transmit data among devices located in a personal area, usually over Bluetooth or Wi-Fi to interconnect devices (see Figure 1.2). Occasionally, this computer network is called a home area network (HAN) too:
Local area network (LAN)
To understand the LAN, let's compare it with the PAN. A PAN is dominated by portable devices (for example, smartphone), while a LAN mainly consists of fixed devices. Both computer networks are covering the local area; however, the LAN has a greater coverage than the PAN, because the LAN usually can cover the floor of the building, several floors of the building, an entire building, or even a few buildings that are close to one another. From that, the main difference is that a PAN is mainly organized around an individual, while a LAN is organized around an organization, business, or legal entity. This then precisely defines the LAN as a computer network that connects two or more computers in a local area for the purpose of sharing resources, as in Figure 1.1.
Metropolitan area network (MAN)
From the standpoint of coverage, the MAN is bigger than the LAN and smaller than the WAN, whilst from the viewpoint of data transmission speeds, the MAN is faster than both the LAN and WAN. As it was with the PAN and LAN, the reason for the MAN's existence is the need for sharing and accessing the resources in the city or metro. From that, a MAN represents a group of LANs interconnected within the geographical boundary of a town or city, as in Figure 1.3:
Wide area network (WAN)
Areas that are not covered by a LAN or MAN are covered by a WAN. Thus, a WAN is a computer network that covers a wide geographic area using dedicated telecommunication lines such as telephone lines, leased lines, or satellites. That being said, unlike other computer networks which have geographic restrictions of their physical reach, WAN does not. From that, it is obvious that WANs are made up of PANs, LANs, and MANs (see Figure 1.4). With that in mind, the best example of a WAN is the internet:
Intranet
The intranet is a networking platform primarily designed for employees. That said, it is considered to be the private network of an organization where employees can access network services. The intranet is not just a portal; instead, it is a network that consists of hardware and software too. To better understand it, consider the intranet as an organization's extended LAN, or MAN, or even WAN network. It consists of multiple cables, network devices such as switches, routers, microwave and satellite antennas, access points, servers, computers, and various applications. All that enables employees to communicate, develop content, collaborate in joint projects, and get the job done.
Extranet
In contrast, the extranet can be thought of as an intranet with a controlled access. Like the intranet, the extranet is a networking platform too; however, besides employees, the extranet enables controlled access to an organization's intranet for authorized partners, suppliers, customers, or others business-related individuals and organizations outside the company. Specifically, the extranet represents a controlled access method of the organization's intranet using internet infrastructure.
Computer network topologies
Another way to categorize computer networks is by their topology, or the way in which hosts and nodes are arranged and connected to one another, and how they communicate. The computer network mainly recognizes two types of topologies: physical, and logical.
Physical topology
Physical topology presents ordering, arrangement, and placement of the physical parts of a computer network, such as computers, peripheral devices, cables for data transmission, and network equipment. Thus, the physical topology of the computer network actually represents its physical structure, which is usually presented in the following shapes: bus, ring, star, extended star, hierarchical, and mesh.
Bus
Bus is the physical topology in which computers, peripheral and network devices are connected through the bus that mainly consists of a coaxial cable (see Figure 1.5):
Ring
Ring is the physical topology in which computers, peripheral and network devices form a closed cycle that takes the shape of a ring network where each device is connected to each other (see Figure 1.6). In the past, the coaxial cable was used, but nowadays in dual ring networks, optical fiber is used:
Star
Star is the physical topology in which computers, peripheral and network devices are connected independently with a central device (see Figure 1.7). For this type of topology, mainly a twisted pair cable is used:
Extended star
Extended star is the physical topology in which computers and peripheral and network devices are connected into two or more star topology networks and then the central components (that is, switches) are interconnected over a bus. In appearance, this type of topology combines star and bus topologies (see Figure 1.8). Mainly, a twisted cable pair is used for the star topology, while an optical fiber is used for the bus topology:
Hierarchical
Hierarchical is the physical topology that represents a combination of star and bus topologies. This topology must have at least three levels of hierarchy in which star topologies connect one or more nodes to a single main node, so that all these together are related to the main trunk of the tree (see Figure 1.9). As in the case of an extended star topology, this topology uses twisted pair cables and optical fiber:
Mesh
Mesh is the physical topology in which each computer is connected with every computer to form the network (see Figure 1.10). Usually, this type of topology is utilized by a WAN to interconnect LANs:
Logical topology
Unlike physical topology, logical topology represents the logical aspect of the computer network. In logical topology, it is the logical paths that are used to carry electric or light signals from one computer to another, or from one network node to another node. Thus, this topology represents the way in which the data accesses the transmission medium and transmits packets through it. Figure 1.11 presents the logical topology with its logical components such as computer names, network equipment, network communication technology, and IP addresses:
Computer network components
Obviously, when talking about computer networks it is essential to mention components of a computer network, because computer networks are ultimately composed of their constituent components. Usually, computers and peripheral devices are just some of the computer network components known to most people; however, there are also intermediary devices and network media.
Knowing that the primary purpose of the computer networks has to do with sharing resources, it is very important to understand the process of how the resources are both shared and accessed. Here comes into play the concept of the client and the server, where the client is the one that always requests resources, and the server is the one that provides the requested resources. To better understand clients and servers, as well as the concept of requesting and providing resources, the following sections explain the network components.
Clients
Now, going back to the concepts of requesting a resource and providing a resource, actually, that is what is shaping the definition of clients and servers in the computer network. Clients, in most cases, are computers that request the resources in a computer network. Clients have an active role in the computer network (see Figure 1.11).
Servers
Furthermore, servers are network components that provide resources to clients.Servers too have an active role. The following figure, Figure 1.1, presents the server with ashared printer in the role of the resource provider, and the PC and laptop in the role of resourcerequesters.
Hosts and nodes
When talking about hosts and nodes, although their first impression might drive us towards thinking that they are the same thing, in fact they are not! The difference between hosts and nodes is that, while all hosts can be nodes, not every node can act as ahost. That way, to every host there is an assigned IP address.So, a host is any device with an IP address that requests or provides networking resources to any other host or nodeon the network; however, there are devices such as hubs, bridges, switches, modems, and access points that have no IP address assigned, but are still used for communications. That said, a node is any device that can generate, receive, and transmit the networking resources on the computer network but has no interface with an IP address. Based on that, in Figure 1.1, server, smartphone, PC, and laptop are hosts, while switch and Access Point (AP) act as nodes.
Network interface
A network interface is a component-like network card or LAN port on network equipment that enables clients, servers, peripheral devices, and network equipment to get connected and communicate with each other. The network interface has both a passive and an active (manageable network equipment) role in the computer network (see Figure 1.12):
Peripheral devices
Peripheral devices are printers, scanners, storage area networks (SANs), and any other peripheral device that provides resources to clients, either through a LAN or as a shared device on a network. These devices play both a passive and an active (like SAN and NAS) role in the computer network:
Applications and shared data
Applications and shared data are virtual network components that represent applications and files shared on the network that are usually provided by servers. These components themselves play a passive role in the computer network, but the server that hosts these services plays an active role in the computer network.
Hubs and switches
Hubs and switches are acting as central components (in Ethernet communication technology) of the computer network to enable interconnection and communication between clients, servers, and peripheral devices, as in Figure 1.14 . Most hubs are passive devices, while switches play an active role in the computer network:
Routers
Routers (see Figure 1.15) are computer network components that enable routing of the data (that is, packets) from a LAN to the internet, and vice versa. Routers have an active role in the computer network:
Infrastructure components
Network infrastructure is also the part of the discussion when we discuss about network components. So, of course, the question is, what is network infrastructure?In its simple format the answer would be that network infrastructure is any physical and logical network component that enables connection, communication, operation, management, and security of the network.
Firewall
No matter what professional background you might have, it is just enough to get to know the name of the firewall and you will immediately think that there is no joke with such device. Leaving the humor aside, a firewall (see Figure 1.16) is a network device that provides security to the network infrastructure. It does so by controlling and monitoring both incoming and outgoing traffic based on configured security rules. In a nutshell, the firewall to a network infrastructure is like a security officer at an organization's main gate:
Wireless access point
Nowadays, we often hear expressions like "I got connected to the internet with wireless" or "I've found an open wireless." This and many other similar expressions make us understand that the discussion is about the access point. That said, an AP (see Figure 1.17), often known as a wirelessaccess point, is a network device that enables access to the wired network. With APs in a network infrastructure, the network becomes more accessible by enabling the access to organization services while on the go. In addition, it enables the support for the new trends like Bring Your Own Devices (BYOD):
Wireless access controller
Since network infrastructure has many network devices, including APs for the security purposes as well as for the quality of services (QoS), organizations will employ a wireless access controller. It is a networking device that enables organizations to centrally manage APs.
Computer network architectures
When talking about computer networks, actually we are talking about the essential and broader concept of the elements that make up a computer network. In this form of discussion, while the computer network types deal with the area coverage, the physical and logical topologies deal with the physical arrangement and logical structure of the computer network. Having said that, the computer network architecture represents the computer network design that allows the computer network components to communicate with one another.
Peer-to-peer networking (P2P)
Peer-to-peer is a computer network in which the participating computers do not play the predefined roles in the network, but instead they change roles from client to server, and vice versa, based on the actual activity on the network. For example, if computer A is accessing resources from computer B, then computer A acts as the client, while computer B acts as the server. After some time, if computer B accesses resources from computer A, then computer B becomes a client and computer A becomes a server. As you may notice, they switch roles based on who is requesting and who is providing a resource on the network. Figure 1.18 presents an example of peer-to-peer networking:
Client/server networking
Client/server is a computer network in which participating computers have a predefined role. That means that, in this computer network architecture, computers that access resources act as clients, while computers that provide resources act as servers. In general, this is a computer network architecture with dedicated servers that provide resources on the network. Midsize and enterprise computer networks are the best example of the client/server computer network. Figure 1.19
