Comptia N+ Standard Networking lesson guide

Networking
COMPTIA N+ STANDARD

Course Outline
 Introduction to Networking
Course overview and expectations.
Importance of networking in IT.
Networking Basics
Definition and types of networks.
Networking components: routers, switches, hubs.
Common network protocols.
OSI Model
Introduction to the OSI model.
Functions of each OSI layer.
Examples of protocols at each layer.

Course Outline
Network Infrastructure
Understand the components and technologies used in network infrastructure.
Network Topologies
Overview of network topologies.
Advantages and disadvantages.
Physical vs. logical topologies.
Networking Devices
Routers, switches, hubs, and bridges.
Functions and configurations.
Troubleshooting common issues.
Subnetting
Basics of subnetting.
Subnetting calculations.
Subnetting practice exercises.

Course Outline
Network Protocols
Explore common network protocols and their functions.
TCP/IP Fundamentals
Overview of TCP/IP.
IPv4 vs. IPv6.
TCP and UDP differences.
DHCP and DNS
DHCP concepts and configuration.
DNS concepts and resolution process.
Troubleshooting DHCP and DNS issues.
HTTP, HTTPS, FTP
Understanding web protocols.
Configuration and troubleshooting.
Introduction to secure protocols.

Course Outline
Network Security
Introduce basic network security concepts and measures.
Introduction to Network Security
◦ Importance of network security.
◦ Common network security threats.
◦ Security best practices.
Firewalls and VPNs
◦ Firewall concepts and types.
◦ VPN basics and configurations.
◦ Implementing security policies.
Wireless Security
◦ Wireless network vulnerabilities.
◦ WPA, WPA2, and WPA3.
◦ Configuring wireless security.

Course Outline
Troubleshooting and Maintenance
Learn the skills to troubleshoot and maintain network infrastructure.
Network Troubleshooting
◦ Troubleshooting methodology.
◦ Common network issues and solutions.
◦ Use of network troubleshooting tools.
Network Maintenance
◦ Regular maintenance tasks.
◦ Firmware updates and patches.
◦ Backup and recovery procedures.
Practice Exam and Review
◦ Distribute practice exams.
◦ Review key concepts and troubleshoot problem areas.

Introduction to Networking
In today's digital age, networking is the backbone of communication and information exchange.
Networks enable computers, devices, and systems to connect and share resources, fostering
collaboration and efficiency.
Understanding Networking
What is a computer network?
At its core, a network is a collection of interconnected devices—computers, servers, routers,
switches, and more—that communicate with each other. These connections can exist within a
local environment, such as a home or office, or extend globally through the internet.
Computers and Services are connected for the purpose of sharing resources
More efficient than stand alone systems
It is the foundation of communication

Introduction to Networking
Computer networks vary in type based on various factors
Location of connected systems
Size
Administrative control
Centralized or Decentralized management
Legacy and modern equipment

Network Building Blocks
Regardless of the actual type of network, all networks have common components
Node or Host
◦ Network Interface Card (NIC)
Resources
◦ Files
◦ Applications
◦ Services
Clients
Servers
Media
Devices

Types of Networks
Local Area Network (LAN):
Definition: A LAN is a network that is limited to a small geographic area, such as within a single
building or campus.
WLAN: Wireless Local Area Network
PAN: Personal Area Network
SAN: Storage Area Network
Wide Area Network (WAN):
Definition: A WAN covers a broader geographical area and connects multiple LANs, often across
cities or countries.
MAN
CAN
SDWAN

Intranet Vs Extranet
An intranet is a private network within an organization that uses internet protocols and
technologies.
Internal Communication, Collaboration and information sharing.
Extranet
Extends a portion of an organization's intranet to external entities.
Enables secure collaboration beyond organizational boundaries.

Could-Based Network
Definition: Cloud-based networks utilize cloud infrastructure to provide scalable and flexible
networking solutions.
Characteristics:
Resources are hosted and managed in the cloud.
Allows for on-demand scaling of network resources.

Cloud Computing
Cloud Computing provides a means by
which we can access the applications as
utilities, over the Internet. It allows us to
create, configure, and customize
applications online.
With Cloud Computing users can access
database resources via the internet from
anywhere for as long as they need
without worrying about any maintenance
or management of actual resources.

What is Cloud?
The term Cloud refers to a Network or Internet. In other words, we can say that Cloud is
something, which is present at remote location Cloud can provide services over network.
i.e., on public networks or on private networks, i.e., WAN, LAN or VPN.
Applications such as e-mail, web conferencing, customer relationship management (CRM),
all run in cloud.

What is Cloud Computing?
Cloud Computing refers to manipulating, configuring, and accessing the applications online.
It offers online data storage, infrastructure and application.
Cloud Computing is both a combination of software and hardware based computing
resources delivered as a network service.

Concepts of Cloud computing
Certain services and underlying models operate in the background to
enable the feasibility and accessibility of cloud computing for end
users. The following outlines the operational models for cloud
computing:
1. Deployment Models
2. Service Models

Deployment models
Deployment models define the type of access to the
cloud, i.e., how the cloud is located? Cloud can have
any of the four types of access: Public, Private, Hybrid
and Community.

• PUBLIC CLOUD: The Public Cloud allows systems and services
to be easily accessible to the general public. Public cloud may
be less secure because of its openness, e.g., e-mail.
• PRIVATE CLOUD: The Private Cloud allows systems and services
to be accessible within an organization. It offers increased
security because of its private nature
• COMMUNITY CLOUD: The Community Cloud allows systems
and services to be accessible by group of organizations.
• HYBRID CLOUD: The Hybrid Cloud is mixture of public and
private cloud. However, the critical activities are performed
using private cloud while the non-critical activities are
performed using public cloud.

Service Models
Service Models are the reference models on which the
Cloud Computing is based. These can be categorized
into three basic service models:
1. Infrastructure as a Service
2. Platform as a Service
3. Software as a Service

Infrastructure as a Service(IaaS)
laas is the delivery of technology infrastructure as an on demand scalable service.
laas provides access to fundamental resources such as physical machines, virtual
machines, virtual storage, etc.
Usually billed based on usage
Usually multi tenant virtualized environment
Can be coupled with Managed Services for OS and application support

Comptia N+ Standard Networking lesson guide

Advantages
ADVANTAGES DISADVANTAGES
Lower computer costs Requires a constant Internet connection
Improved performance Does not work well with low-speed connections
Reduced software costs Features might be limited
Instant software updates Can be slow
Improved document format compatibility Stored data can be lost
Unlimited storage capacity Stored data might not be secure
Increased data reliability
Universal document access
Device independence

Host Requirements
•Connection:
• NICs are generally embedded onto the motherboard of all modern desktops and included
with all laptops, but could be added via USB or PCI interfaces if required
• Contain a transceiver
• Matched with the media in use on the network
•Client
• The appropriate network client must be installed in order to communicate with the NOS
running on the servers and in order to share resources with other networked computers
•Protocol
• Language that computers, servers, and other network devices use to communicate with one
another

Numbering Systems
Binary – 1010 1011
◦ Base 2 Numbering system
Decimal – 171
Base 10 numbering system
Hexadecimal – AB
Base 16 numbering system

Communication Types
Communication over the network occurs in three ways
•Unicast
◦ One-to-One
Multicast
◦ One-to-Many
Broadcast
◦ One-to-all

Networks Models and Topologies
The term NETWORK MODEL is used to describe the type of network as it relates to the methods
of administration and types of systems.
Peer-to-Peer(Workgroup)
 Decentralized security and administration
 Any types of devices can be used and share data
 Simple to setup and manage
 Client – Server (domain)
 Centralized security and administration
 Requires additional planning and ongoing administration
 Sharing is generally done by dedicated servers

Workgroup vs. Domain
Peer-to-Peer (Workgroup) Client - Server (Domain)
Security handled at each workstation Security is handled on domain controllers
Requires accounts on each device or shared
accounts
Single sign-on (SSO)
Security is limited Security is maximized
Configuration management is local Configuration management is centralized
Practical only for very small environments Scalable to enterprise level environments

Network Topologies
Network topology refers to the arrangement of nodes and the interconnections between them
in a computer network. Different network topologies are suitable for different scenarios,
depending on factors such as the size of the network, the degree of fault tolerance required, and
the cost considerations.

Bus Topology
A Bus topology consists of a single cable-called a bus- connecting all nodes on a network
without intervening connectivity devices

Advantages
Works well for small networks.
Relatively inexpensive to implement.
Easy to expand joining two cables together.
Used in small network.
Disadvantages of Bus Topology
Management costs can be high
When cables fails then whole network fails.
Cables has a limited length.

Star Topology
A star network is designed with each node (file server, workstation, peripheral) connected
directly to a central network hub or server.

Advantages of Star Topology
 Good option for modern networks
 Low startup costs
Easy to manage
Offers opportunities for expansion
Most popular topology in use wide variety of equipment available
Disadvantages of Star Topology
Hub is a single point of failure
Requires more cable than the bus
Cost of installation is high.

Ring topology
A ring network is one where all workstations and other devices are connected in a
continuous loop. There is no central server.

Advantages of Ring topology
Easier to manage; easier to locate a defective node or cable problem
Well-suited for transmitting signals over long distances on a LAN
Handles high-volume network traffic
Disadvantages
Expensive
Requires more cable and network equipment at the start
Not used as widely as bus topology
Fewer equipment options
Fewer options for expansion to high-speed communication

Tree topology
It has a root node and all other nodes are connected to it forming a hierarchy. It is also
called Hierarchical Topology.

Advantages Of Tree Topology
Extension of Bus and Star Topology.
Expansion of nodes is possible and easy.
Easily managed and maintained.
Disadvantages
Heavily cabled.
Costly.
If more nodes are added maintenance is difficult.
Central hub fails, network fails.

Mesh Topology
It is a point-to-point connection to other nodes or devices. Traffic is carried only between
two devices or nodes to which it is connected.

Advantages Of Mesh Topology
Each connection can carry its own data load.
Fault is diagnosed easily.
Provide security and privacy.
Disadvantages
Installation and configuration is difficult.
Cabling cost is more.
Bulk wiring is required.

Hybrid Topology
It is the mixture of two or more topologies. Therefore it is called Hybrid topology. A
hybrid topology combines characteristics of linear bus and star and/or ring topologies.

Advantages of hybrid topology
Reliable as error detecting and trouble shooting is easy.
Effective.
Scalable as size can be increased easily.
Flexible.
Disadvantages Of Hybrid Topology
Complex in design.
Costly.

Wireless Topologies
Wireless topologies refer to the arrangement or configuration of wireless devices and their
connections in a wireless network. Unlike wired networks, where devices are physically
connected through cables, wireless networks rely on radio waves or infrared signals for
communication.

Ad-Hoc (Peer-to-Peer) Topology:
In an ad-hoc topology, wireless devices communicate directly with each other without the need
for a central access point (AP) or a network infrastructure.
This type of topology is common in small networks or temporary setups, where devices need to
communicate with each other on-the-fly.

Infrastructure Topology
Infrastructure Topology:
In an infrastructure topology, wireless devices communicate through a central access point (AP)
or a wireless router.
This is a common configuration for Wi-Fi networks. Devices connect to the access point, and the
access point manages the communication between devices and provides a connection to the
wired network.

Mesh Topology:
A wireless mesh topology involves multiple wireless devices that are interconnected, and each
device can relay data for other devices.
Mesh networks are known for their redundancy and self-healing capabilities. If one node fails,
data can find an alternative path through other nodes.

Point-to-Point Topology
In a point-to-point topology, two wireless devices communicate directly with each other.
This is often used for establishing a dedicated link between two locations, such as connecting
two buildings wirelessly.

Point-to-Multipoint Topology:
In a point-to-multipoint topology, one central wireless device (such as an access point)
communicates with multiple remote devices.
This is common in scenarios where a single device serves as a hub for connecting multiple
devices in its vicinity.

Wireless Distribution System (WDS):
WDS is a topology where multiple wireless access points are connected to create an extended
network.
WDS is often used to expand the coverage area of a wireless network by linking multiple access
points wirelessly.

Network Components
Networking components refer to the various hardware and software elements that make up a
computer network, enabling communication and data exchange between devices. These
components work together to facilitate the flow of information within the network. Here are
some key networking components:

Network Devices:
Router: Connects multiple networks together and routes data between them.
Switch: Connects devices within the same network, using MAC addresses to forward data to the
appropriate device.
Hub: A basic networking device that connects multiple devices in a network but operates at the
physical layer without intelligence.

Types of Network Cables and Connectors
1. Unshielded Twisted Pair (UTP) Cable
2. Shielded Twisted Pair (STP) Cable
3. Coaxial Cable
4. Fibre Optics Cable

Unshielded Twisted Pair (UTP) Cable
Twisted pair cabling comes in two varieties: shielded and unshielded.
Unshielded twisted pair (UTP) is the most popular at is generally the best option for
simple networks.

Unshielded Twisted Pair (UTP) Cable

Advantages
Fastest copper-based medium available.
• Less expensive than STP cables, costing less per meter than other types of LAN cabling.
• Have an external diameter of ap roximately .43 cm, making it a smaller cable than STP
cable and easier to work /during installation, as it doesn't fill the wiring cost as fast as other
cables.

Disadvantages
• Susceptible to radio frequency interference (RFI) and electromagnetic interference (EMI)
such as is caused from the microwave.
More prone to electronic noise and interference than other forms of cable

Categories of Unshielded Twisted Pair
(UTP) Cable
Category 5e (Cat5e): Suitable for 1000BASE-T (Gigabit) Ethernet and
lower.
Category 6 (Cat6) Supports higher data transfer rates and is suitable
for 10GBASE-T (10-Gigabit) Ethernet at shorter
distances.
Category 6a (Cat6a) Enhanced version of Cat6, designed to support
10GBASE-T at longer distances.
Category 7 (Cat7) Category 7 (Cat7): Provides improved performance
and shielding, supporting even higher data rates
and better protection against interference.

Shielded Twisted Pair (STP) Cable
a type of copper telephone wiring in which each of the two copper wires that are twisted
together are coated with an insulating coating that functions as a ground for the wires.
The extra covering in shielded twisted pair wiring protects the transmission line from
electromagnetic interference leaking into or out of the cable.

Shielded Twisted Pair (STP) Cable

Advantages
Less susceptible to electrical interference caused by nearby equipment or wires.
Less likely to cause interference themselves.
Fasterspeed in carrying data.

Disadvantages
• Physically larger.
• More expensive than twisted pair wire
• More difficult to connect to a terminating block

Coaxial cable
• Coaxial cabling has a single copper conductor at its center. A plastic layer provides
insulation between the center conductor and a braided metal shield.
The metal shield helps to block any outside interference from fluorescent lights, motors and
other computers.

Types of Coaxial Cables
1. Thick Coaxial
2. Thin Coaxial

Thick coaxial cable
Specification Cable Type Maximum Length
10 Base5 Thick Coaxial 500 meters

Thin coaxial cable
Specification Cable Type Maximum Length
10 Base2 Thin Coaxial 185 meters

Coaxial Cable Connector
• The most common type of connector used with coaxial cables is the Bayone-Neill
Concelman (BNC) connector.
• Different types of adapters are available for BNC connectors, including a T connector,
barrel connector, and terminator.

Coaxial Cables
RG-6: Commonly used for cable television (CATV) and broadband internet.
RG-59: Older standard often used for analog video signals.

Advantages
• They are cheap to make
• Cheap to install
• Easy to modify
• Good bandwith
• Great channel capacity
• noise immunity due to low rate

Disadvantages
Disadvantages of coaxial
• More expensive than twisted pairs
• Not supported for some network standards (eg. token ring)
• Its also very bulky and also has high attenuation so would have the need ;to iplement
repeaters.

Fibre Optic cables
•Consists of a center glass core surrounded by several layers of protective materials.
•It transmits light rather than electronic signals

Advantages
• System Performance .
• Greatly increased bandwidth and capacity.
• Immunity to Electrical Noise
Freedom from short circuit and sparks

• Expensive to install and the equipment is expensive
• Lack of standardization globally and some locally which makes companies hesitant to use
it.
• Cannot carry power like telephone and electrical signals can.

Single-mode Fiber (SMF): Designed for long-distance, high-bandwidth transmissions. Uses a
single light path.
Multimode Fiber (MMF): Suitable for shorter distances. Allows multiple light paths (modes) to
propagate through the fiber.
Fiber optic cables are commonly categorized by their core and cladding diameters, such as 9/125
µm (micrometers) for single-mode and 50/125 µm or 62.5/125 µm for multimode.

Wireless Network
• Utilize radio waves and/or microwaves to maintain communication channels between
computers. Wireless networking is a more modern alternative to wired networking that
relies on copper and fibre optic cabling between network devices.
• Rapidly gaining in popularity for both home and business networking. Wireless
technology continues to improve, and the cost of wireless products continues to decrease.
• Popular wireless local area networking (WLAN) products conform to the 802.11 "Wi-Fi"
standards. The gear a person needs to build wireless networks Includes network adapters
(NICs), Access points and routers

Advantages
• Easy to add stations as there are no cables required.
• Signals can be sent through doors and walls so the stations can be mobile so can move
around.
• There is less need for technical support in setting up due to their simple nature.
• There are no cables to trip over so there are less health and safety issues to consider
share resources like printers. Have shared access to a centralized storage.

Disadvantages
Signals can suffer from other signals
• To access the networks, you have to be within a certain range
• The wireless networks can be quite slow.
• It is easy for hackers to hack or catch the signal

Power over Ethernet (PoE) Cable
Designed to carry electrical power alongside data on Ethernet cabling. Allows devices like IP
cameras and VoIP phones to be powered over the Ethernet cable.
Kbps – Kilobits per second – 100bits
Mbps – Megabits per second –
1000bits
Gbps –Gigabits per seconds 10000

Network Standards
A networking standard is a set of specifications, guidelines, and other characteristics that are
applied to networking components in order to provide interoperability and consistency.
Standards will apply to virtually all parts of a particular technology
Cables
Connectors
Segment lengths
Transmission methods
Signal types

Why do we use standards?
Multiple vendors would result in
 Inconsistencies at best
 Incompatibilities at worst
Without standards, manufacturers could make any claims about their devices
 Standards define the minimum acceptable level of performance
 Still provide room to enhance capabilities Within a particular framework

Standards Organizations
ISO – International Organization for Standardization
IEEE – Institute for Electrical and Electronics Engineers
ANSI – American National Standards Institute
TIA/EIA – Telecommunications Industry Association and Electronics Industry Alliance
IETF – Internet Engineering Taskforce

IEEE Networking Standards
IEEE Networking Standards
IEEE 802.x Standards – family of networking standards that directly apply to computer
networking and are divided into subcategories to address different requirements and
capabilities o 802.2-developed to address the need for a MAC sub-layer type of addressing in
switches and specifies frame rate and transmission speeds
802.3 issued by the IEEE to modify the original Ethernet standard released by XEROX in the
1970s
802.5 issued to address Token Ring architectures
802.11 issued to address Wireless LAN architectures
802.15 - wireless personal area networks
802.16 - WiMAX, a type of wireless MAN

10Base Standards
Standard Ethernet
10Base2 – Thinnet
10Base5 – Thicknet
10BaseT
Fast Ethernet
100 Base T
100 BaseFX – Fibre Cabling
Gigabit Ethernet
1000BaseT
1000BaseFX
10G Ethernet
 10GBase-T – requires Cat6a for up
to 100 meters over twisted pair
 10GBaseSR or SW – Preferred
choice for optical cabling within
buildings over multi-mode fiber
 10GBaseER or EW – use single
mode fibre up to 40km

Mac Addresses
Media Access Control
Unique address permanently embedded by the
manufacturer
A 48-bit hexadecimal address represented as six
pairs of hex numbers separated by hyphens
First three pairs are the manufactuerer ID, and the
last three pairs are the unique identifier
Can be modified due to flash ROM on newer NICs

OSI/RM
Open Systems Interconnection / Reference Model
 A standard framework used to describe networking
communications
 Used by developers to create protocols and applications that
interface with the network
 Not incredibly practical for day-to-day administration but can
be useful as a conceptual model
Consists of seven layers that define network
communications
 Numbered in order from bottom (Layer 1) to top (Layer 7)
 Each layer adds information to the packet
 Network devices operate at a specific layer

Upper Layers
OSI
Applications – application to network services
◦ HTTP
◦ POP/IMAP
◦ SMTP
◦ DNS
◦ TELNET
Presentation – translates the application layer data to an intermediate form that provides security,
encryption, and compression of data.
Session - establishes and controls data communication between applications operating on different
computers.

Lower layers
Transport - divides long communications into smaller packages (fragments), handles error correction,
and acknowledges the receipt of data
◦ Segmentation
◦ Sequencing
◦ Acknowledgements
◦ Checksums
Network - addresses data messages and handles message routing
◦ Protocol addresses
◦ Datagrams
Data link layer - packages bits of data from the physical layer into frames and transfers them from one
computer to another
◦ Physical Addresses
◦ CRC
Physical - transmits bits from one computer to another and regulates the transmission stream over a
medium

Transmission methods
Transmission methods refer to the ways in which data is transferred between devices in a
network. There are several transmission methods, each with its characteristics and use cases.
Guided Transmission Media:
Twisted Pair Cable: Consists of pairs of insulated copper wires twisted together. It's commonly
used for telephone lines and Ethernet networks.
Coaxial Cable: Has a central conductor surrounded by an insulating layer, a metallic shield, and
an outer insulating layer. It's often used for cable television and broadband internet.
Optical Fiber: Uses light signals transmitted through a glass or plastic fiber. It offers high
bandwidth and is widely used for high-speed internet and long-distance communication.

Unguided Transmission Media:
Wireless Communication: Involves the transmission of data without a physical medium.
◦ Radio Waves: Used in technologies like Wi-Fi and Bluetooth.
◦ Microwaves: Common in point-to-point communication over short distances.
◦ Infrared: Used in remote controls and short-range communication.
Multiplexing:
Frequency Division Multiplexing (FDM): Divides the frequency bandwidth into multiple
channels, each carrying a different signal simultaneously (e.g., radio broadcasting).
Time Division Multiplexing (TDM): Divides the transmission time into multiple time slots, and
each device gets its time slot to transmit data (e.g., traditional telephone networks).

Switching:
Circuit Switching: Establishes a dedicated communication path between two devices for the
duration of their conversation (e.g., traditional telephone networks).
Packet Switching: Divides data into packets and sends them independently to their destination,
where they are reassembled (e.g., the Internet).
Modulation:
Amplitude Modulation (AM) and Frequency Modulation (FM): Commonly used in radio
broadcasting.
Phase Shift Keying (PSK) and Quadrature Amplitude Modulation (QAM): Used in digital
communication, including Wi-Fi and cable modems.

Serial and parallel
Serial and parallel are two different methods of transmitting data between devices. They refer to the
way in which bits of data are sent over communication channels.
Serial Transmission:
In serial transmission, data is sent one bit at a time over a single communication channel. The bits are
sent sequentially, one after the other.
Method: A single data line is used for transmission, and the bits are sent in a continuous stream.
Advantages:
◦ Requires fewer physical wires, making it simpler to implement.
◦ Suitable for long-distance communication as it is less prone to signal degradation.
Disadvantages:
◦ Slower compared to parallel transmission for large amounts of data.
◦ May require additional synchronization mechanisms.

Parallel Transmission
In parallel transmission, multiple bits are sent simultaneously over multiple communication
channels. Each bit has its own dedicated wire or channel.
Method: Each bit of the data word is transmitted at the same time but on a separate wire.
Advantages:
◦ Faster transmission of data compared to serial, especially for large amounts of data.
◦ Well-suited for short-distance communication within a single device or between closely located devices.
Disadvantages:
◦ Requires a larger number of physical wires, which can be complex and costly.
◦ Susceptible to timing issues, as bits must arrive at the destination simultaneously.

Comparison
Data Rate: Serial transmission is generally slower than parallel transmission for transmitting a large
amount of data. Parallel transmission allows for higher data rates since multiple bits are transmitted
simultaneously.
Distance: Serial transmission is more suitable for long-distance communication, as it requires fewer
wires and is less susceptible to signal degradation. Parallel transmission is often used for short-
distance communication within a device or between closely located devices.
Complexity: Serial transmission is simpler to implement because it requires fewer wires. Parallel
transmission is more complex due to the need for multiple wires and the requirement for precise
timing.
Examples:
◦ Serial Transmission: USB, RS-232, Ethernet (although it often uses multiple pairs of wires for parallel
communication within each pair).
◦ Parallel Transmission: Older printer cables (e.g., Centronics parallel port), parallel ATA (PATA) for connecting
hard drives (though it is becoming less common).

Baseband and broadband are terms used to describe different types of signaling and communication
technologies. They refer to the way in which signals, particularly in the context of networking and
telecommunications, are transmitted over a communication medium.
Baseband:
Baseband refers to a type of communication in which digital signals are sent over a single, dedicated
communication channel.
Characteristics:
◦ The entire bandwidth of the medium is used for a single digital signal.
◦ Typically used in short-distance communication systems, such as within a computer or between devices in
close proximity.
◦ Ethernet LANs (Local Area Networks) often use baseband communication.
Example: In a baseband transmission system, the entire capacity of the cable is dedicated to one
channel, and the signal is typically digital (e.g., Ethernet cables transmitting data between computers
in a local network).

Broadband
Broadband refers to a type of communication in which multiple signals, often of different
frequencies, are transmitted simultaneously over a shared communication medium.
Characteristics:
◦ The available bandwidth is divided into multiple channels, each carrying a different signal.
◦ Suitable for transmitting multiple signals, including voice, video, and data, simultaneously.
◦ Commonly used for internet access, cable television, and other wide-area communication systems.
Example: Cable modems and Digital Subscriber Line (DSL) are examples of broadband
technologies. They allow the simultaneous transmission of data, voice, and video over the same
communication medium.

Multiplexing
Multiplexing is a technique used in networking to combine multiple signals or data streams into
a single transmission medium. This helps optimize the use of network resources and improve
efficiency.
Time Division Multiplexing (TDM):
In TDM, multiple signals are transmitted over the same communication channel in a timed
sequence.
Each signal is assigned a specific time slot, and they take turns using the channel.
TDM is commonly used in technologies like T1 and E1 lines.

Frequency Division Multiplexing (FDM):
◦ FDM involves dividing the available bandwidth into multiple frequency bands.
◦ Each signal is assigned a specific frequency range, and they can coexist without interfering with each
other.
◦ FDM is often used in technologies like traditional analog television broadcasting.
Wavelength Division Multiplexing (WDM):
◦ Similar to FDM but used in optical communication.
◦ WDM divides the optical spectrum into different wavelengths (colors of light) and assigns each signal to
a specific wavelength.
◦ This technique is used in fiber optic communications.

Code Division Multiplexing (CDM):
In CDM, each signal is assigned a unique code.
All signals can then be transmitted simultaneously over the same frequency band.
This is commonly used in CDMA (Code Division Multiple Access) technologies in mobile
communications.

Security concepts
Firewalls:
Firewalls are devices or software that monitor and control incoming and outgoing network
traffic based on predetermined security rules.
They act as a barrier between a trusted internal network and untrusted external networks, such
as the internet.

Intrusion Detection Systems (IDS) and Intrusion Prevention Systems (IPS):
IDS monitors network or system activities for malicious activities or security policy violations.
IPS goes a step further by actively preventing or blocking identified threats.

Vrtual Private Network (VPN):
VPNs provide a secure, encrypted connection over the internet, allowing users to access a
private network from a remote location.
They are commonly used to ensure secure communication over untrusted networks.

Authentication:
Authentication is the process of verifying the identity of a user, device, or system.
Common methods include passwords, biometrics, and multi-factor authentication (MFA).
Authorization:
Authorization determines what actions a user, device, or system is allowed to perform after
successful authentication.
It involves granting appropriate permissions and access levels.

Security Protocols:
◦ Security protocols are standardized sets of rules for ensuring secure communication.
◦ Examples include HTTPS (HTTP Secure), SSL/TLS (Secure Sockets Layer/Transport Layer Security), and
IPsec (Internet Protocol Security).
Network Access Control (NAC):
◦ NAC is a security solution that enforces policies to control which devices can access a network and
under what conditions.
◦ It helps prevent unauthorized access and ensures compliance with security policies.
Security Threats:
◦ Understand various security threats, such as malware (viruses, worms, trojans), phishing, ransomware,
and denial-of-service (DoS) attacks.

Network troubleshooting
Network troubleshooting involves a systematic approach to identify, isolate, and resolve issues
affecting the functionality and performance of a network.

Identify the Problem:
Start by gathering information from the user or system experiencing issues. Understand the
symptoms, when the problem started, and any recent changes to the network.
Clearly define the problem to narrow down potential causes.

Establish a Theory of Probable Cause:
Based on the information gathered, formulate a hypothesis or theory about the likely cause of
the issue. Consider both the symptoms reported and your understanding of the network's
architecture.

Test the Theory to Determine the Cause:
Perform diagnostic tests to validate or invalidate the theory of probable cause. Use network
troubleshooting tools, logs, and monitoring systems to gather data.
Start with the simplest and most likely causes before moving on to more complex scenarios.

Establish a Plan of Action to Resolve the Problem:
Once the cause is identified, develop a plan of action to address the issue. Consider the
potential impact of the proposed solutions on the network and users.
Prioritize tasks based on criticality and potential impact.

Implement the Solution:
Apply the changes or fixes according to the plan of action. This may involve reconfiguring
network devices, applying patches, updating software, or making other adjustments.

Verify Full System Functionality:
Test the network to confirm that the implemented solution resolves the issue. Verify that the
symptoms reported by users no longer exist.
Monitor the network for any unexpected side effects of the changes.

Document the Solution:
Document the steps taken to identify and resolve the issue. This documentation serves as a
record for future troubleshooting efforts and helps in knowledge transfer.

Implement Preventive Measures:
Consider implementing preventive measures to avoid similar issues in the future. This may
involve updating policies, improving monitoring, or enhancing network security.
Evaluate the overall network architecture for potential improvements.

Communicate with Stakeholders:
Communicate with users, management, and other relevant stakeholders to inform them of the
resolution. Provide information about the cause of the issue, the steps taken to resolve it, and
any preventive measures implemented.

Create a Baseline:
Establish a baseline of normal network behavior using monitoring tools. This baseline helps in
quickly identifying deviations and potential issues in the future.
Regularly update and review the baseline to adapt to changes in the network environment.

Follow Up:
◦ After resolving the issue, follow up with users and stakeholders to ensure that the solution meets their
expectations.
◦ Review the entire troubleshooting process to identify any areas for improvement.
Adopting a structured and systematic troubleshooting methodology helps network

TCP/IP Overview
TCP/IP (Transmission Control Protocol/Internet Protocol) is a suite of communication protocols
that form the backbone of the internet and many private networks. It provides a standardized
framework for transmitting data across diverse networks, ensuring reliable and efficient
communication between devices.

History
Origins: Developed by the U.S. Department of Defense in the 1970s as part of the ARPANET
project, TCP/IP became the standard for interconnecting heterogeneous networks.
Evolution: As the internet expanded, TCP/IP played a pivotal role in unifying various networks,
leading to its widespread adoption as the de facto standard for internet communication.
Standardization: The protocol suite was formalized into a set of standards by the Internet
Engineering Task Force (IETF) and the International Organization for Standardization (ISO).

Benefits:
Interoperability:
◦ Description: TCP/IP enables seamless communication between devices, regardless of the underlying
hardware and software.
◦ Benefit: This interoperability has been instrumental in the global expansion of the internet.
Scalability:
◦ Description: TCP/IP accommodates networks of various sizes, from small local networks to the vast,
interconnected global internet.
◦ Benefit: Its scalability has allowed for the growth of the internet and the addition of countless devices.
Open Standards:
◦ Description: TCP/IP protocols are open and standardized, encouraging collaboration and innovation.
◦ Benefit: This openness has fostered a vibrant ecosystem of technologies and applications.

Robustness:
◦ Description: TCP/IP includes error-checking mechanisms and built-in redundancy, ensuring the robust and reliable
transmission of data.
◦ Benefit: This robustness contributes to the stability of internet communications.
Flexibility:
◦ Description: TCP/IP supports different types of networks, including wired and wireless, making it adaptable to evolving
technologies.
◦ Benefit: Its flexibility allows for the integration of new devices and technologies.
Global Connectivity:
◦ Description: TCP/IP facilitates global connectivity by providing a common language for devices to communicate over the
internet.
◦ Benefit: This global reach has transformed the way information is accessed, shared, and disseminated worldwide.
Standardization of Communication:
◦ Description: TCP/IP standardizes the format and rules for data transmission, ensuring a consistent method of
communication.
◦ Benefit: Standardization simplifies development and ensures compatibility between different devices and platforms.

Layers of the TCP/IP Model:
Application Layer:
◦ Interface between software applications and the network.
◦ Protocols include HTTP, HTTPS, FTP, SMTP.
Transport Layer:
◦ Manages end-to-end communication.
◦ Protocols include TCP (reliable, connection-oriented) and UDP (unreliable, connectionless).
Internet Layer:
◦ Handles logical addressing and routing.
◦ Protocols include IP (IPv4 and IPv6) and ICMP.
Link Layer:
◦ Deals with physical addressing and framing.
◦ Protocols include ARP, Ethernet, PPP.

Core protocols
Transport
TCP (Transmission Control Protocol):
◦ Connection-oriented protocol that ensures reliable and ordered delivery of data.
◦ Commonly used for applications like HTTP, SMTP, and FTP.
UDP (User Datagram Protocol):
◦ Connectionless protocol that provides faster, but less reliable, data delivery.
◦ Commonly used for real-time applications like VoIP and streaming.

Internet
IP (Internet Protocol):
◦ Provides logical addressing for devices on the network.
◦ IPv4 and IPv6 are the two major versions.
ICMP (Internet Control Message Protocol):
◦ Used for network diagnostics and error reporting.
◦ Includes tools like Ping and Traceroute.
ARP (Address Resolution Protocol):
◦ Maps IP addresses to MAC addresses in a local network.
DHCP (Dynamic Host Configuration Protocol):
◦ Assigns IP addresses dynamically to devices on a network.
DNS (Domain Name System):
◦ Resolves human-readable domain names to IP addresses.

Transport Protocols
There are many functions performed at the transport layer in TCP/IP by two specific transport
layer protocols
◦ Transmission Control Protocol
◦ User Datagram Protocol
Functions
◦ Divide larger packets into smaller sections to ready for transport (fragmentation)
◦ Assign sequence numbers to packets for correct assembly at the destination
◦ Identify application layer protocols using port numbers and sockets

Transmission Control Protocol (TCP)
Connection-Oriented:
◦ TCP is a connection-oriented protocol, meaning it establishes a reliable connection before data
exchange.
◦ It ensures the ordered and error-checked delivery of data.
Reliability:
◦ TCP guarantees the delivery of data without loss or duplication.
◦ It uses mechanisms such as acknowledgment and retransmission to ensure reliable communication.
Flow Control:
◦ TCP implements flow control mechanisms to manage the rate of data transmission, preventing
congestion and ensuring optimal performance.

Ordered Delivery:
◦ TCP ensures that data is delivered in the same order it was sent, crucial for applications that require
sequential data delivery.
Connection Establishment and Termination:
◦ TCP follows a three-way handshake process to establish a connection and uses a four-way handshake
for termination.
Applications:
◦ Ideal for applications where data integrity and accuracy are critical, such as file transfer (FTP), email
(SMTP), and web browsing (HTTP).

User Datagram Protocol (UDP)
Connectionless:
◦ UDP is a connectionless protocol, offering a simpler, lightweight alternative to TCP.
◦ It does not establish a connection before data transmission.
Best Effort Delivery:
◦ UDP does not guarantee the delivery of data, and it does not implement flow control or error
correction.
◦ It is considered a "best effort" protocol, suitable for applications where occasional data loss is
acceptable.
Low Overhead:
◦ UDP has lower overhead compared to TCP since it lacks the extensive error-checking and flow control
mechanisms.
◦ This results in faster data transmission but with less reliability.

Broadcast and Multicast Support:
◦ UDP supports broadcast and multicast communication, making it suitable for scenarios where data
needs to be sent to multiple recipients.
Applications:
◦ Commonly used for real-time applications, such as VoIP (Voice over Internet Protocol), video streaming,
and online gaming.

Sockets
A socket is a software endpoint that establishes communication between processes or
applications running on different devices in a network. It provides a standardized interface for
programs to send and receive data over a network, allowing communication between
applications on the same or different devices

Endpoint of Communication:
◦ A socket serves as an endpoint for communication, allowing data to be sent and received between
processes or applications.
Network Protocol:
◦ Sockets are associated with a specific network protocol, such as TCP (Transmission Control Protocol) or
UDP (User Datagram Protocol). The choice of protocol determines the characteristics of the
communication, such as reliability and ordering.
IP Address and Port Number:
◦ A socket is identified by a combination of an IP address and a port number. The IP address specifies the
device's location in the network, and the port number identifies a specific process or application on that
device.

Socket Types:
◦ Sockets can be classified into various types, including:
◦ Stream Sockets (TCP): Provide a reliable, connection-oriented communication with data streaming in a continuous flow.
◦ Datagram Sockets (UDP): Offer connectionless communication with discrete packets of data, suitable for scenarios where
occasional loss of data is acceptable.
Socket API (Application Programming Interface):
◦ Programming languages provide a socket API that allows developers to create, configure, and manage
sockets in their applications. Common socket APIs include the Berkeley Sockets API and Windows
Sockets (Winsock) API.
Server and Client Sockets:
◦ In a client-server model, a server socket waits for incoming connection requests, while client sockets
initiate connections to servers. Once a connection is established, both server and client sockets can
send and receive data.

Connection Lifecycle:
◦ The lifecycle of a socket typically involves creating a socket, binding it to a specific IP address and port,
listening for incoming connections (server socket), establishing a connection (client socket), and finally,
sending and receiving data.
Socket Communication Process:
◦ Socket communication involves establishing a connection, exchanging data, and eventually closing the
connection when the communication is complete.
Sockets play a crucial role in various network applications, including web browsers, email clients,
and online games. They provide a flexible and efficient means for applications to communicate
over a network, enabling the development of a wide range of distributed systems.

Internet Layer
The Internet layer, also known as the Network layer, is a crucial component of the TCP/IP
protocol suite and is responsible for logical addressing, routing, and facilitating communication
between devices across different networks. In the TCP/IP model, the Internet layer operates
between the Link layer and the Transport layer.

Key Characteristics of the Internet Layer:
Logical Addressing:
◦ The Internet layer uses logical addressing to uniquely identify devices on a network. The most common
example of Internet layer addressing is the IP (Internet Protocol) address.
IP Addressing:
◦ Devices on the Internet layer are assigned IP addresses, which can be IPv4 (32-bit) or IPv6 (128-bit). IP
addresses play a critical role in routing packets to their intended destinations.
Routing:
◦ The primary responsibility of the Internet layer is to facilitate the routing of data packets between
devices on different networks. Routers at the Internet layer use logical addressing information to
forward packets toward their destination.

Packet Encapsulation:
◦ Data from the Transport layer is encapsulated into packets at the Internet layer. Each packet contains the
source and destination IP addresses, allowing routers to make routing decisions.
Internet Control Message Protocol (ICMP):
◦ ICMP is a companion protocol to IP and operates at the Internet layer. It is used for network diagnostics, error
reporting, and generating error messages, including tools like Ping and Traceroute.
Fragmentation and Reassembly:
◦ The Internet layer can fragment large packets into smaller fragments for transmission across networks with
different Maximum Transmission Unit (MTU) sizes. At the destination, the fragments are reassembled into the
original packet.
IPv4 and IPv6:
◦ IPv4 has been the dominant version of the Internet layer protocol, but due to the exhaustion of IPv4
addresses, IPv6 has been introduced. IPv6 provides a significantly larger address space to accommodate the
growing number of devices connected to the internet.

Functions of the Internet Layer:
Logical Addressing:
◦ Assigning logical addresses (IP addresses) to devices for identification.
Routing:
◦ Determining the optimal path for data packets to reach their destination across interconnected
networks.
Packet Forwarding:
◦ Forwarding data packets based on logical addressing information.
Fragmentation and Reassembly:
◦ Breaking down large packets into smaller fragments for transmission and reassembling them at the
destination.

Error Handling:
◦ Handling errors and generating error messages using ICMP.
IPv4 to IPv6 Transition:
◦ Facilitating the transition from IPv4 to IPv6 to address the limitations of IPv4 address exhaustion.
In summary, the Internet layer is a critical component of the TCP/IP protocol suite, providing
logical addressing, routing, and communication across networks. Its protocols, primarily IP,
enable the global connectivity that defines the internet.

Core protocols of the Internet layer
The core protocols of the Internet layer in the TCP/IP protocol suite include the Internet Protocol
(IP) itself, along with supporting protocols that play crucial roles in facilitating communication
and addressing. The key protocols at the Internet layer are:
Internet Protocol (IP):
◦ IPv4 (Internet Protocol version 4): The most widely used version of IP, which uses 32-bit addresses.
◦ IPv6 (Internet Protocol version 6): Developed to address the limitations of IPv4, IPv6 uses 128-bit
addresses, providing a significantly larger address space.
Internet Control Message Protocol (ICMP):
◦ Function: ICMP operates alongside IP and is used for diagnostic and error-reporting purposes.
◦ Common Tools: ICMP is utilized by tools such as Ping (Packet Internet Groper) and Traceroute for
network troubleshooting.

Internet Group Management Protocol (IGMP):
◦ Function: Facilitates the management of multicast group memberships on a network.
◦ Use Case: Particularly important for supporting multicast communication, where a single packet is sent to
multiple recipients.
Address Resolution Protocol (ARP):
◦ Function: Maps an IP address to its corresponding physical (MAC) address on a local network.
◦ Use Case: Essential for local communication within a subnet.
Reverse Address Resolution Protocol (RARP):
◦ Function: Performs the reverse of ARP, mapping a MAC address to its corresponding IP address.
◦ Use Case: Used in some legacy scenarios for diskless workstations to obtain an IP address.
Internet Protocol Security (IPsec):
◦ Function: Provides security services at the Internet layer, including authentication and encryption.
◦ Use Case: Ensures secure communication between devices on an IP network.

These protocols collectively form the core set of Internet layer protocols, allowing for logical
addressing, routing, error reporting, multicast support, and security. The Internet layer is
responsible for the end-to-end communication across interconnected networks, making these
protocols foundational for global connectivity. It's important to note that while IP is a required
component of the Internet layer, other protocols like ICMP, IGMP, and ARP enhance its
functionality and support specific networking requirements.

Well known networking ports
Networking ports are specific endpoints through which data is transmitted and received on a computer network.
FTP (File Transfer Protocol):
◦ Port 21 (Control)
◦ Port 20 (Data)
SSH (Secure Shell):
◦ Port 22
Telnet:
◦ Port 23
SMTP (Simple Mail Transfer Protocol):
◦ Port 25
DNS (Domain Name System):
◦ Port 53 (TCP and UDP)
HTTP (Hypertext Transfer Protocol):
◦ Port 80

SNMP (Simple Network Management Protocol):
◦ Port 161 (UDP)
LDAP (Lightweight Directory Access Protocol):
◦ Port 389
HTTPS (LDAP over TLS/SSL):
◦ Port 636
SMB (Server Message Block):
◦ Port 445
RDP (Remote Desktop Protocol):
◦ Port 3389
MySQL Database:
◦ Port 3306

HTTP Proxy:
◦ Port 8080
NTP (Network Time Protocol):
◦ Port 123 (UDP)
DHCP (Dynamic Host Configuration Protocol):
◦ Port 67 (UDP) - DHCP Server
◦ Port 68 (UDP) - DHCP Client
RADIUS (Remote Authentication Dial-In User Service):
◦ Port 1812 (UDP)
VPN (Virtual Private Network):
◦ PPTP: Port 1723
◦ L2TP: Port 1701
◦ IPsec: Port 500

HTTPS (Hypertext Transfer Protocol Secure):
◦ Port 443
POP3 (Post Office Protocol version 3):
◦ Port 110
IMAP (Internet Message Access Protocol):
◦ Port 143

IP addresses
The current version of TCP/IP is known as IPv4 and specifies a particular address structure using
32-bit binary addresses
IP addresses are required for every node on a TCP/IP network in order for network
communication to occur
IP addresses are 32-bit binary numbers written in decimal form and grouped into octets (8 bits)
in the format w.x.y.z where part of the address belongs to the network segment and the other
belongs to the host.
NETWORK ID HOST ID

Subnet Mask
Subnet Masks
The subnet mask is another 32-bit binary number that is used by routers and hosts to determine
the network and host portions of the address
The mask is continuous binary 1's which mark the network portion of the IPv4 address - when
the 1's stop the host portion begins.
192.168.1.200 172.16.18.128
255.255.255.0 255.255.0.0
192.168.1.0 172.16.0.0

IPv4 Address Rules
Certain Rules apply to IP Addresses and Subnet Masks o Acceptable values in IP addresses range
from 0-255 in each octet
◦ 172.16.0.254 VALID
◦ 172.256.244.100 INVALID
Host portion of the address cannot be all 1's or all O's
◦ 172.16.255.255 - INVALID
◦ 10.0.0.1 VALID
◦ 10.0.0.0 - INVALID
Host and Network combination must be unique

Default Gateway
Each node will require three components in order to access local and remote networks and
computers
◦ IP address
◦ Subnet Mask
◦ Default Gateway
The default gateway is typically the address of the router interface and allows access to remote
network segments

Address Catergories
Public IP Addresses:
Definition: Public IP addresses are assigned by the Internet Assigned Numbers Authority (IANA)
and are globally unique. These addresses are routable on the public Internet.
Use: Public IP addresses are used for communication between devices over the Internet. Web
servers, email servers, and other devices accessible from the Internet have public IP addresses.
Examples: 8.8.8.8 (Google's public DNS), 208.67.222.222 (OpenDNS), etc.

Private IP Addresses:
Definition: Private IP addresses are reserved for use within private networks and are not
routable on the global Internet. These addresses are defined in RFC 1918.
Use: Private IP addresses are used for internal communication within a private network, such as
within a home or business network. Devices within the same private network can communicate
with each other using these addresses.
Examples:
◦ Class A: 10.0.0.0 to 10.255.255.255 (e.g., 10.0.0.1)
◦ Class B: 172.16.0.0 to 172.31.255.255 (e.g., 172.16.0.1)
◦ Class C: 192.168.0.0 to 192.168.255.255 (e.g., 192.168.0.1)
Note: Network Address Translation (NAT) is often used to map private IP addresses to a single
public IP address when these devices need to communicate with the Internet.

Introduction to IPv6 Addresses:
IPv6, or Internet Protocol version 6, is the most recent version of the Internet Protocol, designed
to succeed IPv4. The transition to IPv6 became necessary due to the exhaustion of available IPv4
addresses. IPv6 offers a significantly larger address space, improved security features, and more
efficient routing. Here's an introduction to IPv6 addresses:

IPv6 Address Format:
Length:
IPv6 addresses are 128 bits long, compared to the 32 bits of IPv4 addresses.
Hexadecimal Representation:
IPv6 addresses are expressed in hexadecimal notation, providing a larger pool of available
characters. An example IPv6 address looks like: 2001:0db8:85a3:0000:0000:8a2e:0370:7334.
Colon-Hex Notation:
To simplify IPv6 addresses, groups of consecutive zeros within an address can be omitted, and a
double colon (::) is used to represent them. For instance, 2001:0db8::0370:7334.

Address Types:
Global Unicast Addresses:
Equivalent to public IPv4 addresses, used for communication over the Internet.
Link-Local Addresses:
Used for communication within a single subnet and are not routable outside that subnet.
Unique Local Addresses (ULA):
Similar to IPv4 private addresses, intended for local communication within an organization.

Multicast Addresses:
◦ Used for one-to-many communication, similar to IPv4 multicast addresses.
Anycast Addresses:
◦ Assigned to multiple devices, but the data is sent to the nearest one in terms of routing topology.

Classful IP Addressing:
Fixed Classes:
◦ In the original design of IPv4, addresses were divided into fixed classes—Class A, Class B, and Class C.
◦ Each class had a predefined range of network and host bits. For example, Class A had a default of 8
network bits and 24 host bits.
Limited Flexibility:
◦ Classful addressing offered limited flexibility in terms of addressing. Each class came with a fixed
number of available host addresses, regardless of the actual number of hosts on a network.
Wasteful Allocation:
◦ It often led to inefficient use of IP address space because, for example, a Class C address block (256
addresses) was allocated even if a network needed only a few addresses.

Classless IP Addressing (CIDR):
Variable-Length Subnet Mask (VLSM):
◦ Classless Inter-Domain Routing (CIDR) introduced the concept of Variable-Length Subnet Masking (VLSM). This
allows subnetting at any bit boundary, providing more flexibility in allocating addresses.
Efficient Use of Address Space:
◦ CIDR allows network administrators to allocate address space based on the actual needs of their networks,
reducing address space wastage.
Prefix Notation:
◦ CIDR uses prefix notation, where the number after the slash (/) indicates the length of the network prefix. For
example, 192.168.1.0/24 signifies a network with a 24-bit prefix (leaving 8 bits for host addresses).
Classless Routing:
With CIDR, routers do not rely on the fixed class boundaries. Instead, routing tables can contain
entries with varying prefix lengths, making routing more efficient.

Flexibility Comparison:
Classful:
◦ Limited flexibility due to fixed class boundaries.
◦ Wasteful allocation of address space.
◦ No support for subnetting within a class.
Classless (CIDR):
◦ Offers greater flexibility with variable-length subnetting.
◦ Enables efficient use of address space.
◦ Supports hierarchical addressing and aggregation for more efficient routing.

Classful IP Addressing
Classful IP addressing was the original method for allocating IP addresses on the Internet. It
divided the available IPv4 address space into fixed classes, each serving a specific purpose based
on the size of the network it was intended for. Classful addressing, however, has been largely
replaced by Classless Inter-Domain Routing (CIDR), which allows for more flexible allocation of IP
addresses. Here's an overview of classful IP addressing:

Classes of IP Addresses:
Class A:
Range: 1.0.0.0 to 126.255.255.255
Leading Bits: 0
Network/Host Bits: N.H.H.H
Default Subnet Mask: 255.0.0.0
Originally designed for large networks.

Class B:
Range: 128.0.0.0 to 191.255.255.255
Leading Bits: 10
Network/Host Bits: N.N.H.H
Intended for medium-sized networks.

Class C:
Range: 192.0.0.0 to 223.255.255.255
Leading Bits: 110
Network/Host Bits: N.N.N.H
Designed for small networks.

Class D (Multicast):
Range: 224.0.0.0 to 239.255.255.255
Leading Bits: 1110
Reserved for multicast groups.

Class E (Experimental):
Range: 240.0.0.0 to 255.255.255.255
Leading Bits: 1111
Reserved for experimental purposes.

Characteristics of Classful Addressing
Fixed Class Boundaries:
◦ IP addresses were divided into fixed classes, and each class had a predefined range of network and host
bits.
Inefficient Address Allocation:
◦ Often led to inefficient use of IP address space, especially when a network didn't need the full range of
addresses provided by a class.
No Support for Subnetting:
◦ Classful addressing did not originally support subnetting, which caused challenges in managing address
space.
Address Space Wastage:
Allocated large blocks of addresses to organizations, even if they didn't require that many,
resulting in significant wastage of address space.

IPv6 Advantages:
Larger Address Space:
◦ IPv6 provides an enormous address space, allowing for the accommodation of the growing number of
devices connected to the Internet.
Efficient Routing:
◦ Simplifies routing tables and improves the efficiency of Internet routing.
Enhanced Security:
◦ Includes features such as IPsec (Internet Protocol Security) as a fundamental part of the protocol,
enhancing end-to-end security.

Simplified Configuration:
◦ Simplifies network configuration through Stateless Address Autoconfiguration (SLAAC) and DHCPv6.
Elimination of NAT (Network Address Translation):
◦ With the vast address space, the need for NAT is reduced, simplifying end-to-end communication.

Virtual IP
When a public IP address is substituted for the actual private IP address that has been assigned
to the network interface of the device, the public IP address becomes an example of what is
called a virtual IP address. This means it doesn’t correspond to an actual physical network
interface.

Network devices
Network devices are hardware components that play specific roles in the communication and
connectivity of devices within a network. These devices work together to facilitate the
transmission of data across networks.

1. Router:
Function: Connects different networks and directs data between them based on IP addresses.
Key Features:
◦ Manages traffic between devices on different networks.
◦ Assigns local IP addresses to devices within a network.

2. Switch:
Function: Connects devices within a local network, using MAC addresses to forward data to the
appropriate device.
Key Features:
◦ Operates at the data link layer (Layer 2) of the OSI model.
◦ Efficiently manages network traffic.

3. Hub:
Function: Connects multiple devices within a local network, but it operates at the physical layer
and lacks the intelligence of a switch.
Key Features:
◦ Broadcasts data to all connected devices.
◦ Not commonly used in modern networks due to limitations.

4. Firewall:
Function: Monitors and controls incoming and outgoing network traffic based on predetermined
security rules.
Key Features:
◦ Acts as a barrier between a secure internal network and external untrusted networks.
◦ Prevents unauthorized access and protects against cyber threats.

5. Access Point (AP):
Function: Enables wireless connectivity for devices, forming the basis of Wi-Fi networks.
Key Features:
◦ Allows devices to connect to a wired network wirelessly.
◦ Manages the communication between wireless devices.

6. Bridge:
Function: Connects and filters traffic between two network segments at the data link layer.
Key Features:
◦ Reduces collision domains in Ethernet networks.
◦ Segments a larger network into smaller, more manageable parts.

7. Modem:
Function: Converts digital signals from a computer or network into analog signals suitable for
transmission over telephone or cable lines.
Key Features:
◦ Commonly used for broadband Internet access.

8. Gateway:
Function: Connects networks with different communication protocols.
Key Features:
◦ Translates data between different network architectures.
◦ Enables communication between networks with different protocols.

9. Load Balancer:
Function: Distributes incoming network traffic across multiple servers to ensure no single server
is overwhelmed.
Key Features:
◦ Improves the performance, availability, and reliability of applications.

10. Proxy Server:
Function: Acts as an intermediary between a user's device and the internet to provide security,
administrative control, and caching services.
Key Features:
◦ Enhances security by filtering content and preventing direct access to internal network resources.

Device Capabilities
The OSI/RM is far more than just a conceptual model and can assist us in understanding network
communications as well as the functionality of particular network devices
Network devices will be associated with a particular layer, and this will assume certain
capabilities
◦ Layer 1 devices - lack forwarding intelligence, simply deal with physical signals
◦ Layer 2 devices - capable of selective forwarding based on MAC addresses
◦ Layer 3 devices - capable of more advanced forwarding based on protocol addresses

OSI/RM Layers and Devices
Application
Presentation
Session
Transport
Network Router/Layer 3 Switch
Data Link Layer 2 Switch/Bridges/Switching Hubs
Physical Hubs / Repeaters

Physical Devices
Devices that operate at the physical layer are simple devices that lack the ability to intelligently
forward data
Layer 1 Devices
◦ Do not provide network segmentation of any kind
◦ Used to connect systems together in simple networks
◦ Used to extend the range of a signal past the limits of the particular architecture
◦ Most common layer 1 devices are repeaters, hubs, and network interface cards (NIC)

Network Interface Cards
The NIC is used by clients in both wired and wireless networks to connect to network devices
◦ Integrated in motherboard or installed via adapter card
◦ Embedded with a MAC address for communication purposes
◦ Must be matched to media type and network architecture
◦ May transmit in half or full duplex

Repeaters
One of the most basic internetworking devices that boosts the electronic signal from one
network cable segment or wireless LAN and passes it to another
◦ Commonly used to extend the maximum cable length of devices based on the specific media being used
◦ Always use to connect similar media

Types of Repeaters
Amplifier repeaters amplify all incoming signals
Signal-regenerating repeaters (intelligent) read and create an exact duplicate of the original
signal eliminating noise
Wireless
Ethernet
Fiber

Hubs
◦ The original device used to connect multiple computers in the Ethernet star topology
◦ Can connect devices that use a BNC or RJ-45 connector
◦ Very inexpensive and useful for small networks
◦ Easy to configure because they do not intelligently forward packets, instead broadcasting packets out to
all interfaces.
◦ Passive hubs do not extend the range of the signal, whereas active hubs repair weak signals by
regenerating the original signal
◦ The latest hubs can provide additional capabilities

Data Link Filtering
Based on the functionality of the Data Link layer in the OSI/RM, the devices that operate at layer
2 will provide filtering based on hardware addresses (MAC)
Layer 2 Devices create separate collision domains
◦ Ethernet uses a contention-based access method
◦ All nodes are fighting for use of the same bandwidth
◦ Large collision domains are not efficient due to increased collisions
◦ Bridges and switches create separate collision domains on each interface
◦ Packets are only forwarded across an interface if the destination node resides on that network segment
◦ DO NOT provide segmentation to create additional broadcast domains!

Network Bridges
Bridges are internetworking devices that connect to different LANS and make them appear to be
one, or segments a larger LAN into two smaller pieces
◦ Bridges are able to filter messages and only forward messages from one segment to another when
required, using hardware addresses
◦ Transparent to higher-level protocols
◦ Can filter traffic based on addresses
◦ Uncommon in modern networks

Switches
Switches sometimes referred to as a data switch or layer-2 switch, is generally a more modern
term for a multi-port bridge that operates at the data link layer
◦ Basically function as a bridge does, forwarding traffic based on the MAC address at the data link layer
◦ Isolates conversations to create multiple collision domains
◦ Network broadcasts are sent out to all ports
◦ Provide additional filtering techniques to optimize performance
Virtual Switches - software switches providing similar functionality, but used with virtualized
systems communicating over virtual network connections

Switch Category
Unmanaged
◦ Does not support any configuration interfaces or options
◦ Plug and play computers to the switch
◦ Found in home, SOHO, or small business networks
Managed
◦ Support configuration management using various interfaces
◦ Console port, HTTPS, Telnet, SNMP, etc.
◦ Increased functionality using switch protocols
◦ Increased security through authentication
◦ Support for VLAN
Web smart
◦ Hybrid between the two, usually implemented in order to increase capabilities but minimize costs

Switch Characteristics
Port mirroring - duplicates all traffic on a single port to another port and is useful for diagnostics
and traffic monitoring
Channel bonding – increasing throughput by using multiple NICS bound to a single MAC address
◦ Link Aggregation Control Protocol (LACP)
◦ A.K.A "port bonding"

Power over Ethernet
Power over Ethernet (PoE and PoE+)
◦ 802.3af (15.4 W DC per system)
◦ 802.3at (25.5 W DC per system)
◦ Standardized systems that pass power along with data using Ethernet cabling which provides long cable
lengths, unlike other standards

Virtual Capabilities
Trunking combining multiple network connections to increase bandwidth and reliability
◦ Link aggregation
◦ Port teaming
◦ NIC bonding
Virtual LAN (VLAN) - the advanced filtering techniques used by most modern switches that allow
computers connected to separate segments to appear and behave as if they are on the same
segment

Virtual LAN
Modifying the network does not require physical changes
VLANs use configurable managed switches to perform routing and switching, and configuration
is done logically using software
Port-based groupings identify VLAN based on the physical port a machine is connected to
Address-based groupings allow addressing to define the VLAN so that packets are forwarded
only to the appropriate VLAN
Protocol-based groupings allow the switch to examine the access protocol (layer 3 switching)
Subnet-based groupings - allow for switches to identify the appropriate subnet and forward the
packet accordingly on TCP/IP networks (layer 3 switching)

Initial Switch Configuration
There are many configuration options for managed switches, all of which will not be the same
for every switch model
◦ Initial Configuration
◦ Define a default gateway and management IP address
◦ Set the time
◦ Enable neighbor discovery
◦ LLDP
◦ CDP
◦ Configure Logging
◦ Configure SNMP communities

Interface Configuration
Configuring interfaces requires various settings dependent on the scenario
Speed and duplexing settings to ensure efficiency
VLAN settings
◦ VLAN ID
◦ VLAN tags
Port bonding
Port mirroring (local or remote)

Introduction to STP
In larger complex network infrastructures, switching protocols will be used to ensure the
efficient handling of network traffic as well as to provide isolation on the network
Spanning Tree Protocol (STP)
A network protocol that is used to ensure a loop-free topology on switched Ethernet networks
Prevents loops and the broadcast radiation that results from them
Standardized as 802.1D with another variation known as Rapid STP (RSTP) 802.1w
Creates a spanning tree of links to a root switch to ensure that links that are not part of the
spanning tree are disabled, ensuring there is only one active connection between any two
network nodes

STP Port States
Based on STP ports, can have any of the following states:
Blocking
Listening
Learning
Forwarding
Disabled
The state of the port is determined initially when a device is connected to the port, using
information gathering frames known as Bridge Protocol Data Units (BPDUs)

RSTP Differences
Based on RSTP, switch ports can have the following states
Discarding
Learning
Forwarding
RSTP also adds additional bridge port roles in order to speed up convergence in the case of network
failures
Root
Designated
Alternate
Backup
Disabled

Trunking
Trunking typically refers to the process of carrying multiple VLANs over a single network link
between switches or routers. This allows for efficient use of network resources and simplifies
network management.
Trunking provides the ability for multiple VLANS to utilize a single connection and is made
simpler with trunking protocols.
Without VTP, you would be required to configure trunking on each switch
With VTP the configuration is greatly simplified

Trunking Protocols
Trunking protocols are also used with network switches in conjunction with the use of VLANs
Standardized as the VLAN Trunking Protocol (VTP) and IEEE 802.1Q
Carries multiple VLANs through a single link referred to as a trunk line and trunk port
Adds VLAN tags to the Ethernet frames in order to identify VLANs across multiple switches
ISL is the Cisco proprietary tagging protocol
IEEE 802.1q is the non-proprietary tagging protocol
When only a single VLAN exists there is no need for a trunking protocol, which is referred to as
Native VLAN or Default VLAN, and frames would be untagged

Additional Management for Switches
Management of switches varies in complexity and necessity
Creation of additional VLANs
 Larger environments
 Controlled environments
 Changing usernames and passwords
 ALWAYS
Enable AAA
 Higher security
Enable/Disable console port access
Configure virtual terminal (VTY) access and passwords

Layer 3 Functionality
A layer 3 device is primarily dealing with addressing and routing of packets
Routing is the process of selectively forwarding traffic from one network
Hardware or software routing
Use Layer 3 addressing to determine the route a packet should take
Routing tables are able to be updated manually (static routing) or dynamically using routing
protocols
The type of router used will vary based on the organization's requirements, connection types,
and size

Routing Tables
A routing table is a key component in networking that is used by routers to determine where
to forward data packets. It contains information about the available routes in a network,
along with metrics and next-hop addresses.
Routing tables are used by clients, servers, and routers in the same way to determine where
to forward network packets
Determine whether a host route exists in the routing table
Determine whether the destination is local or remote
Consult the routing table for a Network ID entry matching that of the destination host
Forward directly to the host or route to the default gateway
Routers work the same but are attached to multiple network segments

Network Segmentation Benefits
o There are various benefits to network segmentation that is provided by Layer 3 devices in the form
of subnetworks
o Benefits
o Separate public and private networks
o Optimize performance
o Minimize broadcast domains
o Control traffic to/from particular subnetworks
o Implement security controls
o Load balancing and high availability
o Create test networks and honeypots for security checks
o Compliance regulations

Hardware vs. Software Routers
Hardware routers are dedicated devices
o Inclusion of processor/memory/storage in which hardware routers are actually specialized
minicomputers with highly tailored I/O capabilities
o Multiple physical interfaces (ports)
Ethernet
Token Ring
RS-232
V.35
Broadband
FDDI
» Software routing is handled by a NOS and used in much smaller situations

Static vs Dynamic Routing
Routing categories are based on how routing decisions and updates occur
o Static routers
o Dynamic routers

Routing Protocols
Routing protocols are not used to route packets but instead to distribute route information
among routers so that they can route the packets correctly and efficiently
The routing protocol that is chosen will be based on
o Physical router type o Size of organization o Location of router (AS)
o Internal
o External
o High availability
o Performance requirements o Latency
o Convergence

Dynamic Routing
Dynamic routing means that routers are capable of communicating route information and
changes with one another in a timely fashion using routing protocols
Routing protocols fall into three distinct categories
o Distance-Vector
o Link-State
o Path-Vector

Metric
In networking, a metric is a value assigned to a route by a routing algorithm. The metric is used
to determine the best path among multiple routes to a particular destination. Routers use
metrics to make decisions about the most efficient and reliable routes in order to forward data
packets.
Different routing protocols use different metrics, and the specific metric used depends on the
routing algorithm in use. Here are some common routing protocols and their associated metrics:

Routing Information Protocol (RIP): RIP uses a simple hop count as its metric. The hop count is
the number of routers that a packet must traverse to reach the destination. The route with the
fewest hops is considered the best.
Open Shortest Path First (OSPF): OSPF uses cost as its metric. The cost is calculated based on
the bandwidth of the link. Routes with lower costs are preferred.
Enhanced Interior Gateway Routing Protocol (EIGRP): EIGRP uses a composite metric that
includes bandwidth, delay, reliability, and load. It is a more sophisticated metric compared to RIP
and OSPF, taking multiple factors into account.
Border Gateway Protocol (BGP): BGP uses various attributes, and the decision-making process is
more complex. BGP considers factors such as the Autonomous System Path, next-hop
information, and policy rules.

In the context of router metrics, administrators can sometimes manually configure static routes
with specific metrics to influence the routing decisions. This is particularly useful when multiple
routes to a destination exist, and the administrator wants to control which route is preferred.
It's essential to understand the metrics used by the routing protocols in your network, as they
influence the path selection and overall efficiency of data transmission. Different metrics may be
more suitable for specific network scenarios, and network administrators should consider the
requirements of their network when selecting or configuring routing metrics.

Path Vector
A Path Vector refers to a type of routing algorithm used to determine the best path for data to
travel from a source to a destination in a network. Two well-known examples of path vector
routing protocols are BGP (Border Gateway Protocol) and EIGRP (Enhanced Interior Gateway
Routing Protocol).
In a path vector routing algorithm, each router maintains a table that contains information
about the paths to various destinations. The routers exchange these path vectors with their
neighboring routers. The decision-making process involves selecting the best path based on the
accumulated path vector information.
The use of path vector routing helps prevent routing loops and allows routers to make more
informed decisions about the optimal paths for data transmission within a network. It also
provides a level of flexibility in route selection based on various attributes, contributing to
efficient and adaptable routing in complex network environments.

Interior Routing Protocols
Interior Routing Protocols, also known as Interior Gateway Protocols (IGPs), are used for routing
within an autonomous system (AS). An autonomous system is a collection of routers and networks
under the control of a single organization, typically sharing a common routing policy.
Routing Information Protocol (RIP):
◦ Type: Distance Vector Protocol
◦ Version: RIP version 1 (RIPv1) and RIP version 2 (RIPv2)
◦ Metrics: Hop count (number of routers between source and destination)
◦ Limitations: Convergence can be slow in large networks. Limited to 15 hops.
Open Shortest Path First (OSPF):
◦ Type: Link-State Protocol
◦ Features: Hierarchical structure, support for variable-length subnet masking (VLSM), and classless routing.
◦ Metrics: Cost based on link bandwidth.
◦ Use Case: Suited for larger networks and provides faster convergence than RIP.

Intermediate System to Intermediate System (IS-IS):
◦ Type: Link-State Protocol
◦ Features: Developed for ISO's OSI protocol suite. Commonly used in Service Provider networks.
◦ Metrics: Variable (based on configurable metric).
◦ Use Case: Suitable for large and complex networks.
Enhanced Interior Gateway Routing Protocol (EIGRP):
◦ Type: Advanced Distance Vector Protocol with Link-State elements
◦ Features: Cisco proprietary. Hybrid protocol that combines aspects of both distance vector and link-
state protocols.
◦ Metrics: Bandwidth, delay, reliability, and load.
◦ Use Case: Suited for Cisco environments, providing rapid convergence and low resource usage.

Exterior Routing Protocols
Exterior Routing Protocols, also known as Exterior Gateway Protocols (EGPs), are used for routing between
different autonomous systems (ASes). Unlike Interior Gateway Protocols (IGPs), which operate within a single
autonomous system, EGPs are designed to exchange routing information between autonomous systems.
Border Gateway Protocol (BGP):
◦ Type: Path Vector Protocol
◦ Use Case: Used for routing between different autonomous systems on the internet.
◦ Attributes: BGP uses a path vector algorithm to make routing decisions based on a variety of attributes, including AS path
length, origin, and various optional attributes.
◦ Features: BGP is a policy-based routing protocol, allowing network administrators to define routing policies based on factors
such as AS path, route preference, and community attributes.
◦ Reliability: BGP is designed to be highly scalable and reliable, making it suitable for the global internet.
Exterior Gateway Protocol (EGP):
◦ Type: Historic Protocol
◦ Use Case: Obsolete; replaced by BGP.
◦ Background: EGP was the first standardized EGP used on the early internet. It is now considered obsolete, and Border
Gateway Protocol (BGP) has replaced it.
◦ Limitations: EGP had limitations in terms of scalability and flexibility, which led to its replacement by BGP.

Key Differences:
BGP is the Dominant Exterior Routing Protocol: BGP is the primary exterior routing protocol
used on the modern internet. It is highly scalable and supports complex policy-based routing.
EGP is Obsolete: EGP was the original exterior routing protocol but is now considered obsolete.
It has been replaced by BGP due to its limitations.
In summary, BGP is the primary exterior routing protocol in use today, handling the complexities
of routing between different autonomous systems on the global internet. It plays a crucial role in
determining how traffic is routed between different networks, and its policy-based approach
allows for fine-grained control over routing decisions.

Routing Problems
Routing Loops:
Problem: Packets get stuck in a loop, unable to reach their destination.
Causes:
◦ Incorrect implementation of a routing algorithm.
◦ Slow convergence in distance vector protocols (e.g., RIP) leading to temporary loops.
◦ Misconfiguration of route summarization.
Load Balancing Problems:
Problem: Uneven distribution of traffic among multiple paths.
Causes:
◦ Incorrect configuration of load balancing mechanisms.
◦ Path selection based on suboptimal metrics.

Link Failures:
Problem: Loss of connectivity due to a physical link failure.
Causes:
◦ Hardware failures, cable issues, or other physical layer problems.
◦ Misconfiguration of interfaces.
Count to infinity
This problem arises when routers in a network are trying to converge after a link failure, and the
information about the failure takes time to propagate through the network. During this time,
routers may continue to advertise outdated or incorrect information, leading to an infinite loop
of updates.

Additional Network Devices
Gateways
 Device, software, or system that provides translation mechanisms between incompatible systems
 Translate between operating systems, network architectures, or e-mail formats
Switches
MultiLayer
 Performs both routing and switching
 Can go by many other names such as layer 2 router, layer 3 switch, or IP switch
 Can be used for QoS using DSCP (Differentiated Services Code Point)
Content
◦ Used for load balancing for server groups or firewalls
◦ Performs high-level switching based on groups, applications, or URLs o Complex to implement but provides
great load-balancing capabilities

VoIP Phones
Popular phone systems that use IP technology to transmit calls along with specialized protocols
VoIP phones
Soft phones
SIP and RTP protocols

Load Balancers
Hardware devices that are designed to split a particular network load across multiple
servers
Benefits
Increase the capacity of the system
Improve performance
Provide fault tolerance

Modem
Modem:
Modems (modulator-demodulator) convert digital data from a computer into analog signals for
transmission over analog communication lines (e.g., telephone lines) and vice versa.

Bridge
Network Bridge:
Bridges operate at the data link layer and connect different network segments. They filter traffic
based on MAC addresses, helping to reduce collision domains.

Traffic Shaper
Traffic shapers, also known as bandwidth shapers or bandwidth managers, are network devices
or software applications designed to control and manage the flow of network traffic to ensure
efficient and fair use of available bandwidth. Traffic shaping helps prevent network congestion,
prioritize critical applications, and optimize the overall performance of the network.
Bandwidth Control:
Traffic shapers control the rate of data transmission, limiting the amount of bandwidth that
specific users, applications, or types of traffic can consume. This prevents certain users or
applications from monopolizing the available bandwidth

Intrusion Prevention System (IPS)
An Intrusion Prevention System (IPS) is a security technology that monitors and analyzes
network and/or system activities for malicious or unwanted behavior. The primary goal of an IPS
is to identify and respond to security threats in real-time, preventing unauthorized access,
attacks, and the exploitation of vulnerabilities. IPS is a crucial component of a comprehensive
cybersecurity strategy.

Firewall
A firewall is a network security device or software that monitors and controls incoming and
outgoing network traffic based on predetermined security rules

Monitoring devices
Monitoring devices are tools and systems used to observe, measure, and analyze various aspects
of a network, system, or environment. These devices play a crucial role in maintaining the
health, performance, and security of IT infrastructures.
Network Monitors: Devices that analyze and report on the performance and status of network
infrastructure, including routers, switches, and servers. They provide insights into bandwidth
usage, latency, and overall network health.
Packet Sniffers: Tools that capture and analyze network traffic at the packet level. Packet sniffers
help identify network issues, troubleshoot problems, and analyze security threats.
Flow Analyzers: Devices that monitor network flows, providing visibility into the communication
patterns between devices. Flow analyzers assist in identifying anomalies and optimizing network
performance.

System Monitoring Devices:
Server Monitoring Tools: These tools monitor the performance, resource utilization, and health
of servers. They can track metrics such as CPU usage, memory usage, disk space, and server
uptime.
Application Performance Monitoring (APM) Tools: APM tools focus on monitoring the
performance of applications. They provide insights into application response times, transaction
errors, and user experiences.
Endpoint Security Solutions: Security monitoring tools on endpoints (computers, laptops,
mobile devices) that detect and respond to security threats, including antivirus software and
endpoint detection and response (EDR) solutions.

Internet of Things (IoT)
The Internet of Things (IoT) refers to the network of interconnected physical devices, vehicles,
appliances, and other objects embedded with sensors, software, and network connectivity,
allowing them to collect and exchange data. The concept of IoT revolves around the idea of
enabling everyday objects to communicate with each other and with central systems over the
internet.
Connectivity:
IoT devices are equipped with various communication technologies such as Wi-Fi, Bluetooth,
RFID, or cellular networks. This connectivity enables them to share data and communicate with
other devices or centralized systems.
Sensors:
IoT devices are equipped with sensors to collect data from their environment. Common sensors
include temperature sensors, motion sensors, accelerometers, humidity sensors, and more.
Actuators allow devices to perform actions based on the data received.

SCADA
Supervisory Control and Data Acquisition (SCADA) is a control system architecture that is used in
various industries to monitor and control processes, infrastructure, and facilities in real-time.
SCADA systems are typically employed in critical infrastructure sectors such as energy, water and
wastewater, manufacturing, transportation, and telecommunications.

DHCP
Dynamic Host Configuration Protocol (DHCP) is a network management protocol used to
automate the process of configuring devices on a network. It allows devices (such as computers,
printers, and other networked devices) to obtain necessary network configuration information,
including IP addresses, subnet masks, default gateways, and DNS server addresses, dynamically
from a central server.

Key aspects and functions of DHCP
IP Address Assignment: DHCP automatically assigns IP addresses to devices on a network. When
a device joins a network, it sends a DHCP request to the DHCP server, which then responds with
an available IP address from a predefined pool.
Dynamic Configuration: DHCP provides dynamic configuration, allowing devices to receive
different IP addresses each time they connect to the network. This is in contrast to static IP
addressing, where each device is manually assigned a fixed IP address.
Centralized Management: DHCP is typically managed by a central DHCP server. This
centralization makes it easier to control and monitor IP address assignments, configurations, and
troubleshooting.

Subnet Configuration: DHCP can also provide subnet masks, default gateway addresses, and
other network configuration parameters along with the IP address. This helps devices on the
network to correctly communicate with devices on different subnets.
DNS Configuration: DHCP can distribute DNS server addresses to devices, ensuring that they can
resolve domain names to IP addresses for network communication.
Reduced Administrative Overhead: Using DHCP reduces the administrative burden of manually
assigning and managing IP addresses for each device on a network. It simplifies the process of
adding or removing devices from the network.

Lease Duration: IP addresses assigned by DHCP are not permanent. Each address is leased to a device
for a specific duration. Before the lease expires, the device can request a lease renewal. If a device
disconnects from the network, its IP address can be reclaimed by the DHCP server for use by another
device.
DHCP Discover, Offer, Request, Acknowledge (DORA) Process: The process of a device obtaining an
IP address from a DHCP server follows the DORA sequence:
Discover: The client broadcasts a DHCP discover message to find available DHCP servers.
Offer: DHCP servers respond with a DHCP offer message, providing an available IP address.
Request: The client selects an offered IP address and sends a DHCP request message.
Acknowledge: The DHCP server acknowledges the request and allocates the IP address to the client.

Name Resolution
Name resolution is the process of mapping human-readable hostnames or domain names to IP
addresses on a computer network. It is a crucial aspect of networking, as it allows users to refer
to remote hosts using memorable names instead of numeric IP addresses. There are different
methods of name resolution, with the Domain Name System (DNS) being the most common
one.

DNS
The Domain Name System (DNS) is a hierarchical and distributed naming system that is
fundamental to the functioning of the internet. It translates human-readable domain names into
IP addresses, allowing users to access websites, send emails, and connect to various services
using easily memorable names rather than numeric IP addresses. Here are key aspects of DNS:

DNS Hierarchy:
◦ DNS operates in a hierarchical manner with different levels of servers responsible for different parts of
the domain name space.
◦ Root DNS servers are at the top, followed by TLD servers, authoritative DNS servers for specific domains,
and local DNS resolvers.
DNS Resolution Process:
◦ When a user types a domain name into a web browser or application, the local DNS resolver is queried.
◦ If the resolver has the IP address in its cache, it provides the answer. Otherwise, it queries the root DNS
servers, then TLD servers, and finally the authoritative DNS server for the specific domain to obtain the
IP address.

DNS Records:
DNS records contain information associated with domain names. Common types include:
◦ A (Address) Record: Maps a domain to an IPv4 address.
◦ AAAA (IPv6 Address) Record: Maps a domain to an IPv6 address.
◦ MX (Mail Exchange) Record: Specifies mail servers for the domain.
◦ CNAME (Canonical Name) Record: Alias of one domain to another.
◦ PTR (Pointer) Record: Used for reverse DNS lookup.
◦ NS (Name Server) Record: Specifies authoritative DNS servers for the domain.

Public and Private DNS:
◦ Public DNS servers are operated by ISPs or third-party providers (e.g., Google's 8.8.8.8). They resolve
domain names for internet users.
◦ Private DNS servers are often used within organizational networks to handle internal domain
resolutions.
DNS is a critical component of the internet infrastructure, enabling the seamless and user-
friendly interaction between users and online resources. It plays a crucial role in ensuring the
reliability and accessibility of internet services.

DNS Zones & Domains
Forward Lookup:
◦ Definition: In a forward lookup, a domain name is used to find the corresponding IP address.
◦ Process: When a user or application wants to access a website or connect to a server using its domain
name (e.g., www.example.com), a forward lookup is performed to obtain the associated IP address.
◦ Example: If you enter "www.google.com" into a web browser, the browser performs a forward lookup
to find the IP address (e.g., 172.217.9.164) associated with that domain.
Reverse Lookup:
◦ Definition: In a reverse lookup (also known as reverse DNS lookup), an IP address is used to find the
corresponding domain name.
◦ Process: When a system needs to determine the domain name associated with a specific IP address, a
reverse lookup is performed. This is often used in logging, security, and mail server configurations.
◦ Example: If you have an IP address like 8.8.8.8, a reverse lookup might reveal that it corresponds to the
domain name "dns.google."

Forward Lookup Example:
User types "www.example.com" into a web browser.
The local DNS resolver is queried for the IP address associated with "www.example.com."
The DNS resolver checks its cache; if the information is not there, it queries the authoritative
DNS server for the "example.com" domain.
The authoritative DNS server responds with the IP address (e.g., 203.0.113.10).
The web browser uses the obtained IP address to establish a connection to the server hosting
"www.example.com."

Reverse Lookup Example:
A system administrator notices an IP address (e.g., 203.0.113.10) in server logs.
The administrator performs a reverse lookup to find the corresponding domain name.
The DNS resolver is queried for the domain name associated with the IP address.
The DNS resolver checks its cache; if the information is not there, it queries the appropriate
reverse DNS zone.
The reverse DNS zone responds with the domain name (e.g., server.example.com).

VPN
A VPN, or Virtual Private Network, is a technology that allows you to create a secure and
encrypted connection to another network over the Internet. It provides a secure way for
individuals and organizations to access resources, share data, and communicate over a public
network like the internet.

Security: VPNs use encryption to ensure that data transmitted between your device and the
VPN server is secure and protected from eavesdropping or unauthorized access. This is
particularly important when using public Wi-Fi networks.
Privacy: VPNs can help protect your online privacy by masking your IP address. This makes it
more difficult for websites and online services to track your online activities.

Anonymity: While VPNs provide some level of anonymity by hiding your IP address, it's essential
to note that they don't make you completely anonymous online. Other factors, such as your
online behavior and the websites you visit, can still be tracked.
Access Control: VPNs allow users to access resources on a private network from anywhere with
an internet connection. This is especially useful for remote workers or individuals who need to
access resources that are restricted to a specific location or network.
Bypassing Geo-restrictions: VPNs can be used to bypass geographic restrictions imposed by
certain websites or streaming services. By connecting to a server in a different location, you can
appear as if you're accessing the internet from that location.

Types of VPNs: There are different types of VPNs, including remote access VPNs, site-to-site
VPNs, and peer-to-peer VPNs. Remote access VPNs are commonly used by individuals to
connect to a private network over the internet. Site-to-site VPNs connect entire networks
together, often used by businesses with multiple locations.

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