CISCO 1 (incomplete)

MODULE 1 (Networking Today)

• Communication is almost as important to us as our reliance on air, water, food, and shelter.

• Networking today has no boundaries, which connects global communities and create human network.

Network Components

HOST ROLES

• every computer on a network is called a host or end device.

• Servers are computers that provice information to end devices:

  • email servers

    • clients use client software to access email

• web servers

  • clients use browser software to access web pages

• file server

  • stores corporate and user files; client devices access these files

• Clients are computers that send requests to the servers

PEER-TO-PEER

• A device to be a client and a server in a peer-to-peer network

• ADVANTAGES

  • Easy to set up

  • Less complex

  • Lower cost

  • used for simple tasks

• DISADVANTAGES

  • no centralized administration

  • not as secure

  • not scalable

  • slower performance

END DEVICE

• A message originates fromor where it is received.

• data from end device → network → another end device

INTERMEDIARY NETWORK DEVICES

• it interconnects end devices

  • ex. switches, wireless access points, routers, and firewalls

• ROLE OF AN INTERMEDIARY DEVICE:

  • management of data as it flows through a network

  • regenerate and retransmit data signals

  • maintain information about what pathway exist

  • notify other devices of errors

NETWORK MEDIA

• communication is carried through a medium

• MEDIA TYPES

  • Metal wires within cables

    • uses electrical impulses

  • Glass or plastic fibers within cable (Fiber-optic cable)

    • pulses of light

  • wireless transmission

    • uses modulation of specific frequencies of electromagnetic waves.

• 
  

Network Representations and Topologies

NETWORK REPRESENTATIONS

    NETWORK DIAGRAMS/TOPOLOGY DIAGRAMS

• uses symbols to represent devices within the network

    Important Terms:

• Network Interface Card (NIC)

  • Hardware that connects a device to a network

• Physical Port

  • socket on a device where cables are plugged in

• Interface

  • connection point used for network communication

TOPOLOGY DIAGRAMS

    PHYSICAL TOPOLOGY

• illustrates the physical location of intermediary devices and cable installation

    LOGICAL TOPOLOGY

• illustrates devices, ports, and the addressing scheme

Common Types of Networks

NETWORK OF MANY SIZES

    Small Home Networks

• Connects a few computers to each other and the internet

    Small Office/Home Office

• enables computer within a home or remote office to connect to a corporate network

    Medium to Large Networks

• hundreds or thousands of interconnected computers

    World Wide Network

• connects hundreds of millions of computers world wide (Internet)

LANs AND WANs

LAN (Local Area Network)

• spans a small geographical area

• limited area

• administered by a single organization or individual

• provide high-speed bandwidth

WAN (Wide Area Network)

• spans a wide geographical area

• interconnect LANs over wide geographical areas

• administered by one or more service providers

• provide a slower sleep links between LANs

INTERNET

• worldwide collection of interconnected LANs and WANs

• LANs are connected to each other using WANs

• WANs may use copper wires, fiber optic cables, and wireless transmissions

• not owned by any individual or group

• developed to maintain structure on the internet:

  • IETF (Internet Engineering Task Force)

    • develops and maintains internet standards and protocols

  • ICANN (Internet Corporation for Assigned Names and Numbers)

    • manages domain names and IP address allocation

  • IAB (Internet Architecture Board)

    • Oversees the technical development and architecture

INTRANETS AND EXTRANETS

INTRANET

• private collection of LANs and WANs internal

• accessible only to the organizations members or others with authorization

EXTRANET

• for individuals who work for a different organization that need access to their data on their network.

Internet Connections

INTERNET ACCESS TECHNOLOGIES

    ways to connect users and organizations to the internet:

• Broadband cable, broadband digital subscriver line (DSL), wireless WANs, and mobile servies are used for home users and small offices.

• Organizations need faster connections

• business-class interconnections are usually provided by service providers (SP) (may include business DSL, leased lines, and metro ethernet)

HOME AND SMALL OFFICE INTERNET CONNECTIONS

Connections:

• Cable

  • internet offered by cable television service providers

• DSL (Broadband digital subscriber)

  • runs over a telephone line)

• Cellular

  • cellphone network

• Satellite

  • major benefit to rural areas without internet service providers

• Dial-up telephone

  • uses modem

BUSINESS INTERNET CONNECTIONS

Requires:

• higher bandwidth

• dedicated connections

• managed services

Types of Connection

• Dedicated Leased Line

  • reserved circuites within the service provider’s network

  • connects distant offices

• Ethernet WAN

  • extends LAN access technology into the WAN

• DSL

  • available in various formats including Symmetric Digital Subscriber Lines (SDSL)

• Satellite

  • provides connection when a wires solution is not available

THE CONVERGING NETWORK

• carries multiple services on one link:

  • data

  • voice

  • video

• can deliver over the same network infrastructure

Reliable Networks

NETWORK ARCHITECTURE

• technologies that support infrastructure that moves data across the network

• 4 basic characteristics to meet user expectations:

1. Fault Tolerance

• limits the impact of a failure

• limiting the number of affected devices

• multiple paths are required for fault tolerance

    Packet Switched Network:

• splits traffic into packets that are routed over a network

• each packet could theoretically take a different path to the destination

* Not possible with circuit-switched networks

2. Scalability

• expands quickly and easily to support new users and applications

3. Quality of Service

• primary mechanism used to ensure reliable delivery of content

• with QoS policy in place, the rother can more easily manage the flow of data and voice traffic

4. Network Security

2 main types of network security

• Network infrastructure security

  • physical security of network devices

  • prevents unauthorized access

• Information security

  • protects the information or data transmitted

3 main goals

• confidentiality

  • only intended recipients can read the data

• integrity

  • assurance that the data has not been altered during transmission

• availability

  • assurance of timely and reliable access

Network Trends

Recent Trends

1. Bring your Own Device (BYOD)

• allows end users to have the freedome to user personal tools to access information and communicate

• gives them more opportunities and greater flexibility

• any device, used anywhere

2. Online Collaboration

• collaborate over the network on joint proects

3. Video Communication

• video call are made to anyone

• powerful tool for communicating with others

• video is becoming critical requirement

4. Cloud Computing

• stores personal files

• backups our data on servers over the internet

• allows businesses to deliver to any device anywhere in the world

4 types of clouds:

• Public Coulds

  • available to the general public

• Private Clouds

  • for specific organizations

• hybrid clouds

  • made up of 2 or more cloud types (ex. part custom and part public)

• custom clouds

  • built to meet the needs of a specific industry

  • can be private or public

TECHNOLOGY TRENDS IN THE HOME

• smart home technology

  • allows technology to be integrated into every-day appliances

POWERLINE NETWORKING

• allows devices to connect to a LAN where data network cables or wireless communications are not a viable option

• useful when wireless access points cannot reach all the devices in the home

WIRELESS BROADBAND

• another option used to connect homes and small businesses to the internet

• Wireless Internet Service Provider (WISP connects subscribers to designated access points or hotspots (Commonly found in rural environments)

• another solution for the home and small businesses

• an antenna is installed outside the hosue

Network Security

SECURITY THREATS

• an integral part of networking regardless of the size of the network

• must take into account the environment

• involves many protocols, technologies, devices, tools, and techniques to secure data

• threat vectors might be external or internal

    external threats (outside the organization):

• viruses, worms. tojan horses

• spyware and adware

• zero-day attacks

• threat actor attacks

• denial of service attacks

• data interception and theft

• identity theft

    internal threats (inside the organization):

• lost or stolen devices

• accidental misuse by employees

• malicious employees

SECURITY SOLUTIONS

• additional security reqs.:

  • dedicated firewall system

  • access control lists (ACL)

  • intrusion prevention systems (IPS)

  • Virtual private networks (VPN)

MODULE 2 (Basic Switch and End Device Configuraiton)

Cisco IOS Access

OPERATION SYSTEMS

• shell

  • allows users to request specific tasks from the computer

• kernel

  • communicates between the hardware and software of a computer

• hardware

  • physical part of a computer

GUI

• allows users to interact with the system using graphical icons, menus, and windows

• user friendly and requires less knowledge

• can failm crash, or simply not operate as specified

• network devices are typically accessed through CLI

PURPOSE OF AN OS

• allows users to use a mouse to make selections and run programs

• allows users to enter text and text based commands

• CLI based network OS enables a network technician to:

  • use keyboard to run CLI based network programs

  • use keuboard to enter text and text based commands

  • view output on a monitor

ACCESS METHODS

• console

  • physical management port

• secure shell (SSH)

  • establishes a secure remote CLI connection through virtual interface

• telnet

  • establishes an insecure remote CLI connection

TERMINAL EMULATION PROGRAMS

• used to connect to a network device by either a console port or by an SSH/Telnet connection

IOS Navigation

PRIMARY COMMAND MODES

    user EXEC mode:

• allows acces to only a limited number of basic monitoring commands

• identified by the CLI prompt that ends with the > symbol

    privileged EXEC mode:

• allows access to all ommands and features

• ends with the # symbol

CONFIGURATION MODE AND SUBCONFIGURATION MODES

    gloval configuration mode:

• used to access configuration oprtions

    line configuration mode:

• used to configure console, SSH, telnet, or AUX access

    interface configuration mode:

• used to configure a switch port or router interface

NAVIGATION BETWEEN IOS MODES

    privileged EXEC mode:

• moves from user EXEC mode to privilede EXEC mode

• use the enabled command

    global configuration mode:

• move in and out of global configuration mode

• use the configure terminal command

• to return to privilege EXEC mode, use exit command

    line configuration mode:

• move in and out of configuration mode

• line command followed by the management line type

• use exit command to return to global config mode

subconfiguraiton modes:

• to move out of any subconfig mode to return to global config mode, use exit command

• to return to privilege EXEC mode, use end command or key combination ctrl + z

• to move directly from one subconfig mode, type the desired subconfig mode command

  • ex. (config-line)# to (config-if)#

The Command Structure

BASIC IOS COMMAND STRUCTURE

• keyword

  • a specific parameter defined in the operating system (ip protocols)

• argument

  • not predefined; value defined by the user (192.168.10.5)

ex.

prompt → switch

command → show

space

keyword → ip protocols

argument → 192.168.10.5

IOS COMMAND SYNTAX CHECK

• a command might require one or more args.

• boldface

  • indicated commands and keywords that you enter literally as shown

• italics

  • you supply values

• [ ]

  • indicates an optional element

• { }

  • indicates a required element

• [ { | } ]

  • indicates required choice within an optional element.

  • spaces are used to clearly delineate parts of the command

• command syntax provides the pattern, or format that must be used when entering a command

IOS HELP FEATURES

2 forms of help available:

• context-sensitive help

  • enables you to quickly find answers to these questions:

    • which commands are available in each command mode

    • which commands start with specific characters or group of characters

    • which argument and keuwords are available to aprticular commands

ex.

• command syntax check

  • verifies that a valid command was entered by the user

ex.

HOT KEYS AND SHORTCUTS

• IOS CLI privdes hotkeys and shortcuts

• commands and keywords can be shortened to the minimum number of characters that indetify a unique selection

keystrokes

• tab

  • completes a partial command name entry

• backspace

  • erases the character to the left of the cursor

• left arrow or ctrl+b

  • moves the cursor one character to the left

• right arrow or ctrl f

  • move the cursor one character to the right

• up arrow or ctrl p

  • recalls the commands in the history buffer

• enter key

  • displays the next line

• space bar

  • next screen

• any other key

  • ends the display string, returning to privileged EXEC mode

• ctrl c or ctrl z

  • ends the config mode and returns to privileged EXEC mode

• ctrl shift 6

  • all purpose break sequence used to abort DNS lookups, traceroutes, pings, etc.

Basic Device Config

DEVICE NAMES

• first config command should be to give it a unique hostname

• all devices are assigned a factory default name

  • ex. Cisco IO

  • 
    S switch is “switch”

• Guidelines for naming devices:

  • start with a letter

  • contain no spaces

  • end with a letter or digit

  • use only letters, digits, and dashes

  • less than 64 characters

PASSWORD GUIDELINES

• all networking devices sould limit administrative access by securing priveleged EXEC, user EXEC and remove Telnet access with passwords

• Password Guidelines:

  • more than 8 characters

  • use a combination of upper and lowercase letters, numbers, special characters, and/or numeric sequence

  • avoid using the same pass. for all devices

  • do not use common words

CONFIG PASSWORDS

securing user EXEC mode access:

• enter line console 0 in global config mode

• specify the user EXEC mode password using the password command

• enable user EXEC access using the login command

securing privileged EXEC mode access:

• enter global config mode

• use the enable secret password command

securing VTY line access:

• enter line VTY config mode using the line vty 0 15 command in global config mode

• specify VTY password using the password command

• enable VTY access using the login command

ENCRYPT PASSWORDS

• start up config and running config files display passwords in plaintext

• service password-encryption command

  • to encrypt plaintext passwords

  • show running config to verify passwords are encrypted

BANNER MESSAGES

• it is to warn unauthorized personnel from attempting to access the device

• enter banner motd #

  • motd = message of the day

  • # = global config (delimiting character; entered before and after the message)

Save Configuration

CONFIGURATION FILES

2 system files that sotre the device configuration:

• startup-config

  • file that is stored in NVRAM

• running-config

  • stored in RAM

to save changes, enter copy running-config start-up config privileged EXEC mode command

ALTER THE RUNNING CONFIGURATIONS

• you can restore the device to its previous configuration

  • remove changed commands → reload command in privilege EXEC mode

• if undesired changes were saved to the startup-config, it may be necessary to clear all the configurations using the erase setup config command in privilege EXEC mode

  • remove changed commands → reload command in privilege EXEC mode → erase setup config command → reload the device to clear the running config from RAM

CAPTURE CONFIGURATION TO A TEXT FILE

• Configuration files can also be saved and archived to a text document

open terminal emulation software that is connected to a switch → enable loggin in to the terminal → assign a name and file location → execute the show running config or show startup config command at the privileged EXEC prompt → disable logging in the terminal software by choosing the None sessions

Ports and Addresses

IP ADDRESSES

• primary means of enabling devices to locate one another

• establishes end-to-end communication on the internet

• IPv4 Address

  • Dotted decimal notation

    • structure of IPv4 address

    • represented by 4 decimal numbers between 0 and 255

  • IPv4 subnet mask is 32 bit value

• IPv6 Address

  • 128 bits in length

  • written as a string hexadecimal values

  • every 4 bits represents a single hexadecimal digit

    • total of 32 hexadecimal values

  • groups of 4 hexadecimal digits are separated by a colon :

  • not case sensitive

INTERFACE AND PORTS

• types of network media include:

  • twisted pair copper cables

  • fiber-optic cables

  • coaxial cables

  • wireless

• some of the difference between various types of media:

  • distance the media can successfully carry a signal

  • environment in which the media is to be installed

  • amount of data and the speed at which it must be transmitted

  • cost of the media and installation

Configure IP Addressing

MANUAL IP ADDRESS CONFIGURATION FOR END DEVICES

• end devices on the network need an IP address to communicate with other devices

• IPv4 info can be entered into end devices manually or automatically using Dynamic Host Configuration Protocol (DHCP)

Manually configure:

control panel → network sharing center → change adapter settings (choose the adapter) → right click and select properties → click properties to open the IPv4 window → configure

AUTOMATIC IP ADDRESS CONFIGURATION FOR END DEVICES

• DHCP enables automatic IPv4 address configuration for every end device that is DHCP enabled

To configure DHCP:

control panel → network sharing → change adapter settings (choose the adapter) → rick click and select properties to display teh Local Area Connection Properties → click properties → select obtain an IP address automatically and Obtain DNS server address automatically

SWITCH VIRTUAL INTERFACE CONFIGURATION

• to access the switch remotely, an IP address and a subnet mask must be configured on the SVI

to configure an SVI on a switch:

enter the interface vian 1 command in global config mode → assign an IPv4 address using the ip address ip-address subnet-mask command → enable the virtual interface using the no shutdown command

MODULE 3 (Protocol Models)

1. The Rules of Communication

Fundamental Elements

• Source (Sender): The device initiating the communication.

• Destination (Receiver): The device intended to receive the message.

• Channel (Media): The path or medium through which communication occurs (e.g., cables, wireless).

Protocols

• Definition: Protocols are sets of rules that define how devices communicate over a network.

• Purpose: Ensure that devices can understand each other and successfully exchange data.

protocols must account for the following requirements:

• an identified sender and receiver

• common languages and grammar

• speed and timing of delivery

• confirmation or acknowledgement requirements

Key Protocol Requirements

• Message Encoding: Converting information into a transmittable format (e.g., bits, light, sound).

• Message Formatting & Encapsulation: Structuring data for transmission, including adding headers and trailers.

  • uses a specific format or structure

  • formats depends on the type of message and the channel used

• Message Size: Determining how much data can be sent at once.

  • converted to bits

    • encoded into a pattern of light, sound, or electric impulses

  • destination host decodes sthe signals

• Message Timing: 

  • Flow Control: manages the rate of data transmission

  • Response Timeout: manages how long a device waits

  • Access Method: determines when someone can send a message

Collisions:when more than one device sends traffic at the same time (message becomes courrupt)

• Message Delivery Options:

  • Unicast: One-to-one communication.

  • Multicast: One-to-many (but not all).

  • Broadcast: One-to-all (used in IPv4, not in IPv6).

NODE ICON:

• documents may use the node icon

• a circle, to represent all devices

2. Protocols and Their Functions

Can be implemented on devices in:

• software

• hardware

• both

Protocols have their own:

• function

• format

• rules

Types of Protocols

• Network Communications: Enable device-to-device communication.

• Network Security: Provide authentication, data integrity, and encryption.

• Routing: Allow routers to exchange information and select optimal paths.

• Service Discovery: Automatically detect devices/services on the network.

Protocol Functions

• Addressing: Identifies sender and receiver.

• Reliability: Guarantees delivery of data.

• Flow Control: Manages data transmission rate.

• Sequencing: Labels data segments for correct reassembly.

• Error Detection: Checks for data corruption.

• Application Interface: Enables process-to-process communication.

Examples of Protocols

• HTTP (Hypertext Transfer Protocol): Governs web server-client interactions.

• TCP (Transmission Control Protocol): Manages conversations, ensures delivery, and flow control.

• IP (Internet Protocol): Delivers messages globally.

• Ethernet: Handles local delivery on LANs.

3. Protocol Suites

Definition

• A protocol suite is a group of related protocols that work together to enable communication.

Common Protocol Suites

• TCP/IP: The most widely used, maintained by IETF (Internet Engineering Task Force).

  • used by the internet

  • freely available to the public

  • standards-based protocol suite

  • Process:

    • web server encapsulating and sending a web page to a client

    • client de-encapsulating the web page

• OSI (Open Systems Interconnection): Developed by ISO (International Organization for Standardization) and ITU (International Telecommunications Union).

• AppleTalk & Novell NetWare: Proprietary suites.

Layered Approach

• Higher Layers: Deal with application and user interaction.

• Lower Layers: Handle data movement and provide services to upper layers.

4. Standards Organizations

Purpose

• Promote interoperability, competition, and innovation through open standards.

Open standards encourage:

• interoperability

• competition

• innovation

standards organizations are:

• vendor- neutral

• non profit organizations

• established to develop and promote the concept of open standards

Key Organizations

Internet Standards:

• ISOC (Internet Society): Oversees internet development.

• IAB (Internet Architecture Board): Manages and develops internet standards.

• IETF (Internet Engineering Task Force): Develops and maintains internet and TCP/IP technologies.

• IRTF (Internet Research Task Force): Focuses on long-term research.

• ICANN (Internet Corporation for Assigned Names and Numbers) & IANA (Internet Assigned Numbers Authority): Manage IP addresses, domain names, and protocol identifiers.

Electronic and Communications Standards

• IEEE (Institute of Electrical and Electronics Engineers): Creates standards for networking and telecommunications.

• EIA (Electronic industries Alliance): develops standards in electrical wiring and connectors

• TIA (Telecommunications Industry Association): develops communication standards in radio equipment, cellular towers, Voice over IP devices, satellite communications, and more

• ITU-T (International Telecommunications Union-Telecommunication Standardization Sector): Defines standards for video, IPTV (Internet Protocol Television), and broadband.

5. Reference Models

Benefits of Layered Models

• Simplify complex networking concepts.

• Assist in protocol design and foster vendor competition.

• Isolate changes to specific layers.

• Provide a common language for networking.

OSI Model (7 Layers)

1. Application: Process-to-process communication.

2. Presentation: Data representation and encoding.

3. Session: Manages data exchange sessions.

4. Transport: Segments, transfers, and reassembles data.

5. Network: Handles data exchange across networks.

6. Data Link: Manages data frames over media.

7. Physical: Physical connection and transmission.

TCP/IP Model (4 Layers)

1. Application: User data, encoding, dialog control.

2. Transport: Device communication across networks.

3. Internet: Path determination and logical addressing.

4. Network Access: Hardware and media control.

Comparison

• OSI is more granular (7 layers), TCP/IP is more practical (4 layers).

• OSI divides network access and application into more layers.

• TCP/IP does not specify which protocols to use when transmitting over a medium while OSI layer 1 and 2 discuss the necessary procedures

6. Data Encapsulation

Process

• Segmenting: Breaking messages into smaller units for efficiency and speed.

• Sequencing: Numbering segments for correct reassembly.

• Encapsulation: Each layer adds its own header (and sometimes trailer) to the data.

  • top down process

  • moves down the stack

Protocol Data Units (PDUs)

• Data (Application Layer)

• Segment (Transport Layer)

• Packet (Network Layer)

• Frame (Data Link Layer)

• Bits (Physical Layer)

De-encapsulation

• As data moves up the stack at the destination, each layer removes its header and processes the data.

7. Data Access and Addressing

Layer 3 (Network Layer) Addressing

• delivers the IP packet from source to destination

• IP Addresses:

  • Source IP: Original source of the packet.

  • Destination IP: Final destination of the packet.

  • Network Portion (IPv4) or Prefix (IPv6): Identifies the network group.

    • left-most part of the address

  • Host Portion (IPv4) or Interface ID (IPv6): Identifies the specific device.

    • remaining part of the address

Layer 2 (Data Link Layer) Addressing

• delivers the data link frame from one network interface card (NIC) to another NIC on the same network

• MAC Addresses:

  • Used for local delivery on the same network segment.

  • Source MAC: Sending device's NIC.

  • Destination MAC: Receiving device's NIC or router interface.

Same Network vs. Remote Network

• Same Network:

  • Source and destination share the same number in network portion in their IP addresses.

  • Data link layer uses actual MAC addresses of devices.

• Remote Network:

  • Source and destination have different network portions.

  • Data is sent to the default gateway (router), which forwards it to the remote network.

  • MAC addresses change at each hop, but IP addresses remain the same.

8. Summary Table: OSI vs. TCP/IP Layers

MODULE 4 (phyiscal Layer)

1. Purpose of the Physical Layer

• Physical Connection:

  • Before network communication, a device must be physically connected (wired or wireless) to the network.

  • Devices use Network Interface Cards (NICs) to connect; some have multiple NICs (wired and wireless).

  • Not all physical connections offer the same performance.

• Role of the Physical Layer:

  • Transports bits across the network media.

  • Accepts frames from the Data Link Layer, encodes them as signals, and transmits them as signals, and transmits them.

  • This is the final step in encapsulation before transmission.

  • The next device decodes the bits, re-encapsulates the frame, and processes it.

2. Physical Layer Characteristics

• Physical Layer Standards:

  • Governed by organizations like ISO, EIA/TIA, ITU-T, ANSI, IEEE.

  • Standards cover three areas: Physical Components, Encoding, and Signaling.

• Physical Components:

  • Hardware devices, media, connectors (e.g., NICs, cables, connectors).

• Encoding:

  • Converts bit streams into recognizable formats for the next device.

  • Examples: Manchester, 4B/5B, 8B/10B encoding.

• Signaling:

  • Represents bit values (1s and 0s) on the medium.

  • Varies by medium: electrical signals (copper), light pulses (fiber), microwaves (wireless).

• Bandwidth:

  • Capacity of a medium to carry data (measured in bps, Kbps, Mbps, Gbps, Tbps).

  • Influenced by media properties, technology, and physics.

• Latency:

  • Time (including delays) for data to travel from source to destination.

• Throughput:

  • Actual rate of successful data transfer over a period.

• Goodput:

  • Usable data transferred (Throughput minus overhead).

3. Copper Cabling

• Characteristics:

  • Most common, inexpensive, easy to install, low resistance.

  • Limitations: Attenuation (signal loss over distance), susceptible to EMI (Electromagnetic Interference)/RFI (Radio Frequency Interference) and crosstalk.

• Mitigation:

  • Adhere to cable length limits, use shielding/grounding, twist wire pairs.

• Types:

  • UTP (Unshielded Twisted Pair): Most common, uses RJ-45 connectors, relies on twisting for interference protection.

  

  • STP (Shielded Twisted Pair): Better noise protection, more expensive, harder to install, uses shielding.

  

  • Coaxial Cable: Used for wireless antennas and cable internet; consists of jacket, braid/foil, insulation, and conductor.

4. UTP Cabling

• Properties:

  • Four pairs of color-coded wires, no shielding, relies on cancellation and varied twists to limit crosstalk.

• LAN Standards:

  • TIA/EIA-568 (cable types, lengths, connectors, termination, testing).

  • IEEE defines electrical performance (Category 3, 5, 5e, 6).

• Connectors:

  • RJ-45 is standard; proper termination is crucial.

• Cable Types:

  • Straight-through: Both ends T568A or T568B; used for host-to-network device.

  • Crossover: One end T568A, other T568B; used for host-to-host, switch-to-switch, router-to-router (now mostly legacy due to Auto-MDIX).

  • Rollover: Cisco proprietary; used for console connections.

5. Fiber-Optic Cabling

• Properties:

  • More expensive, ideal for long distances and high bandwidth, immune to EMI/RFI, uses glass fibers and light pulses.

• Types:

  • Single-Mode Fiber (SMF): Small core, uses lasers, long distances.

  • Multimode Fiber (MMF): Larger core, uses LEDs, shorter distances (up to 550m at 10Gbps), more dispersion.

• Usage:

  • Enterprise Networks - backbone cabling

  • FTTH (Fiber-to-the-Home) - provides always-on broadband service

  • long-haul networks - connects countries and cities

  • submarine cables networks - survives in harsh undersea environments

• Connectors:

  • ST (Straight Tip)

  • SC (Subscriber Connector)

  • LC (Lucent Connector)

  • duplex multimode LC.

• Patch Cords:

  • SC-SC MM

  • LC-LC SM

  • ST-LC MM

  • ST-SC SM.

• Color Coding:

  • Yellow for SMF, orange/aqua for MMF.

• Comparison with Copper (UTP):

  • Fiber supports higher bandwidth, longer distances, is immune to EMI/RFI and electrical hazards, but is more expensive and requires more skill to install.

6. Wireless Media

• Properties:

  • Uses electromagnetic signals (radio/microwave), offers mobility, but has limitations (coverage, interference, security, shared medium).

• Limitations:

  • Coverage affected by environment

  • susceptible to interference

  • security risks (no physical access needed)

  • shared bandwidth

• Standards:

  • Wi-Fi (IEEE 802.11) - Wireless LAN (WLAN)

    • allows you to move freely (mobility)

  • Bluetooth (IEEE 802.15) - Wireless Personal Area Network (WPAN)

  • WiMAX (IEEE 802.16) - point-to-multipoint topology

  • Zigbee (IEEE 802.15.4). - low data-rate, primarily for Internet of Things (IoT) applications

• wireless data communications cover both data link and physcial layers

  • physical layer specifications:

    • data to radio signal encoding methods

    • frequency and power transmission

    • signal reception and decoding requirements

    • antenna design and construction

• Devices:

  • Wireless Access Point (AP) - concentrate wireless signals from users

    • connects to the existing copper-based network

  • Wireless NIC adapters - wireless communications capability to network hosts

• Security:

  • Strong security policies are essential to protect WLANs.

MODULE 5 (Number Systems)

Binary and IPv4 Addresses

• Bits

  • numbering system consists of 1s and 0s

• Decimal numbering system

  • consists of digits 0 through 9

• hosts, servers, and network equiptments uses binary addressing to identify each other

• addresses is made up to 32 bits

• Octets - addresses divided into 4 sections

  • contains 8 bits or 1 byte

  • separated by a dot

IPv4 Addresses

• routers and computers only understand binary

• human understands decimal

Binary Positional Notation

• a digit represents different values depending on the position the digit occupies in the sequence of numbers

Binary to Decimal

Step 1: write the simple chart from right to left

Step 2: place your binary number under the simple chart

Step 3: Add the numbers that have 1 under them

128+32+8+4=172

Decimal to Binary

Step 1: Start in the 128 position (highest position), check if the decimal number is greater than the position

• 186 > 128

• 12>128

Step 2: if yes, add 1 and subtract the decimal number to the position. If not enter 0 and move to the next position

Hexadecimal Number System

Hexadecimal

• converting hexadecimal to decimal is crucial in understanding IPv6

• base 16 numbering system

  • using digits 0 to 9

  • letters A to F

• easier to express a value as a signle hexadecimal than a 4 binary bit

• used to represent IPv6 addresses and MAC addresses

IPv6 Addresses

• 128 bits

  • every 4 bits represents a single hexa digit

    • total of 32 hexa values

  • Hextet - for hexa character group

Conversions

conversion table

• A = 10

• B = 11

• C = 12

• D = 13

• E = 14

• F = 15

DECIMAL TO HEXADECIMAL:

Step 1: Convert the decimal number to 8-bit binary string

Decimal: 15

Step 2: Split the binary string into 4 groups

Step 3: Convert each 4-bit group into hexa by adding each position that has 1 below it

Hexadecimal: 0F

HEXADECIMAL TO DECIMAL:

Step 1: Write out each hex and convert any letter to decimal

Hex: CB

C = 12

B = 11

Step 2: Multiply each digit by 16 raised to its positional power, starting from 0 on the right

12 × 16^1 = 192

11 × 1(16^0) = 11

Step 3: Add all the products together

192 + 11 = 203

Decimal: 203

HEXADECIMAL TO BINARY:

Step 1: separate the hex number into individual digits

Hex: CB

C (12) =

B (11) =

Step 2: convert each individual digit into its 4-bit binary using the 8, 4, 2, 1 place value chart

Step 3: Combine

11001011

MODULE 6 (Data Link Layer)

Purpose of the Data Link Layer

• responsible for communications between end-device NICs (Network Interface Card)

• allows upper layer protocols to access the physical layer media

• encapsulates layer 3 packets (IPv4 and IPv6) into layer 2 frames

• performs error detection

DATA LINK SUBLAYERS

• its standards are specific to the type of network (ethernet, WLAN, WPAN, etc.)

• 2 sublayers:

  • Logical Link Control (LLC): communicates between the networking software at the upper layers and device hardware at the lower layers.

  • Media Access Control (MAC): Responsible for data encapsulation and media access control

PROVIDING ACCESS TO MEDIA

• packets exchange between nodes may experience numerous data link layers and media transitions

• at each hop, a router performs 4 basic layer 2 functions:

  • accepts a frame from the network medium

  • de-encapsulates the frame

  • re-encapsulates the packet into a new frame

  • forwards the new fram on the medium

DATA LINK LAYER STANDARDS

• these protocols are defined by engineering organizations:

  • Institute for Electrical and Electronic Engineers (IEEE)

  • International Telecommunications Union (ITU)

  • International Organizations for Standardization (ISO)

  • American National Standards Institute (ANSI)

Topologies

• arrangement and relationship of the network devices and interconnections between them

Physical and Logical Topologies

• Physical Topology: shows physical connections

• Logical Topology: identifies the virtual connections

WAN Topologies

• Point-to-point: simplest and most common. Consists of a permanent link

• Hub and spoke: similar to star topology

  • central site interconnects branch sites through point-to-point links

• Mesh: provides high availability

  • requires every end system to be connected to every other end system

POINT-TO-POINT WAN TOPOLOGY

• physical point-to-point directly connects 2 nodes

• nodes may not share with other hosts

  • all frames on the media can only travel to or from the 2 nodes

• node1 ←> network/media ←> node2

LAN Topologies

• these are typically interconnected using a star or extended star topology

  • easy to install, very scalable, and easy to troubleshoot

• 2 additional topologies:

  • Bus: all end systems chained together

    • terminated on each end

  • Ring: each are connected to its respective neighbors to form a ring

Half and Full Duplex Communication

• Half-duplex:

  • only allows 1 device to send or receive at a time on a shared medium

  • used on WLANs and legacy bus topologies (with ethernet hubs)

• Full-duplex:

  • allows both devices to simultaneously transmit and receive

  • ethernet switches operate in full-duplex mode

ACCESS CONTROL METHODS

• Contention-based access

  • all nodes operating in half-duplex

    • ex. Carrier sense multiple access with collision detection (CSMA/CD) as used on legacy bus-topology ethernet

    • ex. Carrier sense multiple acces with collision avoidance (CSMA/CA) as used on Wireless LANs

    • CSMA/CD: only one device send or receives at a time

      • uses collision detection process to decide when a devicec can send and what happens if multiple devices send at the same time

      • used by legacy ethernet LANs

        • (CS)senses to see if any other computer is currently transitting a signal -> (MA)anyone can send whenever it becomes quiet -> (CD) stops transmitting if a collision happens, sends a jam signal, waits a random amount of time, and tries again.

      • CSMA/CA:

        • used by IEEE 802.11 WLANS

        • devices receive a time duration to know how long the medium will be unavailable when a collision happens

• Controlled Access

  • deterministic access

    • each node has its own time on the medium

  • used on legacy networks

    • such as Token Ring and ARCNET

Data Link Frame

The Frame

• data is encapsulated by the data link layer with a header and a trailer to form a frame

• data link frame parts

  • header

  • data

  • trailer

• amount of control information carried with in the frame varies according to access control information and logical topology

Frame Fields

• Frame Start and Stop - identifies beginning and end of frame

• Addressing - indicates source and destination nodes

• Type - indentifies encapsulated layer 3 protocol

• Control - flow control services

• Data - contains the frame payload

• Error Detection - determines transmission errors

Layer 2 Addresses

• also referred to as a physical address

• contained in the frame head

• used only for local delivery

• updated by each device

LAN and WAN frames

• the logical topology and physcial media determine the data link protocol used:

  • ethernet - rulebook for wired local networks

    • uses physcal cables to send data between computers and switches in the same building

  • 802.11 Wireless - official engineering name for Wi-Fi

    • rulebook for moving data through the air

  • point-to-point (PPP) - direct digital highway

    • used to connect exactly 2 devices

  • High-level data link control (HDLC) - classic cisco-default protocol

    • used to cleanly package and deliver data

  • frame-relay - older, cost-efficient technology

    • allowed multiple businesses to share a single provider network

MODULE 7 (Ethernet Frames)

Ethernet Frames

ETHERNET ENCAPSULATION

• operates in both the data link layer and the physical layer

• comprises a family of networking technologies

  • defined in the IEEE 802.2 and 802.3 standards

DATA LINK SUBLAYER

To make things easier to manage in the 802 LAN/MAN standards and ethernet, the Data Link layer is split into 2 smaller sublayers:

• LLC Sublayer (Logical Link Control - IEEE 802.2) - places control information inside the frame header

  • identifies which network layer protocol is being used for the frame

• MAC Sublayer (Media Access Control - IEEE 802.3, 802.11, or 802.15) - handles data encapsulation, media access control, and physical layer 2 addressing

MAC SUBLAYER

• responsible for data encapsulation and accessing the media

• Data encapsulation:

  • Ethernet Frame - internal layout structure

  • Addressing - adds souce and destination MACs for NIC-to-NIC delivery on the same LAN

  • Ethernet Error Detection - uses Frame Check Sequence (FCS) trailer for error detection

• Media Access (Traffic control):

  • Legacy ethernet using a bus topology or hubs, is a shared half-duplex medium

  • ethernet LANs of today uses switches that operate in full-duplex

ETHERNET FRAME FIELDS

FRAME SIZES:

• Standard Ethernet frame size: minimum 64 bytes,, maximum 1518 bytes

• Runt Frame / Collision Fragment: under 64 bytes. Automatically dropped (usually collision debris)

• Jumbo/baby giant frame: data payload over 1500 bytes (total over 1518 bytes). supported by most fast/gigabit swtiches

• Dropping: any frame outside the 64-1518 byte limits is considered invalid and dropped

Ethernet MAC Address

MAC ADDRESS AND HEXADECIMAL

FORMAT:

• Structure: 48 bits long, written as 12 hexadecimal digits (6 bytes)

• Hex Conversion: 8 bits (1 byte) ranges from binary 00000000 - 11111111 (00 to FF in hex)

• leading zeros are required (0A). Hex is shown in documentation with a 0x prefix (e.g., 0×73), a subscript 16 (7316), or an H suffix (73H)

• MAC addresses provides a method for device identification at the data link layer of the OSI model

• Organizationally Unique Identifier (OUI): assigned to vendors by the IEEE

  • every MAC must be globally unique

  • vendors that sell ethernet devices must register with the IEEE to obtain a unique 6 hexadecimal code

  • consists of 6 hexadecimal vendor OUI code

    • followed by a 6 hexadecimal vendor-assigned value

FRAME PROCESSING

• NIC Filter: A network card checks the Destination MAC of a frame:

  • No match: drops the frame

  • match: pulls it into RAM and de-encapsulates it up the OSI layers

    • NICs also accept frames if the target is a network broadcast or a multicast group they belong to. (PC, routers, printers, and phones all have MACs)

COMMUNICATION TYPES

• Finding destination MACs:

  • IPv4: uses ARP (Adress Resolution Protocol)

    • acts like a public loudspeaker on a local network; it sends a broadcast message to every single device asking, "Who has this IP address, and what is your MAC address?"

  • IPv6: uses ND (Neighbor Discovery)

    • replaces this with a much quieter, targeted multicast message that is delivered only to the specific device in question

• Router Boundary: routers block broadcasts/multicasts by default

  • switches flood them out all ports

The MAC Address Table

SWITCH FUNDAMENTALS

• Layer 2 Rules: switches make decisions based solely on layer 2 MAC addresses.

  • they ignore layer 3 protocols

• CAM (Content Addressable Memory) Table: the MAC Address table or CAM table maps MACs to physical ports

• Boot State: completely empty when powered on

SWITCH LEARNING AND FORWARDING

• Learn (Examine the source MAC adrress)

  • the switch looks at the source mac and the incoming port

  • New MAC: Adds the MAC and port to the table

  • Existing MAC: refreshes its 5-minute aging timer

  • Moved Port: replaces the old record with the new port number

• Forward (Find the Destination MAC Address)

  • Known Unicast: MAC is in the table. sends it out only that one specific port (filtering)

  • Unknown Unicast: Unicast MAC is not in the table. Floods it out all ports except the incoming one

  • Broadcast/Multicast: flooded out all ports except the incoming one automatically

FILTERING FRAMES

• as a switch receives frames from different devices, it is able to populate its MAC address table

  • examines the source MAC address of every frame

Switch Speeds and Forwarding Methods

FRAME FORWARDING METHODS ON CISCO SWITCHES

• Store-and-forward switching: receives the entire frame and checks the CRC code for errors

  • drops bad frames and forwards clean ones

  • Mandatory Quality of Service (QoS): prioritizes traffic (like VoIP over web browsing)

• Cut-Through Switching: reads just the Destination MAC at the front, then immediately starts forwarding

  • no error checking

  • Fast-forward switching: standard method, lowest latency, sends everything instantly, even if broken

  • Fragment-Free switching: stores and checks the first 64 bytes (where most collision happens) before forwarding

MEMORY BUFFERING ON SWITCHES

• an ethernet switch may use a buffering technique to store frames before forwarding them or when the destination port is busy because of congestion

• Port-Based Memory: Frames wait in queues tied to specifc ports

  • can cause Head-of-Line Blocking

• Shared Memory: all frames go into a common pool shared by all ports

  • deposits all frames into a common memory buffer shared by all switch ports

  • amount of buffer memory required by a port is dynamically allocated

  • eliminates line blocking and allows asymmetric switching

DUPLEX AND SPEED SETTINGS

• 2 of the most basic settings on a switch are the bandwitdth

• it’s important that the duplex and bandwidth settings match between the switch port and the connected devices

• Full Duplex: both ends of the connection can send and receive simultaneously

  • two-way talk

  • gigabit ethernet only operates in full-duplex

• Half-Duplex: one side talks at a time (shared media)

  • only one end of the connection can send at a time

• Autonegotiation is an optional function found on most Ethernet switches and NICs

  • enables 2 devices to automatically negotiate the best speed and duplex capabilities

• Duplex Mismatch: performance bug where one side is set to half-duplex and the other to full-duplex

  • fixed by keeping autonegotiation ON/OFF on both sides

• Auto-MDIX: automatically detects the connected cable type (straight-through or crossover)

  • enabled by default on Cisco IOS 12.2(18(SE) or later

  • turn back on using command: Switch(config-if)# mdix auto

MODULE 8 (Network Layer)

Network Layer Characteristics

Network layer

• provides services to allow end devices to exchange data

• IPv4 and IPv6 are the principle network layer communication protocols

• makes communication between different networks possible

• 4 basic operations:

  • addressing end devices

    • assigns logical addresses to devices

  • encapsulation

    • process of adding protocol information to data

    • add layer 3 header

  • routing

    • determines the best path for packets

  • de-encapsulation

    • removes the layer 3 header at the destination

    • passes the data to the transport layer

    • moves up the OSI model

IP ENCAPSULATION

• IP encapsulates the transport layer segment

  • segment becomes the payload of the IP packet

    • segment - PDU of the transport layer

    • payload - actual data carried inside a packet

• IP can use either an IPv4 or IPv6 packet and not impact the layer 4 segment

  • TCP and UDP work with both IPv4 and IPv6

• IP packet will be examined by all layer 3 devices as it traverses the network

  • routers inspect the packet header

  • routers check destination IP addresses

    • traverse - move across a network

this is AI now

• The IP addressing does not change from source to destination.

  • Source and destination IP addresses remain the same during transmission.

Note:

• NAT will change addressing, but will be discussed in a later module.

Definition:

• NAT (Network Address Translation) – modifies IP addresses between private and public networks.

Characteristics of IP

• IP is meant to have low overhead and may be described as:

  • Connectionless

  • Best Effort

  • Media Independent

Definition:

• Overhead – additional processing or control information added during communication.

Connectionless

IP is Connectionless

• IP does not establish a connection with the destination before sending the packet.

  • Packets are sent immediately without setup.

Definition:

• Connectionless Communication – communication without first establishing a dedicated session.

• There is no control information needed (synchronizations, acknowledgments, etc.).

  • IP does not coordinate transmission before sending data.

Definition:

• Synchronization – coordination between devices before communication.

• Acknowledgment (ACK) – a confirmation that data was received.

• The destination will receive the packet when it arrives, but no pre-notifications are sent by IP.

  • IP does not notify the receiver beforehand.

• If there is a need for connection-oriented traffic, then another protocol will handle this (typically TCP at the transport layer).

  • TCP handles reliable communication.

Definition:

• Connection-Oriented Communication – communication requiring an established connection before transmission.

• TCP (Transmission Control Protocol) – reliable transport layer protocol.

Best Effort

IP is Best Effort

• IP will not guarantee delivery of the packet.

  • Packets may be lost during transmission.

Definition:

• Best Effort Delivery – a delivery method without guaranteed success.

• IP has reduced overhead since there is no mechanism to resend data that is not received.

  • Less processing improves transmission speed.

• IP does not expect acknowledgments.

  • IP sends packets without waiting for confirmation

• IP does not know if the other device is operational or if it received the packet.

  • IP cannot detect device status or successful reception.

Definition:

• Operational – functioning and available for communication.

Media Independent

IP is unreliable

• It cannot manage or fix undelivered or corrupt packets.

  • IP does not repair damaged packets.

Definition:

• Corrupt Packet – a packet damaged during transmission.

• IP cannot retransmit after an error.

  • Lost packets are not resent by IP.

Definition:

• Retransmission – sending data again after failure.

• IP cannot realign out of sequence packets.

  • IP cannot reorder packets arriving incorrectly.

Definition:

• Out-of-Sequence Packets – packets arriving in the wrong order.

• IP must rely on other protocols for these functions.

  • TCP commonly handles reliability.

IP is Media Independent

• IP does not concern itself with the type of frame required at the data link layer or the media type at the physical layer.

  • IP works regardless of the network technology used.

Definition:

• Data Link Layer – Layer 2 responsible for framing and MAC addressing.

• Physical Layer – Layer 1 responsible for physical transmission.

• Frame – the PDU of the data link layer.

• IP can be sent over any media type:

  • copper

  • fiber

  • wireless

Definition:

• Media Type – the physical method used to transmit signals.

Media Independent (Contd.)

Maximum Transmission Unit (MTU)

• The network layer will establish the Maximum Transmission Unit (MTU).

Definition:

• MTU (Maximum Transmission Unit) – the largest packet size allowed on a network.

• Network layer receives this from control information sent by the data link layer.

  • Layer 2 informs Layer 3 about size limitations.

• The network then establishes the MTU size.

  • Devices determine the largest allowable transmission size.

Example:

• Ethernet MTU = 1500 bytes

Definition:

• Byte – 8 bits.

Fragmentation

• Fragmentation is when Layer 3 splits the IPv4 packet into smaller units.

Definition:

• Fragmentation – dividing packets into smaller pieces to fit MTU limitations.

• Fragmenting causes latency.

  • Extra processing increases delay.

Definition:

• Latency – delay in data transmission.

• IPv6 does not fragment packets.

  • Routers do not perform fragmentation in IPv6.

• Example: Router goes from Ethernet to a slow WAN with a smaller MTU.

  • Large packets may not fit the WAN packet size limit.

Definition:

• WAN (Wide Area Network) – a network covering large geographic distances.

8.2 IPv4 Packet

IPv4 Packet Header

• IPv4 is the primary communication protocol for the network layer.

  • Widely used for internet communication.

Purposes of the Network Header

• It ensures the packet is sent in the correct direction (to the destination).

  • Routers use destination addresses for forwarding.

• It contains information for network layer processing in various fields.

  • Header fields contain routing and control information.

Definition:

• Header Field – a section containing specific protocol information.

• The information in the header is used by all Layer 3 devices that handle the packet.

  • Routers process packet headers while forwarding traffic.

IPv4 Packet Header Fields

Characteristics of the IPv4 Header

• It is in binary.

  • Information is represented using 0s and 1s.

Definition:

• Binary – numbering system using only two digits: 0 and 1.

• Contains several fields of information.

  • Each field performs a specific networking function.

• Diagram is read from left to right, 4 bytes per line.

  • Packet diagrams are structured systematically.

• The two most important fields are the source and destination.

  • Identifies sender and receiver IP addresses.

• Protocols may have one or more functions.

  • Protocols can perform multiple communication tasks.

Significant Fields in the IPv4 Header

Version

• This will be for v4, as opposed to v6, a 4-bit field =

010001000100

• Identifies the IP version used in the packet.

Differentiated Services

• Used for QoS: DiffServ – DS field or the older IntServ – ToS or Type of Service.

  • Prioritizes important traffic.

Definition:

• QoS (Quality of Service) – prioritization of network traffic.

• DiffServ – Differentiated Services method for QoS.

• ToS (Type of Service) – older QoS mechanism.

Header Checksum

• Detect corruption in the IPv4 header.

  • Verifies header integrity.

Definition:

• Checksum – a value used to detect transmission errors.

Time to Live (TTL)

• Layer 3 hop count.

  • Each router decreases TTL by 1.

Definition:

• Hop – movement from one router to another.

• When it becomes zero the router will discard the packet.

  • Prevents endless routing loops.

Definition:

• Routing Loop – packets endlessly circulating between routers.

Protocol

• I.D.s next level protocol:

  • ICMP

  • TCP

  • UDP

Definition:

• ICMP (Internet Control Message Protocol) – used for diagnostics and error reporting.

• UDP (User Datagram Protocol) – fast connectionless transport protocol.

Source IPv4 Address

• 32-bit source address.

  • Identifies the sender device.

Destination IPv4 Address

• 32-bit destination address.

  • Identifies the receiving device.