In-Depth Notes on Network Engineering Course

Introduction to Network Devices

  • Course Development: Developed by Brian Farrell of Edmonds College.
  • Purpose: Configure, manage, and troubleshoot computer networks, preparing for CompTIA's Network+ exam.

OSI Model Overview

  • Open Systems Interconnection (OSI) Model: Developed to help diverse computing systems communicate.
  • Seven Layers of OSI Model:
    1. Physical Layer (Layer 1) - Transmits raw data.
    2. Data Link Layer (Layer 2) - Handles node-to-node data transfer and error correction.
    3. Network Layer (Layer 3) - Manages device addressing and path selection.
    4. Transport Layer (Layer 4) - Ensures complete data transfer.
    5. Session Layer (Layer 5) - Manages sessions between applications.
    6. Presentation Layer (Layer 6) - Translates data format.
    7. Application Layer (Layer 7) - Interface for applications.

Layer 1 Devices

1. Modems
  • Definition: Modulator-demodulator that converts digital signals to analog and vice versa.
  • Functionality: Connect digital devices to an analog medium (like a telephone line).
  • OSI Layer: Primarily operates at Layer 1.
2. Hubs
  • Function: Acts as a repeater; receives data on one port and broadcasts it to all others.
  • Modern Usage: Rarely used due to inefficiencies compared to switches.
  • OSI Layer: Operates at Layer 1.

Layer 2 Devices

1. Switches
  • Functionality: Uses MAC addresses to direct traffic specifically to a device.
  • Types: Vary from simple (few ports) to complex programmable switches.
  • Communication Scope: Only local devices.
  • OSI Layer: Operates at Layer 2.
2. Wireless Access Points (WAP)
  • Function: Connects wired and wireless segments of a network (e.g., bridges Ethernet and WiFi).
  • Typical Standards: Often connect 802.11 (WiFi) with 802.3 (Ethernet).
  • OSI Layer: Operates at Layer 2.

Layer 3 Devices

1. Multilayer Switches
  • Functionality: Performs Layer 2 switching and Layer 3 routing.
  • Price Point: Generally high; used in enterprise environments.
  • Communication Scope: Can connect local to non-local devices.
  • OSI Layer: Primarily operates at Layer 3.
2. Routers
  • Functionality: Routes data between different networks based on IP address.
  • Decision Making: Uses software to track networks and determine best routes.
  • Communication Scope: Can route data to both local and non-local devices.
  • OSI Layer: Operates at Layer 3.

Security Devices (Part 1)

1. Firewalls
  • Functionality: Monitors and controls incoming/outgoing network traffic.
  • Methods: Stateless and stateful inspection to filter packets.
  • OSI Layers: Operates across Layers 2, 3, 4, and 7.
  • First Line of Defense: Protects internal networks against outside threats.

Security Devices (Part 2)

2. Intrusion Detection System (IDS)
  • Functionality: Passive monitoring that identifies potential threats against the network.
  • Alert Mechanisms: Informs admins via logs, messages, or emails.
  • Deployment Types: Host-based (HIDS) or Network-based (NIDS).
3. Intrusion Prevention System (IPS)
  • Functionality: Activates countermeasures against perceived threats in real-time.
  • Active Response: Can block IPs, terminate sessions, or redirect attacks.
  • Network Placement: Ideally positioned between the firewall and internal networks.

Virtual Private Networks (VPN)

1. Definition
  • Purpose: Extends a private network across a public network using encrypted tunnels.
  • Remote Access: Allows external devices to act as if they are on the local network.
2. Types of VPNs
  • Site-to-Site: Connects entire networks, managed via VPN concentrators.
  • Remote Access VPN: Secure access for individual users to the local network.
  • Host-to-Host: Creates secure connections between two specific devices.
3. VPN Protocols
  • IPsec: Often used for securing site-to-site and remote access VPNs.
  • PPTP, GRE, TLS/SSL: Other protocols offering various degrees of security and efficiency.

DHCP (Dynamic Host Configuration Protocol)

1. Overview and Function
  • Purpose: Automatically assigns IP addresses and related configuration settings to devices.
  • Static vs Dynamic: Static is manually configured; dynamic is automatically assigned via DHCP.
2. DHCP Process Steps
  • Discovery: Client sends out a Discovery packet.
  • Offer: DHCP server responds with an Offer packet.
  • Request: Client sends a Request packet to accept the offer.
  • Acknowledgment: Server sends back an Acknowledgment packet with configurations.
3. DHCP Components
  • Ports: UDP port 67 for requests, UDP port 68 for server responses.
  • Scopes and Reservations: Defined ranges of IPs for dynamic and fixed addresses.

Domain Name System (DNS)

1. Definition and Purpose
  • Mapping: Translates human-friendly domain names to IP addresses.
  • FQDN: Fully Qualified Domain Name defines specific resources within a domain.
2. Types of DNS Servers
  • Local DNS: Maps local requests.
  • Top-Level Domain (TLD) Servers: Maintains records for TLDs like .com or .org.
  • Authoritative Servers: Answer queries with original records.
3. DNS Records Types
  • A Record: Maps hostname to IPv4 address.
  • AAAA Record: Maps hostname to IPv6 address.
  • CNAME Record: Alias for another domain.
  • MX Record: Routes emails for specified domain.

Network Address Translation (NAT)

1. Purpose
  • Function: Converts private IPs to public IPs for routing on the internet.
  • Static NAT vs Dynamic NAT: Static assigns one-to-one mapping; dynamic allocates from a pool.
2. NAT Terminology
  • Inside Local Address: Private IP of device on internal network.
  • Inside Global Address: Public IP representing an internal device externally.
  • Outside Local/Global Addresses: Represents external devices from the perspective of internal devices.

WAN Technologies

1. Public Switched Telephone Network (PSTN)
  • Types: Dial-up, ISDN, DSL, using PSTN for WAN connectivity.
2. Broadband Cable
  • Delivery: Coaxial networks providing data, voice, and TV.
  • DOCSIS Specifications: Required for modem compatibility.
3. Fiber Optics
  • Transmission: High bandwidth over long distances, less susceptible to noise.
  • Standards: SONET/SDH for transmission rates and multiplexing.

WAN Standards and Technologies

1. Metro Ethernet
  • Description: Ethernet technology extending beyond LAN to cover metropolitan areas.
2. Leased Lines
  • Purpose: Point-to-point connection providing constant bandwidth.
  • Technologies: T-Carriers and E-Carriers for digital signals.
3. Circuit-Switched vs Packet-Switched
  • Differentiation: Circuit involves dedicated channels vs. packet routes data dynamically.

VRF and MPLS Configuration

1. Multi-protocol Label Switching (MPLS)
  • Purpose: Efficiently directs data based on network conditions and application needs.

Network Cabling

1. Twisted Pair Cabling
  • Categories: Cat 5e, Cat 6, Cat 6a for different speeds and distances.
2. Coaxial Cables
  • Types: RG-58, RG-59, RG-6 for various applications.
3. Fiber Optic Cables
  • Types: Single-mode and multimode fibers for long-distance high-speed data transmission.