AECSC Task 1 Cheatsheet

09/11/2025

The Ultimate Networking Cheatsheet

Part 1: Core Concepts & Definitions

This section covers the foundational knowledge. Memorize these definitions and examples.

1.1 Network Security

Network Security: The practice of protecting data and systems from unauthorised access, misuse, or damage. Its goal is to protect against identity theft, data breaches, and service disruptions. [1]
- Example: A school network protecting student records from being accessed by outsiders. [1]
Need for Preventing Unauthorised Access: To protect confidential information, maintain system integrity (prevent tampering/malware), and ensure system availability (keep services online). [1]
- Example: Preventing a hacker from breaching a hospital system to steal patient data. [1]
Key Security Methods:
- Authentication: Verifying a user’s identity (e.g., passwords, biometrics, 2FA). [1]
- Encryption: Scrambling data to make it unreadable to unauthorised parties. [1]
- Firewalls: Monitoring and filtering network traffic based on security rules. [1]
- Regular Updates: Patching software vulnerabilities to prevent attacks. [1]

1.2 Network Performance

Bandwidth: The maximum amount of data that can be transmitted over a network in a given time, measured in Mbps or Gbps. Think of it as the width of a highway. [2, 8]
- Factors Affecting Bandwidth: Network infrastructure (fibre vs. copper), traffic congestion, and your ISP plan. [2]
Throughput: The actual amount of data successfully transmitted, which is often less than the total bandwidth due to latency and packet loss. [2]
Latency: The time it takes for data to travel from source to destination (the delay), measured in milliseconds (ms). High bandwidth does not guarantee low latency. [2]
Collision Domain: A network segment where data packets can “collide” if sent simultaneously by multiple devices. Collisions force retransmissions, slowing the network. Hubs create a single large collision domain. [2]
- Modern Solution: Switches largely eliminate this problem by giving each port its own collision domain. [2]
Network Segmentation: Dividing a large network into smaller, isolated segments using switches and routers. This reduces the size of collision domains and broadcast traffic, improving performance and security. [2]
Subnetting: The process of dividing a larger IP network into smaller subnetworks (subnets). It operates at Layer 3 and improves performance, security, and IP address management. Each subnet is its own broadcast and collision domain. [2, 7]

1.3 Network Topologies

The physical or logical arrangement of devices on a network. [2, 8]

Topology	Description	Advantages	Disadvantages	Use Case
Star	All devices connect to a central hub/switch. [2]	Easy to manage; one device failure doesn’t affect others. [2]	If the central hub fails, the whole network fails. [2]	Home networks, small businesses. [2]
Bus	All devices share a single communication line. [2]	Cheap and simple to set up. [2]	Performance degrades as more devices are added; a failure in the main cable shuts down the network. [2]	Small, temporary, low-traffic networks. [2]
Ring	Devices are connected in a circle, with data flowing in one direction. [2]	Reduces packet collisions. [2]	If one device fails, the whole ring can fail. [2]	LANs where structured data flow is needed. [2]
Mesh	Every device is connected to every other device (fully) or multiple other devices (partially). [2]	Extremely redundant and fault-tolerant; excellent performance. [2]	Very expensive and complex to set up. [2]	Data centers, critical enterprise networks. [2]
Hybrid	A combination of two or more topologies (e.g., Star-Bus). [2]	Flexible, scalable, and allows performance optimization. [2]	Can be complex and expensive.	Large organizations, universities. [2]

Part 2: The DoD (TCP/IP) Model

This 4-layer model is the blueprint for all internet communication. TCP/IP stands for Transmission Control Protocol/Internet Protocol. [3, 8]

Layer	Role & Function	Key Protocols	Real-World Example
4. Application	”Where users meet the network.” Provides services for user applications. It’s not the app itself, but the protocols that let apps talk over the network (data formatting, initiating communication). [3]	HTTP/HTTPS (web), SMTP (email), FTP (files), DNS (domain names). [3]	Your browser using HTTP to fetch a webpage from a web server. [3]
3. Transport	”The delivery department.” Provides reliable, end-to-end data delivery between devices. It breaks data into segments, handles error checking, and uses port numbers to direct data to the right app. [3]	TCP (reliable, connection-oriented), UDP (fast, connectionless). [3]	When streaming a video, TCP ensures all data packets arrive in the correct order so the video plays without corruption. [3]
2. Internet	”The routing department.” Responsible for routing packets across different networks. It adds source and destination IP addresses and finds the best path for data to travel. [3]	IP (IPv4/IPv6) (addressing/routing), ICMP (errors, e.g., ping), ARP (maps IP to MAC). [3]	When you send an email from Perth to London, routers use the IP address on each packet to forward it across the globe. [3]
1. Network Access	”The physical workers.” Handles the physical transmission of data (frames) over the network medium (cables, Wi-Fi). It converts data into signals (electrical, radio, light) and uses MAC addresses for local delivery. [3]	Ethernet (wired), Wi-Fi (wireless), MAC (hardware address). [3]	Your laptop’s Wi-Fi card converting a data frame into radio waves to send to the wireless router. [3]

Part 3: Network Components & Addressing

3.1 Key Hardware Components

Component	Function	TCP/IP Layer
Modem	Connects your network to the internet by modulating/demodulating signals between the digital data of a computer and the analog signal of the ISP line. [8]	Layer 1 (Network Access / Physical) [6]
Router	Connects multiple networks and forwards data packets between them based on IP addresses. Acts as the default gateway for devices to reach outside networks. [8]	Layer 2 (Internet) [6]
Switch	Connects devices within a single LAN and forwards data frames only to the specific device with the matching MAC address. It breaks up collision domains. [8]	Layer 1 (Network Access) [4]
Wireless Access Point (WAP)	Allows wireless devices to connect to a wired network. It broadcasts a Wi-Fi signal to extend network coverage. [8]	Layer 1 (Network Access) [6]
Firewall	A security device that monitors and filters incoming and outgoing traffic based on security rules to block threats and unauthorised access. [8]	Operates across multiple layers, primarily Layer 3 (Internet) & 4 (Transport). [3]

3.2 IP Addressing & Subnetting

IP Address: A unique numerical label assigned to every device on a network, used for identification and location addressing. It has a Network ID (like a suburb) and a Host ID (like a house number). [3]
- Example: 192.168.1.15.
Subnet Mask: A 32-bit number that splits an IP address into its network and host portions. It helps a router determine if a destination is on the local network or a remote one. [3]
- Example: IP 192.168.1.25 with mask 255.255.255.0 means the Network ID is 192.168.1 and the Host ID is 25. [3]
Default Gateway: The IP address of the router that a device sends packets to when the destination is outside the local network. It’s the “exit door” for all external traffic. [8]
IPv4 vs. IPv6:
- IPv4: 32-bit addresses (~4.3 billion total).
- IPv6: 128-bit addresses (a virtually limitless number). This solves the address exhaustion problem of IPv4. [6]
- Other IPv6 Advantages: Simplified header for faster routing, no need for NAT, and built-in security (IPsec). These are standard concepts your test might ask about. [6]

Part 4: The Flawless Exam Q&A Guide

Here are complete, A-grade answers to all the past exam questions.

Network Design & Diagram Questions

Drawing Network Diagrams (General Approach for Q5-2023, Q3-2024, Q6-2025)

Since you can’t draw in a text-based format, here is the exact procedure to get full marks by describing the connections with CISCO icons (as listed in your notes [8]).

Internet -> Modem -> Firewall -> Router: Start with the Cloud icon for the Internet. Connect it to a Modem icon. Connect the Modem to a Firewall icon. Connect the Firewall to the central Router icon. This is your network’s main entry point.
Create Segments: For each department (e.g., Sales, Developers, Servers), connect a Switch icon to the central Router. This creates separate network segments.
Connect Devices:
- Connect Desktop computer icons and Network Printer icons to their department’s Switch using straight lines (for UTP).
- For wireless access, connect a Wireless Access Point (WAP) icon to the department’s Switch.
- Connect Notebook/Laptop and Mobile phone icons to the WAP using wireless signal lines.
Label Everything: Clearly label each icon (e.g., “Sales Switch,” “Developer PC 1”) and each network segment.

Question 3 (2023 Exam - Laser Arena) [6]

Diagram Description:
1. Start with Cloud (Internet) -> Modem -> Firewall -> Router.
2. From the Router, create three segments by connecting to three separate Switches: “Café Switch,” “Game Area Switch,” and “Accounts Office Switch.”
3. Café Segment: Connect a WAP to the “Café Switch” for customer Wi-Fi.
4. Game Area Segment: Connect a WAP to the “Game Area Switch.” Show a Laptop and a Server (“Game Server”) also connected to this switch. The WAP provides connectivity for the 30 vests (you don’t need to draw 30 devices, just note the WAP serves them).
5. Accounts Office Segment: Connect 2 Desktop computers, 1 Printer, and 1 Server (“Business Server”) to the “Accounts Office Switch.”
Function of Components:
- Router: Forwards data packets between the different network segments (Café, Game Area, Accounts) and to the internet. [8]
- Switch: Connects devices within a single segment (e.g., all the devices in the Accounts Office) and forwards traffic intelligently using MAC addresses. [8]
- Wireless Access Point: Provides wireless connectivity for devices like customer phones in the café and the gaming vests. [8]

TCP/IP Model Questions

Question 3 (2023 Exam): Complete the Table [6]

Application:
- Description: Provides an interface for user applications to access network services. [3]
- Protocol: DNS, FTP, HTTP.
Transport:
- Layer Name: Transport.
- Description: Provides a reliable data connection, divides data into packets (segments), responsible for acknowledgement from recipient and sender. [3]
- Protocol: TCP, UDP.
Internet:
- Description: Responsible for logical addressing (IP addresses) and routing packets across different networks. [3]
- Protocol: IP, ARP.
Network Access:
- Layer Name: Network Access.
- Description: Handles the physical infrastructure connecting devices on a network. [3]
- Protocol: Ethernet, Wi-Fi.

Question 2 (2024 Exam): TCP/IP Layers & Protocols [6]

Expand Acronym: Transmission Control Protocol/Internet Protocol.
Purpose of Layers:
- Application layer: Provides network services directly to user applications, such as web browsing (HTTP) and email (SMTP). [3]
- Transport layer: Ensures reliable end-to-end data delivery, managing flow control and error checking using protocols like TCP. [3]
- Internet layer: Handles the addressing and routing of data packets across networks using IP addresses to determine the best path. [3]
Key Protocols:
- Application layer protocol: HTTP (or DNS, FTP, SMTP).
- Transport layer protocol: TCP (or UDP).
- Internet layer protocol: IP (or ICMP, ARP).

IP Addressing & Subnetting Questions

Question 4 (2024 Exam) / Question 6 (2023 Exam) [6]

Role of Subnet Mask: A subnet mask is used to divide an IP address into two parts: the network portion and the host portion. This allows routers to efficiently determine whether a packet is for a device on the local network or if it needs to be sent to a remote network via the default gateway. [3, 7]
Purpose of Default Gateway: The default gateway is the router on a local network that acts as the exit point for all traffic destined for outside networks (like the internet). When a device needs to send a packet to an external IP, it sends it to the default gateway to be routed. [8]
How many usable IPv4 addresses with 255.255.255.192 mask?
- Number of addresses: 62.
- Justification: The subnet mask 255.255.255.192 uses 26 bits for the network (/26), leaving 32 - 26 = 6 bits for the host portion. The formula for usable hosts is 2^h - 2, where h is the number of host bits. Therefore, 2^6 - 2 = 64 - 2 = 62 usable host addresses. The two subtracted addresses are the network address and the broadcast address.
Provide IP addresses for other segments (Developer/Tester):
- The sales network 192.115.110.64/26 is given. The next available subnets (incrementing by 64) are .128 and .192.
- Developer device:
  - IP address: 192.115.110.129 (a valid host in the .128 subnet).
  - Subnet mask: 255.255.255.192.
- Tester device:
  - IP address: 192.115.110.193 (a valid host in the .192 subnet).
  - Subnet mask: 255.255.255.192.

Network Security Questions

Question 1 (2023 Exam): Role of Firewall & OS [6]

Firewall: A firewall improves network security by monitoring and filtering all incoming and outgoing network traffic. It acts as a barrier, blocking unauthorised connections and malicious packets based on a set of security rules, thereby preventing hackers and malware from accessing the internal network. [1, 8]
Operating system: An OS enhances security by managing user authentication and access control to restrict what users can do. It also delivers regular security updates (patches) to fix vulnerabilities and often includes built-in security tools like firewalls (e.g., Windows Defender) and antivirus capabilities. [1, 8]

Discuss the role of firewalls in securing networks. (2025 Exam) [6]

A firewall is a critical component of network security that acts as a gatekeeper for network traffic. It inspects data packets entering and leaving the network, deciding whether to allow or block them based on predefined security rules. For example, it can block traffic from known malicious IP addresses or prevent internal users from accessing prohibited websites. By filtering harmful traffic and preventing unauthorised access, a firewall serves as the first line of defense against cyber threats like hacking attempts and malware infections. [1, 8]

Network Performance Questions

Question 2 (2023 Exam): Factors affecting performance [6]

Bandwidth: Bandwidth is the maximum data transfer capacity of a network. If the bandwidth is too low for the amount of traffic (e.g., many users streaming video), the network becomes congested, like a traffic jam on a narrow highway. This results in slow speeds and poor performance for all users. [2]
Network design: The topology and structure of the network heavily impact performance. A poor design, like connecting too many devices to a single router or using an outdated topology like a bus network, can create bottlenecks and increase data collisions. Proper segmentation and using modern topologies like star with switches can drastically improve data flow and speed. [2]

Question 3 (2025 Exam): Coastal Shipping Congestion [6]

Reason for slow speeds: Connecting 1000 employees to a single central router creates a massive bottleneck. All traffic from all employees must pass through this one device, overwhelming its processing capacity during peak hours. Furthermore, all 1000 employees are in the same broadcast domain, meaning broadcast traffic (like ARP requests) will be sent to every device, consuming significant bandwidth and slowing down the network.
Improvement: The best improvement is network segmentation. This involves using the central router to connect to several switches, with each switch serving a different department or floor. This breaks the single large network into smaller, more manageable subnets.
- Justification: This improves performance by isolating traffic within each department, reducing the overall load on the router. It also creates smaller broadcast domains, so broadcast traffic no longer floods the entire network of 1000 employees, freeing up bandwidth for essential data transfer.