Wednesday, April 22, 2026
13 min read
Cohort 3 | Project CloudIgnite Topics: Networking Fundamentals & AWS VPC Duration: ~3 hours
🎯 CLF-C02 Relevance: Sections marked with
[CLF-C02]directly map to the AWS Certified Cloud Practitioner exam objectives (Domain 2: Security & Compliance / Domain 3: Cloud Technology & Services — specifically VPC, subnets, security groups, and networking concepts).
Key Takeaways
- OSI Model key layers: L7 (HTTP/HTTPS/FTP/SSH), L4 (TCP/UDP), L3 (IP), L2 (MAC/Switch)
- TCP: connection-oriented, 3-way handshake (SYN→SYN-ACK→ACK), reliable; UDP: connectionless, fast, no guarantee
- Amazon VPC: logically isolated virtual network; public subnets (web servers) vs private subnets (databases)
- Key ports: 22 (SSH), 80 (HTTP), 443 (HTTPS), 53 (DNS), 3389 (RDP)
- Network topologies: bus, star, mesh, hybrid; AWS VPC ≈ logically isolated LAN
- IPv4: 32-bit; IPv6: 128-bit; DHCP auto-assigns IPs; Elastic IP for static public addresses
Table of Contents
- OSI Model
- Network Components
- Network Cables
- Network Types: LAN & WAN
- Network Topologies
- Virtual Private Cloud (VPC)
- Network Management Models
- Network Protocols: TCP & UDP
- Internet Protocol (IP)
- IP Addresses
- Subnetting & CIDR Basics
- Port Numbers
- Binary & Decimal Conversion
- Quick Reference / Cheat Sheet
1. OSI Model
The OSI (Open Systems Interconnection) model is a 7-layer framework for understanding how data travels across a network.
| Layer | Name | Protocols / Notes |
|---|---|---|
| 7 | Application | HTTP, HTTPS, FTP, SFTP, SMTP, SSH |
| 6 | Presentation | Data formatting/encryption |
| 5 | Session | Session management |
| 4 | Transport | TCP, UDP |
| 3 | Network | IP (Internet Protocol) |
| 2 | Data Link | Physical addressing (MAC), Switch operates here |
| 1 | Physical | Cables, NIC, physical signal |
⭐ Key Layers to Remember: 3, 4, and 7
- Layer 3 → IP Protocol
- Layer 4 → TCP / UDP
- Layer 7 → HTTP, HTTPS, FTP, SSH
TCP/IP Model (alternative, simpler model): Only 4 layers. Commonly used in practice, but OSI is preferred for learning.
2. Network Components
| Component | Description |
|---|---|
| Node | Any device on a network — laptop, phone, printer, desktop |
| NIC (Network Interface Card) | Hardware that allows a device to connect to a network; has a unique MAC address; operates on Layer 2 |
| Switch | Connects multiple nodes within the same network (LAN); decides where to forward data using MAC addresses; Layer 2 device |
| Router | Connects multiple networks together; routes traffic between networks; operates on Layer 2–3 |
| Modem | Connects your local network to the internet (ISP or cellular); has two ports — one to internet, one to local device |
Client vs. Server
- Client: Device that sends a request (laptop, phone)
- Server: Device that processes the request and sends a response (web server, database server)
MAC Address
- Unique physical identifier assigned by the manufacturer to every NIC
- Used at Layer 2 for local network communication
- Can be "spoofed" (faked) in software, but the hardware MAC cannot be changed
- Format includes a manufacturer prefix + unique identifier
3. Network Cables
| Cable Type | Description | Use Case |
|---|---|---|
| Fiber Optic | Transmits data as light signals; very fast | Long-distance, high-speed connections |
| Coaxial | Older cable type; previously used for TV/cable (e.g., Astro) | Legacy use |
| Twisted Pair (CAT6/Ethernet) | Standard LAN cable; uses RJ45 connector | Office/home networks, LAN |
- RJ45 = the connector used with twisted pair (CAT6) cables — not the cable itself
4. Network Types: LAN & WAN
LAN — Local Area Network
- Covers a small geographic area: a room, floor, building, campus, or office
- All computers within a building connected via switches; floors connected via routers
- Example: University computer lab network
WAN — Wide Area Network
- Connects multiple cities or countries
- Made up of interconnected LANs
- Example: The internet itself is the largest WAN
AWS Context: A single VPC ≈ LAN; multiple VPCs connected together ≈ WAN
5. Network Topologies
Topology = how devices are physically or logically arranged and connected.
Physical Topologies
| Topology | Description | Notes |
|---|---|---|
| Bus | All nodes connect to a single shared line/cable | Simple but single point of failure |
| Star | All nodes connect individually to a central switch | Most common; switch in the middle |
| Mesh | Every node connects directly to every other node | Full mesh = all connected; Partial mesh = some connections missing |
| Hybrid | Combination (e.g., Star + Bus) | Common in real-world networks |
Logical Topologies
- Not about physical wires — about how data flows through the network
- Examples: Logical Bus (data travels one direction), Logical Star (central switch distributes), Logical Mesh (peer-to-peer paths)
- Repeater: Restores signal strength when it weakens over long distances
💡 VPC Connection: VPC is a logically isolated network — not physically separate hardware, but data is kept logically separated (like different partitions on the same hard disk).
6. Virtual Private Cloud (VPC) [CLF-C02]
CLF-C02 Domain: Cloud Technology & Services — Amazon VPC is a core exam topic.
What is a VPC?
- VPC (Virtual Private Cloud): A logically isolated virtual network within AWS where you launch AWS resources
- Similar to a LAN, but in the cloud
- Logically isolated — may share physical hardware with others, but data/traffic is fully separated
Key VPC Concepts
| Concept | Description |
|---|---|
| Subnet | A subdivision of a VPC; can be public or private |
| Public Subnet | Accessible from the internet; for web servers |
| Private Subnet | Not accessible from the internet; for databases |
| Availability Zone | Physical location within an AWS region where subnets reside |
| CIDR Block | Defines the IP address range for a VPC or subnet (e.g., 10.0.0.0/16) |
| VPC Peering | Connects two VPCs together (like connecting two LANs = WAN) |
| Internet Gateway | Allows public subnet resources to communicate with the internet |
Security in VPC
- Database → must be in a private subnet (no public internet access)
- Web server → should be in a public subnet (internet-accessible)
- If you accidentally launch a web server in a private subnet, users cannot access it
Reserved IP Addresses in a Subnet
AWS reserves 5 IP addresses in every subnet:
- Network address (1st IP)
- VPC router/Internet Gateway (2nd IP)
- DNS (3rd IP)
- Reserved for future use (4th IP)
- Broadcast address (last IP)
Rule: You must create at least one VPC before launching any AWS resource (EC2, etc.)
7. Network Management Models
Client-Server Model
- A central server handles requests from multiple clients
- Example: Streaming service (server) → your phone (client)
- Web servers, database servers
Peer-to-Peer (P2P) Model
- No central server — any node can communicate directly with any other node
- Example: Torrent file sharing, LAN gaming, distributed computing
- Key application: Distributed systems (splitting tasks across multiple computers)
- Example: Split a large image → send parts to multiple computers → each processes its part → combine results
8. Network Protocols: TCP & UDP
Both operate at Layer 4 (Transport Layer).
TCP — Transmission Control Protocol (Connection-Oriented)
- Establishes a connection before sending data
- Uses 3-Way Handshake:
- SYN — Sender sends synchronize signal ("Are you available?")
- SYN-ACK — Receiver acknowledges and replies ("Yes, I'm ready")
- ACK — Sender confirms ("Let's communicate")
- Reliable: Guarantees data delivery; missing packets are re-sent
- Graceful Termination: FIN → FIN-ACK → ACK (connection closed cleanly)
- RST Signal: Sent when connection is abruptly terminated (e.g., network error)
- Tools to trace TCP packets: Wireshark, tcpdump
- Examples: SSH, HTTPS, email
- SSH uses TCP under the hood even though it appears at Layer 7
UDP — User Datagram Protocol (Connectionless)
- No handshake, no acknowledgement — just sends data
- Faster than TCP (no overhead)
- Not reliable — no guarantee data arrives
- Use cases: live video streaming, YouTube, Zoom/video calls, LAN gaming, DNS lookups
When to use which?
| Use Case | Protocol |
|---|---|
| File transfer, banking, email | TCP |
| Live streaming, video calls | UDP |
| Online gaming (LAN) | UDP |
| Loading a webpage | TCP |
9. Internet Protocol (IP)
- Operates at Layer 3 (Network Layer)
- Defines rules for how data is routed across the internet from one device to another
- Every network device must have an IP address
IP Protocol Rules (Examples)
- Packet size limit — oversized packets are split into smaller packets
- Every device must have an IP address
- Routing algorithm determines which path packets take
- TTL (Time to Live): Maximum time a packet can travel; dropped if TTL expires
IPv4 vs IPv6
| Feature | IPv4 | IPv6 |
|---|---|---|
| Bits | 32-bit | 128-bit |
| Format | 192.168.1.1 (4 octets, 0–255 each) | Long hexadecimal string |
| Max devices | ~4.3 billion | Trillions |
| Speed/Security | Standard | Faster & more secure |
| Status | Still dominant | Slowly being adopted |
Why still on IPv4? Legacy devices and applications don't support IPv6. Transition is gradual.
10. IP Addresses
Public vs Private IP
| Type | Description | Access |
|---|---|---|
| Public IP | Globally unique; routable on the internet | Anyone with internet can reach it |
| Private IP | Only accessible within the local network | Not reachable from outside |
- RFC 1918 defines the standard private IP ranges
- DHCP (Dynamic Host Configuration Protocol): Automatically assigns IP addresses when devices connect to a router
- Static IP: Manually configured; does not change — required for servers and printers
IP Address Structure (IPv4)
- 32 bits = 4 octets, each ranging from 0–255
- Example:
192.168.165.x - Each IP has two parts: Network portion + Host portion
- Which bits are network vs host is determined by the subnet mask
AWS EC2 IP Assignment
- Private IP is always assigned when launching an EC2 instance
- Public IP is optional (you choose whether to assign one)
- For servers, use static (Elastic) IP so the address doesn't change on restart
11. Subnetting & CIDR Basics
CIDR (Classless Inter-Domain Routing)
- Notation:
10.0.0.0/16— the/16tells you how many bits are the network portion - More bits for network = fewer bits for hosts = smaller subnet
How many hosts per subnet?
- Formula: 2ⁿ total addresses (where n = number of host bits)
- Usable hosts = 2ⁿ − 5 (AWS reserves 5 addresses per subnet)
Broadcast Address
- Always the last IP in a range; ends in
.255 - Sending to broadcast delivers the message to all devices in the network
💡 Use an online subnet calculator for exam labs — you don't need to calculate manually!
12. Port Numbers [CLF-C02]
CLF-C02 Relevance: Security groups in AWS control traffic by port. Knowing key ports is essential for troubleshooting and exam questions.
Ports are logical endpoints (like doors) on a device. IP address finds the device; port number finds the service.
Key Ports to Memorize
| Port | Protocol/Service | Notes |
|---|---|---|
| 22 | SSH / SFTP | Connect to EC2 instance |
| 80 | HTTP | Web traffic (unencrypted) |
| 443 | HTTPS | Web traffic (encrypted) |
| 20/21 | FTP | File transfer |
| 53 | DNS | Domain name resolution |
| 3389 | RDP | Windows Remote Desktop (rarely used in AWS/Linux) |
Troubleshooting with Ports [CLF-C02]
- Can't SSH into EC2? → Check Security Group for port 22
- Web server not reachable (HTTP)? → Check Security Group for port 80
- Web server not reachable (HTTPS)? → Check Security Group for port 443
Security Group = Firewall in AWS — controls inbound/outbound traffic by port
13. Binary & Decimal Conversion
Note: Instructor mentioned this is unlikely to appear directly in AWS exams, but useful for understanding subnetting.
Decimal → Binary
Express the number as sums of powers of 2, then assign 1 (if bit used) or 0 (if not).
Example: Convert 21 to binary
- 21 = 16 + 4 + 1 = 2⁴ + 2² + 2⁰
- Bit positions (7 to 0):
0 0 0 1 0 1 0 1= 00010101
Binary → Decimal
Multiply each bit by its positional power of 2, sum the results.
Example: 10101010
- = 128 + 0 + 32 + 0 + 8 + 0 + 2 + 0 = 170
💡 Use online tools: subnet calculators, binary converters — no need to do this manually in exams or labs.
14. Quick Reference / Cheat Sheet
OSI Layers (Must Know)
Layer 7 → HTTP, HTTPS, FTP, SSH
Layer 4 → TCP (reliable), UDP (fast)
Layer 3 → IP (routing)
Layer 2 → MAC address, Switch
Layer 1 → Physical cables, NIC
Key Protocols Summary
| Protocol | Layer | Type | Reliable? |
|---|---|---|---|
| HTTP/HTTPS | 7 | App | N/A |
| SSH | 7 (uses TCP) | App | Yes |
| TCP | 4 | Transport | ✅ Yes |
| UDP | 4 | Transport | ❌ No |
| IP | 3 | Network | N/A |
Port Numbers (Memorize These)
22 → SSH / SFTP
53 → DNS
80 → HTTP
443 → HTTPS
20/21 → FTP
3389 → RDP (Windows)
VPC Essentials (CLF-C02)
VPC = Logically isolated virtual network in AWS
Subnet = Subdivision of a VPC (public or private)
Public Subnet = Web servers, internet-facing
Private Subnet = Databases, internal services
Security Group = Virtual firewall (controls port access)
Internet Gateway = Allows internet access for public subnet
CIDR Block = IP range for VPC/subnet (e.g., 10.0.0.0/16)
AWS reserved IPs = 5 per subnet (cannot be used for instances)
🎯 CLF-C02 Exam Relevance Summary
The following topics from this lecture are directly relevant to the AWS Certified Cloud Practitioner (CLF-C02) exam:
| Topic | CLF-C02 Domain | Importance |
|---|---|---|
| Amazon VPC — what it is, public/private subnets | Domain 3: Cloud Technology | ⭐⭐⭐ High |
| Security Groups — port-based firewall rules | Domain 2: Security & Compliance | ⭐⭐⭐ High |
| Public vs. Private IP addresses | Domain 3: Cloud Technology | ⭐⭐⭐ High |
| Subnets — public for web, private for DB | Domain 3: Cloud Technology | ⭐⭐⭐ High |
| Key Port Numbers (22, 80, 443, 53) | Domain 2: Security & Compliance | ⭐⭐⭐ High |
| Internet Gateway | Domain 3: Cloud Technology | ⭐⭐ Medium |
| TCP vs. UDP (conceptual understanding) | Domain 3: Cloud Technology | ⭐⭐ Medium |
| IPv4 vs. IPv6 (awareness) | Domain 3: Cloud Technology | ⭐ Low |
| OSI Model layers (3, 4, 7) | Foundational knowledge | ⭐ Low |
| LAN/WAN/Topology | Foundational only | ❌ Not directly tested |
📌 Focus for CLF-C02: VPC architecture, subnets (public vs private), security groups, and port numbers are the most exam-relevant topics from this lecture. The networking fundamentals (OSI, TCP/UDP, LAN/WAN) are background knowledge that supports understanding — not directly tested on the Cloud Practitioner exam.
📅 Next Session
- Labs: 261 and 262 (Networking in AWS)
- Topic: Networking in AWS Cloud / Amazon VPC
- Activity: Create subnets in AWS, configure VPC settings
Notes compiled from lecture — April 22, 2026