Networking Fundamentals Lab
OSI Model, TCP/IP, Protocols, and Network Devices
1
The OSI Model
20 minutes
Objective: Understand the 7-layer OSI reference model and identify protocols at each layer.
The Seven Layers
7
Application
HTTP, HTTPS, FTP, SMTP, DNS, SSH, Telnet
6
Presentation
SSL/TLS, JPEG, GIF, ASCII, MPEG
5
Session
NetBIOS, RPC, PPTP
4
Transport
TCP, UDP, Port Numbers
3
Network
IP, ICMP, OSPF, EIGRP, BGP, Routers
2
Data Link
Ethernet, MAC, Switches, VLANs, STP
1
Physical
Cables, Hubs, NIC, Fiber, Wireless
Memory Trick (Top-Down): "All People Seem To Need Data Processing" Memory Trick (Bottom-Up): "Please Do Not Throw Sausage Pizza Away"
OSI vs TCP/IP Model
| OSI Model | TCP/IP Model | Protocols |
|---|---|---|
| Application, Presentation, Session | Application | HTTP, DNS, SMTP |
| Transport | Transport | TCP, UDP |
| Network | Internet | IP, ICMP |
| Data Link, Physical | Network Access | Ethernet, Wi-Fi |
OSI Deep Dive
Tasks- List all 7 OSI layers from memory
- Identify which layer HTTP operates at
- Explain the difference between Layer 2 and Layer 3 devices
- Map 5 common protocols to their OSI layers
2
IP Addressing & Subnetting
30 minutes
Objective: Understand IPv4 addressing, subnet masks, and basic subnetting concepts.
IPv4 Address Classes
| Class | Range | Default Mask | Purpose |
|---|---|---|---|
| A | 1.0.0.0 - 126.255.255.255 | /8 (255.0.0.0) | Large networks |
| B | 128.0.0.0 - 191.255.255.255 | /16 (255.255.0.0) | Medium networks |
| C | 192.0.0.0 - 223.255.255.255 | /24 (255.255.255.0) | Small networks |
| D | 224.0.0.0 - 239.255.255.255 | N/A | Multicast |
| E | 240.0.0.0 - 255.255.255.255 | N/A | Reserved |
Private IP Ranges (RFC 1918)
Class A Private
10.0.0.0 - 10.255.255.255 (10.0.0.0/8) -- 16 million addresses
Class B Private
172.16.0.0 - 172.31.255.255 (172.16.0.0/12) -- 1 million addresses
Class C Private
192.168.0.0 - 192.168.255.255 (192.168.0.0/16) -- 65,000 addresses
Subnet Quick Reference
| CIDR | Subnet Mask | Hosts | Use Case |
|---|---|---|---|
| /30 | 255.255.255.252 | 2 | Point-to-point links |
| /28 | 255.255.255.240 | 14 | Small departments |
| /24 | 255.255.255.0 | 254 | Standard LAN |
| /16 | 255.255.0.0 | 65,534 | Large campus |
Host Formula: 2^n - 2 where n = number of host bits. We subtract 2 for network and broadcast addresses.
Tasks- Identify the class of 172.16.5.1
- Calculate how many hosts fit in a /26 network
- Convert 192.168.1.0/24 to binary
- Identify the network and broadcast address for 10.0.5.100/24
3
Transport Layer: TCP vs UDP
20 minutes
Objective: Compare TCP and UDP protocols and understand when to use each.
Protocol Comparison
| Feature | TCP | UDP |
|---|---|---|
| Connection | Connection-oriented (3-way handshake) | Connectionless |
| Reliability | Guaranteed delivery, retransmission | Best effort, no guarantee |
| Ordering | In-order delivery | No ordering |
| Speed | Slower (overhead) | Faster (minimal overhead) |
| Flow Control | Yes (windowing) | No |
| Use Cases | HTTP, FTP, SSH, Email | DNS, DHCP, VoIP, Streaming |
TCP Three-Way Handshake
Client Server
| |
|-------- SYN -------------->|
| (seq=x) |
| |
|<------- SYN-ACK -----------|
| (seq=y, ack=x+1) |
| |
|-------- ACK -------------->|
| (ack=y+1) |
| |
| Connection Established |
|<----------------------------->|
Common Port Numbers
| Port | Protocol | Service |
|---|---|---|
| 20, 21 | TCP | FTP (data, control) |
| 22 | TCP | SSH |
| 23 | TCP | Telnet |
| 25 | TCP | SMTP |
| 53 | TCP/UDP | DNS |
| 67, 68 | UDP | DHCP |
| 80 | TCP | HTTP |
| 443 | TCP | HTTPS |
Port Visualizer Tasks- Explain the purpose of each step in the 3-way handshake
- List 5 TCP and 5 UDP services with their port numbers
- Explain why VoIP uses UDP instead of TCP
- Describe TCP flow control using windowing
4
Network Devices
20 minutes
Objective: Identify network devices and understand their roles at different OSI layers.
Device Roles
Hub (Layer 1)
Broadcasts all traffic to all ports. Creates one large collision domain. Obsolete in modern networks.
Switch (Layer 2)
Uses MAC addresses to forward frames. Creates separate collision domains per port. Maintains MAC address table (CAM).
Router (Layer 3)
Uses IP addresses to route packets between networks. Creates separate broadcast domains. Makes routing decisions using routing tables.
Multilayer Switch (Layer 2/3)
Combines switching and routing. Can perform inter-VLAN routing. Wire-speed Layer 3 forwarding.
Firewall (Layer 3-7)
Filters traffic based on rules. Stateful inspection tracks connection state. Next-gen firewalls inspect application layer.
Collision vs Broadcast Domains
| Device | Breaks Collision Domain? | Breaks Broadcast Domain? |
|---|---|---|
| Hub | No | No |
| Switch | Yes (per port) | No |
| Router | Yes | Yes |
| VLAN | Yes | Yes |
Devices Visualizer Tasks- Explain the difference between a hub and a switch
- Describe what information a switch uses to forward frames
- Explain why routers break broadcast domains
- Identify which device operates at Layer 3
5
VLANs & Layer 2 Switching
25 minutes
Objective: Understand VLANs, trunking, and Spanning Tree Protocol (STP).
VLANs (Virtual LANs)
Without VLANs: With VLANs:
+-------------------+ +-------------------+
| Switch | | Switch |
| +-------------+ | | +------+------+ |
| | One Large | | | |VLAN10|VLAN20| |
| | Broadcast | | -> | | HR | IT | |
| | Domain | | | | | | |
| +-------------+ | | +------+------+ |
+-------------------+ +-------------------+
All devices can Isolated broadcast
see each other domains per VLAN
VLAN Benefits: Security (isolation), Performance (smaller broadcast domains), Flexibility (logical grouping regardless of physical location).
Trunk Links
Access Port
Belongs to one VLAN only. Untagged traffic. Connects to end devices (PCs, printers).
Trunk Port
Carries multiple VLANs. Uses 802.1Q tagging. Connects switches together. Has native VLAN (untagged).
Spanning Tree Protocol (STP)
Problem: Switching Loops Solution: STP
+----------+ +----------+
| SW1 |<--------+ | SW1 |<--------+
| | | | (Root) | |
+----+-----+ | +----+-----+ |
| | DP | RP |
v | v |
+----+-----+ | +----+-----+ |
| SW2 |---------+ | SW2 |---------+
| | Loop! | | Blocked
+----------+ +----------+
Broadcasts multiply One path blocked
indefinitely (storm) to prevent loops
STP Port States
Blocking -> Listening -> Learning -> Forwarding
Tasks- Explain why VLANs improve network security
- Describe the difference between access and trunk ports
- Explain how STP prevents switching loops
- List the 4 STP port states in order
6
Routing Fundamentals
25 minutes
Objective: Understand routing concepts, static vs dynamic routing, and common routing protocols.
Routing Types
| Type | Static Routing | Dynamic Routing |
|---|---|---|
| Configuration | Manually defined | Auto-discovered |
| Scalability | Poor (many routes) | Good (self-managing) |
| Adaptability | None (manual updates) | Automatic failover |
| Resource Usage | Low | Higher (CPU, bandwidth) |
| Use Case | Small networks, stub routes | Large, complex networks |
Routing Protocols
RIP (Routing Information Protocol)
Distance-vector. Hop count metric (max 15). Simple but slow convergence. Legacy protocol.
OSPF (Open Shortest Path First)
Link-state. Cost metric (bandwidth-based). Fast convergence. Uses areas for scalability. Open standard.
EIGRP (Enhanced Interior Gateway Routing Protocol)
Hybrid (advanced distance-vector). Composite metric. Very fast convergence. Cisco proprietary (now open).
BGP (Border Gateway Protocol)
Path-vector. AS path metric. Internet backbone routing. Connects autonomous systems.
Administrative Distance
| Route Source | AD |
|---|---|
| Directly Connected | 0 |
| Static Route | 1 |
| EIGRP | 90 |
| OSPF | 110 |
| RIP | 120 |
| BGP (external) | 20 |
Lower AD = More Trusted: When multiple routes exist to the same destination, the router uses the route with the lowest administrative distance.
Reflection Questions
- When would you use static routing over dynamic routing?
- How does a router decide which route to use when there are multiple paths?
- What happens when a link fails in a network using OSPF?
- Why is it important to understand the OSI model for troubleshooting?
Tasks- Compare static and dynamic routing advantages
- Explain the difference between OSPF and EIGRP
- List 3 routing protocols with their administrative distances
- Explain why BGP is used for internet routing