Lesson 05 — Routing & Switching

Lesson Overview

Imagine working in a large office building with hundreds of employees.

Some employees work on the same floor, while others are located in different buildings around the world.

Messages sent within the same floor are delivered quickly, but messages destined for another building require a delivery service that knows the correct route.

Computer networks work in exactly the same way.

Switches communicate within the same network.
Routers connect different networks together.

Together, routing and switching form the backbone of every modern network, from home Wi-Fi to global cloud providers such as AWS, Microsoft Azure, and Google Cloud.

Understanding these concepts is essential for Cloud Engineers, Network Engineers, Cybersecurity Professionals, DevOps Engineers, and Solutions Architects.

Learning Objectives

After completing this lesson, you will be able to:

Explain the purpose of switches and routers.
Understand Layer 2 and Layer 3 communication.
Differentiate between switching and routing.
Understand MAC addresses and IP addresses.
Learn how routing decisions are made.
Explore enterprise and cloud networking concepts.

What is Switching?

Switching is the process of forwarding data between devices on the same Local Area Network (LAN).

A switch receives a frame and forwards it only to the correct destination device.

Example:

Laptop

↓

Switch

↓

Printer

The communication remains inside the same network.

What is Routing?

Routing is the process of forwarding data between different networks.

A router determines the best path for data to travel from one network to another.

Example:

Laptop

↓

Office Router

↓

Internet

↓

AWS Cloud

↓

EC2 Server

Without routing, devices outside your local network could never communicate.

Switching vs Routing

Switching	Routing
Operates within the same network	Connects different networks
Uses MAC Addresses	Uses IP Addresses
Layer 2 Device	Layer 3 Device
Faster local communication	Determines best network path
Performed by Switches	Performed by Routers

Both technologies work together to provide seamless communication.

Understanding MAC Addresses

Every network interface has a unique physical address called a MAC (Media Access Control) Address.

Example:

00:1A:2B:3C:4D:5E

Characteristics:

Assigned by the manufacturer.
Unique to the device.
Used within the local network.
Operates at Layer 2 of the OSI Model.

Switches use MAC addresses to forward frames.

Understanding IP Addresses

An IP address identifies a device across networks.

Example:

192.168.1.25

Characteristics:

Logical address.
Assigned manually or via DHCP.
Used for communication between networks.
Operates at Layer 3.

Routers use IP addresses to determine where data should go.

How a Switch Works

Imagine four computers connected to a switch.

Computer A

        │

Computer B ── Switch ── Computer C

        │

Computer D

When Computer A sends data to Computer C:

The switch checks the destination MAC address.
It looks in its MAC Address Table.
It forwards the frame only to Computer C.

This makes local communication fast and efficient.

MAC Address Table

Every switch maintains a table of connected devices.

Example:

MAC Address	Port
AA:AA:AA:AA	Port 1
BB:BB:BB:BB	Port 2
CC:CC:CC:CC	Port 3
DD:DD:DD:DD	Port 4

The switch learns these addresses automatically.

This process is called MAC Learning.

How a Router Works

Imagine your laptop wants to access a website hosted in AWS.

Laptop

↓

Home Router

↓

ISP

↓

Internet

↓

AWS Router

↓

EC2 Instance

The router examines the destination IP address and decides the best route to reach the destination.

Routing Table

Routers maintain a Routing Table that contains known network paths.

Example:

Destination Network	Next Hop
192.168.1.0/24	Local
10.0.0.0/16	Router A
Default Route	Internet Gateway

The router selects the best matching route before forwarding traffic.

Default Gateway

A Default Gateway is the router that devices use when communicating outside their local network.

Example:

Laptop

IP Address

192.168.1.50

↓

Default Gateway

192.168.1.1

↓

Internet

Every device on a network typically has one default gateway configured.

Broadcast Domain

A broadcast domain is a group of devices that receive broadcast traffic.

Switches forward broadcast traffic to all devices within the same VLAN.

Routers separate broadcast domains, reducing unnecessary network traffic.

This improves performance and scalability.

Collision Domain

A collision domain is an area where data transmissions could interfere with one another.

Modern switches create a separate collision domain for each port, greatly improving network efficiency.

Layer 2 vs Layer 3 Communication

Same Network

Laptop

↓

Switch

↓

Server

=========================

Different Networks

Laptop

↓

Switch

↓

Router

↓

Internet

↓

Cloud Server

Remember:

Switches handle local communication.
Routers connect different networks.

Static Routing

In static routing, administrators manually configure routes.

Advantages:

Simple
Predictable
Easy to understand

Disadvantages:

Doesn’t scale well.
Requires manual updates.

Used in:

Small networks
Labs
Simple enterprise environments

Dynamic Routing

Large organizations use dynamic routing protocols.

These protocols automatically learn network paths.

Examples:

OSPF
BGP
EIGRP
RIP

Advantages:

Automatic updates
Better scalability
Faster recovery
Improved redundancy

Cloud providers rely heavily on dynamic routing.

Routing in Cloud Computing

Cloud platforms provide virtual routing services.

Examples:

AWS

VPC Route Tables
Internet Gateway
NAT Gateway
Transit Gateway

Azure

Route Tables
Virtual Network Gateway

Google Cloud

Cloud Router
VPC Routes

Although these are virtual devices, they perform the same routing functions as physical routers.

Switching in Cloud Computing

Traditional physical switches are replaced by software-defined networking (SDN).

Examples:

AWS Elastic Network Interface (ENI)
Azure Virtual Network
Google Cloud VPC

Cloud networking abstracts the physical infrastructure while maintaining the same networking principles.

Routing in Cybersecurity

Security teams rely on routing to:

Segment networks.
Protect sensitive systems.
Configure firewalls.
Build secure VPNs.
Investigate network paths.
Control traffic flow.

Proper routing improves both security and performance.

Real-World Example

Imagine an employee opens:

https://portal.company.com

The request travels like this:

Employee Laptop

↓

Office Switch

↓

Office Router

↓

ISP

↓

Internet

↓

Cloud Load Balancer

↓

Application Server

↓

Database

↓

Response Returned

Throughout this process:

Switches handle communication inside the office.
Routers move traffic between networks.
Cloud routers direct traffic inside the cloud environment.

Common Commands

Windows

route print

tracert google.com

Linux

ip route

traceroute google.com

Cisco IOS

show ip route

show mac address-table

You’ll use these commands in future networking and cloud labs.

Best Practices

As an IT professional:

Design networks with scalability in mind.
Separate networks using routers and VLANs.
Keep routing tables organized.
Document network topology.
Monitor routing changes.
Secure routing infrastructure.
Use dynamic routing where appropriate.
Regularly review network performance.

Key Takeaways

After completing this lesson, you should understand:

The difference between routing and switching.
The purpose of routers and switches.
MAC addresses vs IP addresses.
Routing tables and default gateways.
Static and dynamic routing.
How routing supports cloud and enterprise networking.

Summary

Routing and switching are two of the most fundamental concepts in networking.

Switches efficiently connect devices within a local network, while routers enable communication across different networks and the Internet.

Whether you’re building cloud infrastructure, configuring enterprise networks, deploying Kubernetes clusters, or securing cloud environments, routing and switching knowledge will be used every day throughout your IT career.

Next Lesson

➡️ Lesson 06 — Domain Name System (DNS)

In the next lesson, you’ll learn how DNS translates human-friendly domain names into IP addresses, discover how Internet name resolution works, and understand why DNS is one of the most critical services in modern networking and cloud computing.