Overview of Common Network Devices

Think of Internet as a big city’s postal system. Data stored on a server reaches to us through many checkpoints to our laptops or phones. Between ss and Internet there are several network devices that work together and has different responsibilities.

On high level

What is a Modem and how it connects your network to the internet?

Responsibility: Connect our local network To Internet service provider (ISP)

The modem converts signal so the data can move back and forth between our ISP which has fiber, DSL, cable signals and our home network which has Ethernet.

Without modem, we cannot connect to the Internet.

What Is a Router?

Responsibility: Direct traffic between devices and Internet.

When data comes

• Router decides which device it should go

• Also keeps track of which device asks for what

Router vs Modem

Switch vs Hub

1. HUB

   Responsibility: Broadcast everything to everyone.

   • Sends data to all devices

   • No thinking involved

   • Wastes bandwith

   • Rarely used

2. Switch

   Responsibility: Send data to intended device only.

   • Send data to specific devices

   • Learns MAC addresses

   • Fast and secure

   • Backbone of modern LANs

What is firewall?

Responsibility: Decides what to allow and what to block

Analogy: A security gate with some rules.

Important for:

• Controls incoming & outgoing traffic

• Protects DB, APIs and internal services

• Often implemented at:

  • Hardware

  • Cloud firewall

  • OS-level firewall

In production grade software, Security starts at firewall not with app.

What is load Balancer?

Responsibility: Distribute traffic across multiple servers.

Analogy: A toll booth with multiple lanes.

What is it’s need

• Horizontal Scaling

• High availability

• Zero downtown Deployments

How all these devices work together in a real-world setup?

Flow

1. Modem connects to ISP

2. Router directs traffic and manages devices

3. Firewall filters allowed traffic

4. Switch connects local machines

5. Load Balancer distributes requests to backend servers

Why This Matters for Software Engineers

• APIs sit behind firewalls

• Requests flow through load balancers

• Latency issues often involve routing or switching

• Security misconfigurations are network problems first

Understanding network devices help us:

• Debug production issues faster

• Design scalable architectures

• Communicate better with DevOps and SRE teams

Closing Statements

Network devices are not just cables and boxes, they are decision makers. Every device has different responsibilities and together they form the foundation of backend systems.