Role of IP Addresses in System Design and Architecture
But in reality, IP addresses are one of the simplest and most important ideas behind how systems work.
If you understand IP addresses properly, many things suddenly become clear:
How websites work
Why databases are not exposed to the internet
How systems scale safely
Let’s break this down slowly and simply.
What Is an IP Address?
An IP address is a number that identifies a device on a network.
Every device connected to a network needs one:
Mobile phone
Laptop
Server
Database
Think of an IP address like a home address.
If someone wants to send you a letter, they need your home address
If one computer wants to send data to another, it needs the IP address
Example:
192.168.1.10
This number tells the network:
“Send data to this exact device.”
Without IP addresses, computers would not know where to send data.
Why Are IP Addresses Important?
IP addresses make three things possible:
Identification – knowing which device is which
Communication – sending and receiving data
Routing – finding the correct path through the network
Every time you:
Open a website
Watch a YouTube video
Call an API
IP addresses are working silently in the background.
IPv4 and IPv6: Why Do We Have Two Types?
IPv4 (The Old One)
IPv4 is the older and most common type of IP address.
It looks like this:
192.168.0.1
IPv4 has a limited number of addresses—about 4 billion.
Years ago, this felt like more than enough.
But today:
Billions of phones
Cloud servers
Smart TVs
IoT devices
We ran out of IPv4 addresses.
IPv6 (The New One)
IPv6 was created to solve this problem.
It looks longer:
2001:db8::1
IPv6 has an almost unlimited number of addresses.
Important note:
As a developer, you usually don’t need to manage IPv6 manually, but you should know why it exists.
How Does IPv6 Have “Almost Unlimited” Addresses?
At first glance, IPv6 addresses look confusing and unnecessarily long.
But the reason behind this length is very simple.
The secret lies in how many bits are used to create the address.
IPv4 vs IPv6: The Core Difference (Bits)
IPv4 Uses 32 Bits
IPv4 addresses are made using 32 bits (binary digits).
That means:
2 × 2 × 2 × ... (32 times) = 2³²
Which equals:
4,294,967,296 addresses
Roughly 4.3 billion
This sounded huge in the 1980s.
Today, it is not enough.
IPv6 Uses 128 Bits
IPv6 addresses are made using 128 bits.
That means:
2¹²⁸ addresses
Which equals approximately:
340 undecillion addresses
Written as:
340,000,000,000,000,000,000,000,000,000,000,000
This number is so large that it is hard to imagine.
A Simple Analogy (Very Important)
IPv4 Is Like Phone Numbers
Limited digits
We eventually ran out
Needed sharing and workarounds (like NAT)
IPv6 Is Like Giving Every Grain of Sand an Address
A popular analogy:
With IPv6, we can assign billions of IP addresses to every human on Earth
and still not run out.
In fact:
Every phone
Every laptop
Every server
Every IoT device
Every virtual machine
Can have its own unique public IP.
Why IPv6 Doesn’t “Feel” Unlimited, But Practically Is
Technically:
IPv6 is finite
But practically:
We will never exhaust it
Even with future technologies
To put it in perspective:
IPv4 shortage happened within decades
IPv6 will last for thousands of years, even with massive growth
Why Does IPv6 Need So Many Addresses?
Because modern systems are very different:
Cloud servers scale up and down
Containers come and go
IoT devices are everywhere
Smart homes, cars, watches, sensors
IPv6 was designed for:
Massive scale
Future-proof growth
Simpler networking (less need for NAT)
Then Why Do We Still Use Private IPs?
Important clarification:
Even though IPv6 has plenty of addresses:
Private networks are still useful
Security and isolation still matter
Internal systems should not be exposed directly
So IPv6 solves the shortage problem,
but does not replace good system design principles.
One-Line Summary
IPv6 has almost unlimited addresses because it uses 128 bits instead of 32 bits, increasing the address count from billions to numbers so large they are practically impossible to exhaust.
Public IP vs Private IP (The Most Important Concept)
This is the key idea in system design.
What Is a Public IP?
A public IP address is visible on the internet.
If a system has a public IP:
Anyone on the internet can reach it
It must be secured carefully
Examples:
Websites
Public APIs
Load balancers
Think of a public IP as a main gate of a building.
What Is a Private IP?
A private IP address works only inside a private network.
Examples:
192.168.x.x
10.x.x.x
Private IPs:
Are not visible on the internet
Are used inside homes, offices, and cloud networks
Think of private IPs as room numbers inside a building.
Why Do We Need Private IPs?
1. Safety and Security
Private IPs keep important systems hidden.
Databases, internal services, and backend systems:
Should NOT be reachable from the internet
Should only talk to trusted systems
Private IPs make this possible.
2. Saves Internet IP Addresses
Instead of giving every server a public IP:
Many servers use private IPs
One public IP acts as a gateway
This helped the internet survive IPv4 shortages.
3. Better System Design
Good systems:
Expose only what is necessary
Keep everything else private
Private IPs encourage clean and safe architecture.
How IP Addresses Fit Into System Design
Let’s look at a very common real-world design.
Simple Web Application Architecture
User
↓
Public IP (Load Balancer)
↓
Private IP (Backend Servers)
↓
Private IP (Database)
Only the load balancer has a public IP.
Everything behind it:
Uses private IPs
Is hidden from the internet
This is how almost all modern systems work.
Load Balancing Made Simple
A load balancer:
Has one public IP
Sends traffic to many backend servers
Why this is powerful:
Servers can be added or removed anytime
Users always talk to the same IP
System scales easily
Users never know how many servers exist behind the scenes.
What About Microservices?
Modern systems have many small services:
Auth service
Payment service
Notification service
These services:
Use private IPs
Talk to each other internally
Usually use names instead of IP numbers
This allows:
Easy scaling
Easy replacement
Fewer failures
IP Addresses Can Change (And That’s Normal)
In cloud systems:
Servers are created and destroyed
IPs change frequently
Good systems:
Do not depend on fixed IPs
Use load balancers or names
Keep working even when IPs change
Bad systems:
Break when an IP changes
Common Interview Questions (Simple Answers)
Why not give every server a public IP?
Because it is:
Unsafe
Expensive
Unnecessary
How do private servers access the internet?
They use something called NAT, which acts like a shared exit door to the internet.
What happens if a server’s IP changes?
Good design → nothing happens
Bad design → system crashes
Does IPv6 remove the need for private networks?
No.
Private networks are used for:
Security
Control
Clean architecture
Not just for IP shortages.
Final Takeaway (Remember This)
You don’t need to memorize IP formats.
Just remember this simple rule:
Public IPs are for entry points.
Private IPs are for internal systems.
If you follow this rule, your system will be:
Safer
Easier to scale
Easier to maintain
Easier to explain in interviews
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