Public vs Private IP

Not every IP address is directly reachable from the internet.

There are two important categories:

• Private IP
• Public IP

Private IP

A private IP is used inside a local network.

Examples:

192.168.1.10
10.0.0.5
172.16.2.20

Your laptop, phone, smart TV, and printer usually have private IP addresses at home.

Private IPs are not directly reachable from the public internet.

Public IP

A public IP is reachable on the internet.

Your home router usually has one public IP given by your internet provider.

Public servers also have public IPs.

Example:

Browser → Public IP of a web server

If a backend API is deployed on the internet, users ultimately reach it through a public IP address, directly or through a load balancer, CDN, or reverse proxy.

Why do we use Private IPs?

There are not enough IPv4 addresses for every device in the world to have a unique public IPv4 address.

So local networks reuse private IP ranges.

Example:

Your laptop can be:

192.168.1.10

My laptop can also be:

192.168.1.10

That is okay because they are inside different private networks.

Common Private IP Ranges

Interview Answer

If an interviewer asks:

What is the difference between public and private IP?

You can answer:

A private IP is used inside a local network and is not directly reachable from the internet. A public IP is globally reachable on the internet. Private IP ranges can be reused across different local networks, while public IPs must be globally unique.