An IP Address (Internet Protocol Address) is a unique address assigned to a device or network interface so that devices can identify and communicate with each other over a network.
1. Why Do We Need an IP Address?
When your application wants to communicate with another server, it needs to know where that server is.
Client | | Request ↓ IP Address | ↓ Server
For example:
google.com
↓ DNS
142.250.x.x
↓
Server
DNS finds the IP address. The IP address identifies the destination.
2. IPv4
IPv4 is the most commonly known IP addressing format.
192.168.1.10
IPv4 contains 32 bits and is represented using four numbers separated by dots.
192 . 168 . 1 . 10
Each section can contain a value from 0 to 255.
3. IPv6
IPv6 was introduced because the number of available IPv4 addresses is limited.
2001:0db8:85a3:0000:0000:8a2e:0370:7334
IPv6 uses 128 bits, providing a vastly larger address space than IPv4.
4. Public IP vs Private IP
Private IP
Used inside a private network such as your home, office, or cloud VPC.
192.168.1.10 10.0.0.5 172.16.0.10
Public IP
Used to identify a device or service on the public Internet.
Internet | ↓ Public IP | ↓ Router / Load Balancer / Server
5. Static IP vs Dynamic IP
| Static IP | Dynamic IP |
|---|---|
| Usually remains the same | Can change |
| Useful for servers | Common for client devices |
| More predictable | Usually assigned using DHCP |
6. IP Address and Port
An IP address identifies the machine/network interface. A port identifies the application or service on that machine.
192.168.1.10:443
│ │
│ └── Port
│
└────────── IP Address
For example:
192.168.1.10:80 → HTTP 192.168.1.10:443 → HTTPS 192.168.1.10:5000 → Application/API
7. IP Address in a Real System
User ↓ DNS ↓ Public IP ↓ Load Balancer ↓ Private IP ↓ Application Server ↓ Database
In a cloud architecture, users typically connect through a public endpoint, while internal services communicate using private IP addresses.
8. Interview Questions
What is an IP address?
An IP address is a logical network address used to identify a device or network interface and enable communication between systems.
What is the difference between IPv4 and IPv6?
IPv4 uses 32-bit addresses, while IPv6 uses 128-bit addresses and provides a much larger address space.
What is the difference between public and private IP?
A public IP is reachable over the Internet, while a private IP is used inside a private network and is not directly reachable from the public Internet.
Does an IP address identify an application?
No. The IP identifies the network destination. The port identifies the service/application listening on that destination.
Key Takeaway
IP Address = Where is the machine?
Port = Which application?
DNS = What IP belongs to this domain?