Internet & IP Addressing
What is the Internet?
The Internet is an interconnected network of billions of devices, with a collection of protocols that define a consistent communication format for devices to send and receive data to and from one another.
Think of it as a giant highway system where every car (data packet) follows the same traffic rules (protocols) regardless of where it came from or where it is going.
Key idea: No single company owns the internet. It is a cooperative system of networks run by ISPs, governments, universities, and private companies — all agreeing to use the same protocols.
IP Addressing
Every device on a network has an IP (Internet Protocol) address — a unique identifier that allows data to be routed to the right destination.
IPv4
The most common format. Written as four groups of numbers separated by dots:
192.168.1.10Each group is a number from 0 to 255 (8 bits), making the full address 32 bits long. This allows for ~4.3 billion unique addresses.
IPv6
Because IPv4 addresses are running out, IPv6 was introduced. It uses 128 bits and is written in hexadecimal:
2001:0db8:85a3:0000:0000:8a2e:0370:7334Public vs. Private IP Addresses
| Type | Range | Use |
|---|---|---|
| Private | 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16 | Internal networks (LAN) |
| Public | Everything else | Accessible on the internet |
IP Address = Network portion + Host portion
The network portion identifies which network the device is on. The host portion identifies the specific device within that network.
Subnetting & CIDR
CIDR — Classless Inter-Domain Routing
CIDR is a method for efficiently allocating IP addresses. Instead of rigid class-based blocks, CIDR uses a prefix length (subnet mask) to define how many bits are the network portion.
192.168.1.0/24The /24 means the first 24 bits are the network part. The remaining 8 bits are for hosts.
Network: 192.168.1 (24 bits)
Hosts: .0 → .255 (8 bits = 256 addresses, 254 usable)Common Subnet Sizes
| CIDR | Subnet Mask | Hosts (usable) | Common Use |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 | Large ISP networks |
| /16 | 255.255.0.0 | 65,534 | Large company network |
| /24 | 255.255.255.0 | 254 | Typical office/home network |
| /28 | 255.255.255.240 | 14 | Small server subnet |
| /30 | 255.255.255.252 | 2 | Point-to-point links |
| /32 | 255.255.255.255 | 1 | Single host (used in routes) |
Why DevOps Engineers Need Subnetting
In cloud environments (AWS, GCP, Azure), you design your own network. You need to:
- Create a VPC with a CIDR block (e.g.,
10.0.0.0/16) - Divide it into subnets (public:
10.0.1.0/24, private:10.0.2.0/24) - Ensure subnets don’t overlap