Nano Ink

IP Addressing

IP Addressing

An IP Address is a unique number assigned to every device in a network so it can be identified and communicate.

1. IP Address Basics

  • Example: 192.168.1.10 (IPv4)
  • Types:
    • Private IP — used inside local networks
    • Public IP — used on the internet
  • Versions:
    • IPv4 → 32-bit (like 192.168.1.1)
    • IPv6 → 128-bit (like fe80::1)

IPv4 Structure

2. Localhost (Loopback)

Used to refer to your own computer

  • 127.0.0.1 → Localhost
  • Range: 127.0.0.0 – 127.255.255.255
  • Used for:
    • Testing
    • Development
    • No internet needed

3. Private IP Addresses

Used inside homes, offices, LAN networks. Not accessible directly from internet.

Class A Private Range

Used in big networks

Range 10.0.0.0 – 10.255.255.255

Examples:

  • 10.0.0.1
  • 10.10.10.10
  • 10.1.1.1

Class B Private Range

Used in medium networks

Range 172.16.0.0 – 172.31.255.255

Examples:

  • 172.16.0.1
  • 172.20.5.10
  • 172.31.100.50

❗ Only 172.16 → 172.31 are private. Other 172.x are public.

Class C Private Range

Most common in home WiFi

Range 192.168.0.0 – 192.168.255.255

Examples:

  • 192.168.0.1
  • 192.168.1.1
  • 192.168.43.1 (Hotspot)

Private and Public IP

4. Public IP

Used on the internet. Assigned by ISP.

Examples:

  • 8.8.8.8 (Google DNS)
  • 142.250.183.14
  • 52.95.245.123

Anyone on internet can reach (unless blocked).

5. Special IP Ranges

APIPA (Automatic Private IP)

Assigned when no DHCP / WiFi problem

Range 169.254.x.x

Meaning:

  • Network problem
  • Failed to get IP

6. MAC Address

A MAC Address is a hardware identifier burned into the network card by the manufacturer.

Feature Description
Example A4:B3:22:1F:9C:10
Layer Data Link Layer
Size 48-bit address
Changes Never (normally)

Remember: MAC = Physical identity, IP = Logical identity

IP vs MAC

Feature IP Address MAC Address
Type Logical identifier Physical identifier
Layer Network Layer Data Link Layer
Assigned by Network/ISP Manufacturer
Changes Yes (dynamic) No (hardware)

7. Subnetting

Subnetting divides a large network into smaller networks.

Why Subnet?

  • Better performance
  • Improved security
  • Efficient IP usage

Example

Network: 192.168.1.0/24

Subnetted into:

  • 192.168.1.0/26
  • 192.168.1.64/26
  • 192.168.1.128/26
  • 192.168.1.192/26

8. CIDR Notation

CIDR = Classless Inter-Domain Routing

Represents network mask.

CIDR Subnet Mask Hosts
/24 255.255.255.0 254
/16 255.255.0.0 65,534
/32 255.255.255.255 1 (single IP)
/8 255.0.0.0 16,777,214

9. NAT (Network Address Translation)

NAT converts Private IP ↔ Public IP

Uses

  • Security
  • Limited IPv4 saving
  • Home routers

Types of NAT

Type Description
Static NAT One-to-one mapping
Dynamic NAT Pool of public IPs
PAT Port Address Translation (many-to-one)

NAT Diagram

10. Useful Commands

Show IP Addresses

ip addr

Show Neighbors (ARP Table)

ip neigh

Show Routing Table

ip route

Find Public IP

curl ifconfig.me

Force IPv4 or IPv6

curl -4 ifconfig.me
curl -6 ifconfig.me

Quick Reference

IP Type Range Use Case
Class A Private 10.0.0.0/8 Large networks
Class B Private 172.16.0.0/12 Medium networks
Class C Private 192.168.0.0/16 Home/Small networks
Loopback 127.0.0.0/8 Local testing
APIPA 169.254.0.0/16 No DHCP available