📚 What are IP Address Classes?

Think of it like different sizes of buildings:

IP addresses are divided into 5 classes (A, B, C, D, E) based on how they're used and how big the networks are.

Easy Analogy:

🏢 Class A = Huge skyscraper (millions of rooms)

🏬 Class B = Large office building (thousands of rooms)

🏠 Class C = Small apartment building (hundreds of rooms)

📡 Class D = Broadcasting station (sends to many at once)

🔬 Class E = Research lab (experimental use only)

🎯 How to Identify IP Classes

Super Simple Rule: Look at the FIRST number!

Class A 1 - 126

If first number is between 1 and 126

Example: 10.0.0.1 → Class A

Class B 128 - 191

If first number is between 128 and 191

Example: 172.16.0.1 → Class B

Class C 192 - 223

If first number is between 192 and 223

Example: 192.168.1.1 → Class C

Class D 224 - 239

If first number is between 224 and 239

Example: 224.0.0.1 → Class D

Class E 240 - 255

If first number is between 240 and 255

Example: 240.0.0.1 → Class E

🏠 Private vs Public IP Addresses

Two types of IP addresses:

🔒 Private IPs (Inside your home/office)

These addresses are used INSIDE networks and cannot be used on the internet.

Class A Private: 10.0.0.0 - 10.255.255.255

Class B Private: 172.16.0.0 - 172.31.255.255

Class C Private: 192.168.0.0 - 192.168.255.255

Example: Your home WiFi router probably uses 192.168.1.1

🌐 Public IPs (On the internet)

These addresses are used on the internet and are unique worldwide.

Example: Google's public IP is 8.8.8.8

🎓 Class Details Explained

Class A - For Huge Organizations

  • Range: 1.0.0.0 to 126.255.255.255
  • Default Mask: 255.0.0.0 (/8)
  • Network Bits: 8 bits
  • Host Bits: 24 bits
  • Hosts per Network: 16,777,214
  • Who uses it: Very large companies, ISPs

Class B - For Medium Organizations

  • Range: 128.0.0.0 to 191.255.255.255
  • Default Mask: 255.255.0.0 (/16)
  • Network Bits: 16 bits
  • Host Bits: 16 bits
  • Hosts per Network: 65,534
  • Who uses it: Universities, large businesses

Class C - For Small Networks

  • Range: 192.0.0.0 to 223.255.255.255
  • Default Mask: 255.255.255.0 (/24)
  • Network Bits: 24 bits
  • Host Bits: 8 bits
  • Hosts per Network: 254
  • Who uses it: Small businesses, homes

Class D - For Multicast

  • Range: 224.0.0.0 to 239.255.255.255
  • Purpose: Sending data to multiple destinations at once
  • No subnet mask: Not used for regular addressing
  • Who uses it: Video streaming, online gaming

Class E - For Research

  • Range: 240.0.0.0 to 255.255.255.255
  • Purpose: Reserved for experimental use
  • Not used: Cannot be assigned to devices
  • Who uses it: Research and development only

❓ Common Questions

Why is 127.x.x.x missing from Class A?

127.0.0.0 to 127.255.255.255 is reserved for "loopback" addresses (your computer talking to itself). The most famous is 127.0.0.1 (localhost).

Do we still use IP classes today?

Not really! Modern networks use CIDR (Classless Inter-Domain Routing) which is more flexible. But understanding classes helps you learn networking basics.

Can I use any IP address I want at home?

You should use private IP addresses (10.x.x.x, 172.16-31.x.x, or 192.168.x.x). These won't conflict with internet addresses.

What's the difference between IPv4 classes and IPv6?

IPv6 doesn't use classes at all! It has so many addresses (340 undecillion!) that it doesn't need this classification system.