IP addresses are the unique identifiers that devices use to communicate on a network. In IPv4, these addresses are grouped into five classes: A, B, C, D, and E. Each class serves a specific purpose, and understanding them can help you make sense of network structures. Let’s break it down simply.
1. Class A: For Large Networks
- Range: 1 to 126 (e.g., 10.x.x.x)
- Purpose: Designed for big organizations like multinational companies.
- Structure:
- Network Bits: 8 (used to identify the network).
- Host Bits: 24 (used for devices in the network).
- Default Subnet Mask: 255.0.0.0
- Example: One network can have up to 16 million devices!
2. Class B: For Medium-Sized Networks
- Range: 128 to 191 (e.g., 172.16.x.x)
- Purpose: Perfect for universities, government offices, and medium-sized businesses.
- Structure:
- Network Bits: 16 (2 fixed + 14 usable).
- Host Bits: 16.
- Default Subnet Mask: 255.255.0.0
- Example: Each network can support 65,534 devices.
3. Class C: For Small Networks
- Range: 192 to 223 (e.g., 192.168.x.x)
- Purpose: Ideal for small businesses and home networks.
- Structure:
- Network Bits: 24.
- Host Bits: 8.
- Default Subnet Mask: 255.255.255.0
- Example: Each network supports up to 254 devices, making it great for small setups.
4. Class D: For Multicasting
- Range: 224 to 239
- Purpose: Used to send data to multiple devices at once (e.g., video streaming).
- Structure: No division into network and host bits.
- Default Subnet Mask: Not applicable.
- Example: Perfect for sending the same content to a group, like in live broadcasts.
5. Class E: For Experimental Use
- Range: 240 to 255
- Purpose: Reserved for research and testing.
- Structure: No division into network and host bits.
- Default Subnet Mask: Not applicable.
- Example: Not used in public networks.
Special IP Ranges
- Private IP Addresses:
- Reserved for internal use (not accessible on the internet).
- Examples:
- Class A: 10.0.0.0 – 10.255.255.255
- Class B: 172.16.0.0 – 172.31.255.255
- Class C: 192.168.0.0 – 192.168.255.255
- Loopback Address:
- 127.0.0.1: Used for testing your own device’s network setup.
- Broadcast Address:
- 255.255.255.255: Sends messages to all devices on a local network.
Quick Comparison Table
| Class | Range | Network Bits | Host Bits | Purpose |
|---|---|---|---|---|
| A | 1 – 126 | 8 | 24 | Large networks |
| B | 128 – 191 | 16 | 16 | Medium networks |
| C | 192 – 223 | 24 | 8 | Small networks |
| D | 224 – 239 | No division | No division | Multicasting |
| E | 240 – 255 | No division | No division | Experimental use |
