1.7 Given a scenario, use appropriate IPv4 network addressing
IPv4 Address Classes
📘CompTIA Network+ (N10-009)
IPv4 Address Classes
IPv4 addresses are 32-bit numbers used to identify devices on a network. To make them easier to manage, IPv4 addresses are divided into classes. Each class has a specific range, purpose, and number of available hosts. Knowing this is essential for network planning and the CompTIA exam.
1️⃣ Class A
Purpose: Designed for very large networks, such as large organizations or ISPs.
Address Range: 1.0.0.0 to 126.255.255.255
- The first octet (the first 8 bits) identifies the network.
- The remaining three octets identify hosts within that network.
Default Subnet Mask: 255.0.0.0 (or /8 in CIDR notation)
Key Points:
- Only the first 8 bits are for the network ID; the remaining 24 bits are for host IDs.
- Supports over 16 million hosts per network.
- Often used by very large organizations or major ISPs.
Example in IT environment: A multinational company could assign Class A addresses to its global network to manage millions of devices without subnetting heavily.
2️⃣ Class B
Purpose: Designed for medium to large networks, such as universities or large businesses.
Address Range: 128.0.0.0 to 191.255.255.255
- The first two octets identify the network.
- The last two octets identify hosts.
Default Subnet Mask: 255.255.0.0 (or /16 in CIDR notation)
Key Points:
- Supports 65,534 hosts per network.
- More networks are available than Class A, but fewer hosts per network.
Example in IT environment: A university could use Class B addresses to assign IPs to different departments while still accommodating thousands of students and devices.
3️⃣ Class C
Purpose: Designed for small networks, like small offices or branch offices.
Address Range: 192.0.0.0 to 223.255.255.255
- The first three octets identify the network.
- The last octet identifies hosts.
Default Subnet Mask: 255.255.255.0 (or /24 in CIDR notation)
Key Points:
- Supports 254 hosts per network.
- Most commonly used class for small networks today.
- Very practical for assigning IPs to devices like servers, printers, and workstations.
Example in IT environment: A small office with 200 devices can use a Class C network to assign each device a unique IP address without wasting IPs.
4️⃣ Class D
Purpose: Used for multicast groups rather than standard network hosts.
Address Range: 224.0.0.0 to 239.255.255.255
Key Points:
- Not assigned to regular devices.
- Used to send a single data stream to multiple devices simultaneously (multicasting).
- Example: Video conferencing or streaming software in an enterprise environment may use Class D addresses to efficiently send data to many devices at once.
5️⃣ Class E
Purpose: Reserved for experimental or future use.
Address Range: 240.0.0.0 to 255.255.255.254
Key Points:
- Not used in standard networks.
- Can be used for research or future IP features.
- Rarely encountered in practical IT environments.
Quick Reference Table for Exams
| Class | Range | Default Subnet Mask | Hosts per Network | Purpose |
|---|---|---|---|---|
| A | 1.0.0.0 – 126.255.255.255 | 255.0.0.0 (/8) | 16,777,214 | Very large networks |
| B | 128.0.0.0 – 191.255.255.255 | 255.255.0.0 (/16) | 65,534 | Medium/large networks |
| C | 192.0.0.0 – 223.255.255.255 | 255.255.255.0 (/24) | 254 | Small networks |
| D | 224.0.0.0 – 239.255.255.255 | N/A | N/A | Multicast |
| E | 240.0.0.0 – 255.255.255.254 | N/A | N/A | Experimental/future use |
✅ Exam Tips
- Remember the first octet ranges for Class A, B, and C. This is commonly tested.
- Know default subnet masks for A, B, and C.
- Understand that Class D is multicast and Class E is experimental.
- When given an IP, you should be able to identify its class instantly.
