IP Address Classes

IP address classes were a part of the original addressing scheme defined in the Internet Protocol (IPv4). However, the concept of classes is largely obsolete due to the adoption of Classless Inter-Domain Routing (CIDR), which allows for more flexible allocation of IP addresses. Nonetheless, understanding the historical IP classes can provide some context.

There were originally three main IP classes: Class A, Class B, and Class C. Each class had a different range of possible IP addresses and was intended for different types of networks.

  1. Class A:
    • Range: 1.0.0.0 to 126.0.0.0
    • Example: 10.0.0.0 (with subnet mask 255.0.0.0)
    • Designed for large networks with a vast number of hosts.
  2. Class B:
    • Range: 128.0.0.0 to 191.255.0.0
    • Example: 172.16.0.0 (with subnet mask 255.255.0.0)
    • Suitable for medium-sized networks.
  3. Class C:
    • Range: 192.0.0.0 to 223.255.255.0
    • Example: 192.168.0.0 (with subnet mask 255.255.255.0)
    • Intended for smaller networks.
  4. Class D (Multicast):
    • Range: 224.0.0.0 to 239.255.255.255
    • Reserved for multicast groups.
  5. Class E (Experimental):
    • Range: 240.0.0.0 to 255.255.255.255
    • Reserved for experimental purposes.

CIDR (Classless Inter-Domain Routing) has largely replaced the traditional class system. With CIDR, any number of contiguous IP addresses can be grouped together, allowing for more efficient use of address space and flexibility in allocating addresses.