IPv6 does not use the same address class system found in IPv4, known as class-based addressing (classes A, B, C, D, and E).

This scheme was replaced in IPv4 by CIDR (Classless Inter-Domain Routing) addressing in the 90s to improve address allocation efficiency and is completely absent in IPv6 since its design.

Addressing in IPv6:

1. Address Structure: IPv6 uses 128-bit addresses, allowing for a much larger address space than IPv4. This massive address space allows considerable flexibility in assigning and managing addresses without the need for a class system.

2. Types of IPv6 Addresses: Instead of classes, IPv6 has several address types defined for different purposes, each with its own prefix indicating its function. Some of the most common types include:

• Unicast Addresses: They are used for one-to-one communication. They include:
  • Global Unicast: Similar to public addresses in IPv4, they are globally unique and are used for communication on the Internet.
  • Link-Local: Unique addresses only in the context of a single network segment. They are used for communication on the local network without the need for a global prefix.
  • Unique Local: Similar to private addresses in IPv4 (such as class A, B, C addresses in terms of internal use), these addresses are for use on local networks and are not routable on the Internet.
• Multicast Addresses: They replace IPv4 broadcast addresses and are used to transmit information to multiple receivers.
• Anycast Addresses: They are assigned to more than one interface but on different nodes, allowing packets to be sent to the closest address that shares that anycast address.

3. Subnetting in IPv6: Address allocation in IPv6 typically uses a prefix length of /64 for most subnets, although it is flexible and can vary depending on organizational or technical needs. This flexibility eliminates the need for fixed address classes and allows for more efficient use of address space.

Conclusion:

IPv6 was designed to be more flexible and efficient than IPv4, eliminating the need for the class system by using a more adaptable and expansive approach to address management.

This facilitates better network planning and utilization, as well as greater long-term scalability.