Decoding the IP address classification system

• In IPv4, there are 4,294,967,296 IP addresses. These addresses are organised into five IP classes — A, B, C, D, and E.
• Class A addresses catered to largescale networks, class B served medium-sized networks, and class C was designated for small networks, whereas class D and class E were reserved for multicast groups and experimental purposes respectively.

In the labyrinthine world of the internet, every device connected to the global network requires a unique identifier – an IP address. Historically, these addresses were categorised into different classes, a system that was pivotal in the early days of the internet but has since evolved. Let‘s embark on a journey through the classification of IP addresses, exploring their origins, significance, and how they shaped the architecture of our digital communications.

Also read: What are IP addresses and why they are important?

The structure of IP addresses

An IP address is constituted by 32 bits, apportioned into quartet segments, demarcated by periods. Each segment encapsulates 8 bits, tantamount to 1 byte or octet. Leveraging 32 bits with dual potential values for each locus, the binary system engenders 4,294,967,296 (2^32) unique combinations, translating to a plethora of IP addresses. These addresses may operate sans an organisational scheme or within a scheme that systematises them, thereby facilitating easier access.

If addresses are used without any addressing scheme, all routers on the network will need to store the address of each and every interface on the network. The network’s magnitude could influence routing efficacy; a larger network might exacerbate routing complexities. For efficient routing, addresses are organised into the hierarchical addressing scheme. In this scheme, all addresses are categorised into five classes (A, B, C, D, and E) and each address is bifurcated into two components — the network address and the host address.

Also read: What is a public IP address?

Class A: The realm of large networks

Class A addresses were designated for large-scale networks, typically reserved for major corporations and governments. With a range starting from 1.0.0.1 to 126.255.255.254, class A addresses offered a vast pool of host addresses, allowing for extensive internal network configurations. Each class A network could support over 16 million hosts, making it ideal for organisations with substantial networking requirements.

Also read: How to secure an IP address?

Class B: The middle ground

Class B addresses catered to medium-sized networks, such as universities and regional service providers. Spanning from 128.0.0.1 to 191.255.255.254, these addresses struck a balance between network size and address availability. A class B network could accommodate up to 65,534 hosts, offering flexibility and scalability for organisations that did not require the colossal address space of Class A.

Class C: The small network solution

For small businesses and local networks, class C addresses were the go-to choice. Ranging from 192.0.0.1 to 223.255.255.254, these addresses supported a maximum of 254 hosts, making them perfect for smaller organisations or home networks. Their limited address space encouraged efficient use and conservation of IP addresses.

Class D and class E: Multicast and reserved spaces

Class D addresses, ranging from 224.0.0.0 to 239.255.255.255, were designated for multicast groups, enabling one-to-many communication without the need for individual addresses. This class facilitated efficient data transmission across multiple recipients simultaneously.

Class E addresses, from 240.0.0.0 to 255.255.255.255, were reserved for future use and experimentation. They are not currently assigned for public use, serving instead as a sandbox for potential innovations in networking protocols.