Understanding IPv4 Address Classes and Their Uses

IPv4 classes are a historical way to describe the shape of a network. They still appear in search results, documentation and conversations about Class C addresses, but modern networks use CIDR to choose the size and specificity they actually need.

Why IPv4 classes still appear

IPv4 addresses contain 32 bits and are usually written as four decimal octets, such as 192.168.1.1. The original classful model grouped those addresses into fixed ranges. It helped early networks organize quickly, but it could not match the precise capacity and routing choices operators need today.

For an ISP, hosting provider or cloud team, class terminology is useful as a reference point. The commercial question is practical: what block can you route, assign and grow with while keeping services reachable?

The five IPv4 classes

Historical IPv4 classes and their practical meaning

Class	Historical range	Historical use
A	1.0.0.0–126.255.255.255	Very large networks; 127.0.0.0/8 is reserved for loopback
B	128.0.0.0–191.255.255.255	Medium-sized network designs
C	192.0.0.0–223.255.255.255	Smaller network designs and the familiar /24 shape
D	224.0.0.0–239.255.255.255	Multicast groups
E	240.0.0.0–255.255.255.255	Experimental or reserved space

The table explains the vocabulary; it is not a modern allocation plan. Today, CIDR lets you select prefixes without being trapped inside a fixed class boundary.

Historical masks and host capacity

Class	Default mask / prefix	Network / host bits	Hosts per conventional subnet
A	255.0.0.0 /8	8 / 24	16,777,214
B	255.255.0.0 /16	16 / 16	65,534
C	255.255.255.0 /24	24 / 8	254

These historical host counts use 2 to the power of the host bits, minus the network and broadcast addresses. Class D multicast and Class E reserved space do not use this unicast network/host split. Modern CIDR subnet designs use their selected prefix.

Special address ranges

• Loopback: 127.0.0.0/8 is used by a device to talk to itself for testing and local functions.
• Private IPv4: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 are designed for internal networks and are not publicly routed.
• APIPA: 169.254.0.0/16 can be self-assigned when a device cannot reach DHCP.
• Multicast: Class D space supports delivery to a group of receivers rather than one destination.

From classes to CIDR planning

With CIDR, /24 describes 256 total IPv4 addresses, while /23 doubles that space and /22 doubles it again. The right prefix depends on your route policy, customer assignments, infrastructure and growth plan.

This is where the historical lesson becomes useful: classful language explains the past, but flexible prefixes power the network you operate now. Learn more in Understanding IP Address Blocks.

The IANA IPv4 registry documents address-space assignments. Read how IP addresses work and how allocation works to connect the class chart with real operations. When planning both protocols, consider IPv4 and IPv6 adoption through the customers and applications you need to reach.

Plan the capacity your network needs

LARUS connects network operators to Unlimited IPv4 and IPv4 Continuity, giving your customer growth a clearer path to stable public capacity. Explore LARUS Continuity when your next network decision needs to support more than a single deployment.