What is CIDR?

Classless Inter-Domain Routing (CIDR) is a method of allocating IP addresses and routing internet traffic using variable-length network prefixes instead of fixed address classes. Introduced in 1993, Classless Inter-Domain Routing replaced the inefficient class-based addressing system, helping conserve IPv4 address space while making routing more scalable. This notation combines an IP address with a prefix length, such as 192.168.1.0/24, where /24 indicates that the first 24 bits identify the network.

How does CIDR notation work?

This notation consists of an IP address followed by a forward slash and a number representing the network prefix length. The prefix determines how many bits belong to the network portion, while the remaining bits are available for host addresses.

Smaller prefix numbers create larger networks, while larger prefix numbers create smaller, more specific subnets. This flexibility allows organizations to allocate only the number of IP addresses they actually need.

Why is it important?

Before CIDR, IP addresses were assigned using fixed Class A, B, and C networks, often wasting large address blocks. CIDR introduced variable-length subnetting, allowing organizations and internet service providers to allocate addresses more efficiently.

CIDR also enables route aggregation, where multiple networks are advertised as a single route. This significantly reduces the size of internet routing tables, improving router performance and network scalability.

Where is CIDR used?

CIDR is widely used across enterprise networks, cloud platforms, and internet service providers. Network administrators rely on CIDR for subnet planning, virtual private clouds (VPCs), firewall policies, VPN configurations, and access control lists (ACLs).

Cloud providers such as AWS, Microsoft Azure, and Google Cloud require administrators to define VPC and subnet ranges using CIDR notation, making it a foundational networking concept for hybrid and cloud-first environments.

Why does it matter for endpoint management with Hexnode

Modern endpoint management extends beyond devices to the networks they connect to. Hexnode UEM helps IT teams centrally manage enrolled endpoints, deploy policies, configure VPN settings, and monitor compliance across supported platforms.

By combining centralized device management with policy deployment and VPN configuration, Hexnode helps administrators manage enrolled endpoints across distributed work environments. This simplifies large-scale endpoint administration while supporting consistent security and compliance across corporate and remote devices.

CIDR and subnetting

Both are closely related, but they serve different networking objectives. CIDR is primarily used for flexible IP address allocation and route aggregation, while subnetting divides an IP network into smaller logical network segments.

It focuses on efficient IP allocation and internet routing, while subnetting divides an IP network into smaller logical network segments for easier management and improved performance.