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Networking Intermediate

What is CIDR Notation?

A compact method for specifying IP addresses and their associated routing prefix using a slash followed by the prefix length.

CIDR (Classless Inter-Domain Routing) notation represents IP ranges: 192.168.1.0/24 means the first 24 bits are the network portion, leaving 8 bits (256 addresses) for hosts. /32 is a single IP, /16 is 65,536 addresses.

Common ranges: /8 (16.7M addresses), /16 (65,536), /24 (256), /28 (16), /32 (1 host). CIDR replaced classful networking (Class A/B/C) and enables efficient IP allocation. Understanding CIDR is essential for VPC design, security groups, and firewall rules.

Related Terms

DNS (Domain Name System)
A hierarchical naming system that translates human-readable domain names into IP addresses.
Network Topology
The physical or logical arrangement of nodes and connections in a computer network, such as star, mesh, ring, or bus configurations.
NAT (Network Address Translation)
A method of mapping private IP addresses to public IP addresses, allowing multiple devices to share a single public IP.
Overlay Network
A virtual network built on top of an existing physical network, enabling features like container networking and VPNs.
OSI Model
The seven-layer Open Systems Interconnection model that standardizes network communication functions from physical transmission to application protocols.
DNS Propagation
The time it takes for DNS record changes to spread across all DNS servers worldwide, typically taking up to 48 hours.
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