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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.

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