Subnet Calculator — Free Online IPv4 Subnet Mask Calculator
Calculate subnet mask, network address, broadcast address, host range, and usable hosts from an IP/CIDR.
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IPv4 Subnetting: Dividing Networks into Manageable Segments
Subnetting is the process of dividing an IP network into smaller subnetworks. It's fundamental to network design — allowing organizations to segment traffic by department, function, or security zone while efficiently using IP address space. Every network engineer, DevOps professional, and cloud architect needs to understand subnetting.
CIDR notation (e.g., 192.168.1.0/24) encodes both the network address and the subnet mask in a compact format. The prefix length (/24) specifies how many bits belong to the network — the remaining bits are available for host addresses. A /24 gives 256 total addresses with 254 usable (network and broadcast are reserved).
Cloud providers (AWS VPC, Azure Virtual Network, GCP VPC) all use CIDR notation for subnet definition. Kubernetes pods and services use CIDR ranges. Firewall rules reference CIDR blocks. This calculator provides all the subnet details needed for network planning, firewall configuration, and cloud infrastructure.
Standards & References
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