IPv4 Range Expander
Enter a start and end IPv4 address to calculate the covering CIDR block, subnet mask, and usable host ranges.
Range Quick Overview
How IP Range Expansion Works
Learn how arbitrary start and end IP configurations translate into valid CIDR blocks.
When network administrators analyze firewall logs, DHCP allocations, or security blacklists, they often encounter arbitrary start and end IP address ranges. The IPv4 Range Expander determines the tightest matching CIDR block (Classless Inter-Domain Routing) that fully encompasses the input range by analyzing the binary difference between the start and end addresses.
Covering Block Calculation
Automatically calculates the smallest subnet mask and prefix length needed to cover your custom range.
Subnet & Wildcard Masks
Instantly outputs standard dotted-decimal subnet masks along with inverse wildcard masks used in ACL configurations.
Usable Host Breakdown
Identifies network addresses, broadcast addresses, and the valid assignable host range for equipment deployment.
100% Secure & Private
Calculations execute entirely inside your browser via local JavaScript. No IP data is stored or transferred.
One-Click Copy Support
Easily copy specific metrics or export the complete set of parameters with visual feedback confirmation.
Real-Time Evaluation
Results update dynamically as you type or change input range values for seamless workflow efficiency.