CIDR Subtraction & Exclusion Tool

Carve out an excluded CIDR block from a base subnet and compute the remaining non-overlapping CIDR pieces.

How It Works & Processing Standards

Carve out an excluded CIDR block from a base subnet and compute the remaining non-overlapping CIDR pieces.

Your input data is never sent to any server and is securely processed on your device.

Current Limits

  • Maximum input length: 100,000 characters

CIDR Subtraction & Exclusion Tool is a 100% free, browser-based online utility. All calculations and file conversions run locally inside your browser (Local-First) without sending data to remote servers, keeping your documents and inputs strictly private.

How to Use CIDR Subtraction & Exclusion Tool

  1. 1
    Provide Base & Exclude BlocksEnter base CIDR and the subnet to subtract.
  2. 2
    View Remaining PiecesCopy the resulting list of remaining valid CIDRs.

Common Use Cases

  • Carving out DMZ subnets from enterprise VPCs and reserving IP ranges for VPN tunnels
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