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CIDR to IP Range Converter

Enter a CIDR block to see its first and last address, netmask and total count.

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What this tool does

CIDR (Classless Inter-Domain Routing) notation writes an IP range compactly as an address plus a prefix length, like 10.0.0.0/24. This converter expands that block into its first and last IP addresses, the equivalent netmask, and the total number of addresses it covers.

Example

10.0.0.0/24 covers 10.0.0.0 through 10.0.0.255 — 256 addresses with netmask 255.255.255.0.

Common uses

  • Writing firewall and security-group rules.
  • Planning IP allocations for networks and VPCs.
  • Understanding allow/deny lists expressed in CIDR.

Limitations

  • IPv4 only. Prefixes from /0 to /32 are supported.
  • For usable-host counts and broadcast details, see the full subnet calculator.
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