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Range to CIDR

Convert a start and end IPv4 or IPv6 address into the smallest set of covering CIDR blocks.

What this tool does

Range to CIDR converts a start and end IP address into the smallest set of CIDR blocks that covers that exact range.

It is useful when a vendor gives you raw IP ranges but your firewall, router, cloud rule, or API expects CIDR notation. For smaller network slices, use the subnet splitter.

CIDR notation explained Understand why multiple CIDR blocks may be needed for one range. CIDR calculator Inspect one network block in detail. Subnet splitter Split an existing network into fixed child prefixes. IP in CIDR Test whether an address falls inside a CIDR block.