IPv6 Range to CIDR
Represent an IPv6 range as CIDR blocks.
An arbitrary address range rarely lines up with a single CIDR prefix, so it has to be expressed as several. This finds the smallest set of IPv6 CIDR blocks covering the range exactly — no more and no fewer addresses.
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How IPv6 Range to CIDR works
What it does
Represent an IPv6 range as CIDR blocks.
What you get
CIDR blocks that cover the supplied IPv6 range.
On your device
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What if a check cannot finish?
Confirm your input and try again. A timeout, blocked request, or unavailable provider is not proof that a domain is broken. Internet measurements and third-party services have limits.
IPv6 Range to CIDR — frequently asked questions
Why does one range produce several blocks?
CIDR blocks must start on a power-of-two boundary. A range beginning or ending mid-boundary can only be covered by combining differently sized blocks.
Can I just use one bigger block instead?
You can, but it would include addresses outside your range. In a firewall rule that means permitting or blocking more than you intended.
Does the order of the blocks matter?
Not for coverage. Most rule engines evaluate them independently, though some match first-hit — check your platform's semantics.