Subnet Calculator

v2.6.0
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Supernet & Route Summarisation
?Finds the smallest single CIDR block that contains all of the listed CIDRs. Useful for aggregating routes into a single summary route. ?Computes the minimal set of non-overlapping CIDRs that exactly covers the listed networks. Unlike Find Supernet, this avoids including addresses outside the input ranges.
IP Range → CIDR?Enter a start and end IPv4 address to get the minimal set of CIDR blocks that exactly covers that range using the greedy largest-aligned-block algorithm.
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Subnet Allocation Tree
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IPv6 ULA Prefix Generator (RFC 4193)
Name Hosts Needed
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Save & Restore Session?Saves your VLSM inputs to the server so you can restore them later via a short link. Sessions expire after the configured TTL. No account required.

Saved sessions expire after 365 days.

Subnet Overlap Checker?Compares two CIDRs and reports whether they overlap, one contains the other, are identical, or have no relationship. Supports both IPv4 and IPv6.
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Multi-CIDR Overlap Check?Enter up to 50 IPv4 or IPv6 CIDRs, one per line. The tool reports any pairs that overlap, are identical, or where one contains the other.
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