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Networking tools.

Subnet, CIDR, IP and DNS calculators that do exact 32- and 128-bit math in your browser.

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Networking tools

  • NetworkingLive

    Subnet Calculator

    Network, broadcast, mask and host range from any IPv4/IPv6 CIDR.

    Enter an IPv4 or IPv6 address with a prefix and get the network and broadcast addresses, netmask, wildcard, usable host range and address counts. Pure client-side.

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  • NetworkingLive

    IP Address Converter

    Convert an IP between dotted decimal, integer, hex and binary.

    Paste an IPv4 or IPv6 address in any form — dotted decimal, integer, hexadecimal or binary — and see every representation at once. Pure client-side.

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  • NetworkingLive

    CIDR / Subnet Checker

    Check an IP against CIDR ranges, find overlaps, and merge lists.

    Paste an IP plus CIDRs — or a whole list — to check membership, spot overlapping or contained ranges, and get the minimal covering set. Pure client-side.

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  • NetworkingLive

    MAC Address Formatter

    Reformat a MAC across colon, hyphen, Cisco and bare — and read its bits.

    Paste a MAC address and get it normalised across colon, hyphen, Cisco dotted and bare forms, plus the U/L and I/G bit meaning, OUI and the EUI-64 IPv6 link-local address it derives. Pure client-side.

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  • NetworkingLive

    Reverse DNS / PTR Helper

    Build the in-addr.arpa / ip6.arpa PTR name and reverse zone for any IP.

    Enter an IPv4 or IPv6 address or CIDR and get the in-addr.arpa or ip6.arpa PTR name, the matching reverse zone and the nibble breakdown behind it. Pure client-side.

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  • NetworkingLive

    Subnet Splitter

    Split a parent CIDR into subnets and find the free space around allocations.

    Split a parent IPv4 or IPv6 CIDR into equal subnets or carve it up with VLSM, then list existing allocations to find the gaps and the next available subnet. Pure client-side.

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When you reach for Networking tools.

Subnetting is the arithmetic everyone does under pressure and nobody does twice the same way. You are mid-incident, someone asks whether 10.20.4.0/22 overlaps the VPC CIDR you allocated last quarter, and the honest answer is that you are about to count in binary on a napkin.

The mistakes are predictable. Off-by-one on the broadcast address. Forgetting that a /31 has no usable hosts in the classic model but is legal for point-to-point links. Assuming IPv6 behaves like IPv4 with longer numbers, when the host counts are large enough that ordinary JavaScript numbers silently lose precision.

These tools do the maths exactly. Every calculation runs on BigInt, so a /8 in IPv4 and a /48 in IPv6 are equally correct — no float rounding, no truncation at 2^53. Parsers return a specific reason when input is rejected ("Octet 256 is greater than 255") rather than a generic failure, because during an incident "invalid" is not a useful answer.

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