CIDR Tools

A small but heavily-used utility category. The CIDR tools normalise, expand, and classify IP networks — useful as the first step before any bulk-paste run against the network tools.

Three tools live here:

• CIDR Calculator — facts about a single CIDR.
• IP Range Expander — flatten a CIDR into individual IPs.
• Mask preview — visualise the bit boundaries of a netmask.

CIDR Calculator

Input a CIDR block. The tool returns:

The classification chip is the most immediately useful field — it tells you whether the CIDR is something you care about (public address space) or something you do not (private, link-local, loopback, multicast).

IP Range Expander

Input a CIDR block (or a start-end range). The tool returns a flat list of every IP in the range, with optional filters:

• Drop network and broadcast addresses.
• IPv4 only / IPv6 only.
• Limit count (caps very large ranges to a configurable maximum).

The expanded list exports as:

• Plain text, one IP per line.
• CSV.
• Nmap target file (.nmap).
• Hosts file fragment.

This is the input you feed into a bulk-paste run against IP geolocation, reverse DNS, or IP reputation.

Per-IP rDNS pass

After expanding a range, you can optionally run per-IP reverse DNS in parallel (with bounded concurrency). This is the "interesting hosts inside an unknown range" pattern — most IPs return no PTR, the ones that do tell you what the operator wanted to publish.

Grouped /24 view

For larger expansions, the tool offers a grouped by /24 view that shows one row per /24 inside the original range, with the count of "interesting" IPs (those with a PTR or other signal). Helpful for narrowing where to actually look.

Pivots

Bulk CIDR

Bulk paste accepts multiple CIDRs and returns the calculator output for each in an aggregate table — useful when you have a stack of network blocks to classify quickly.

Sources

• All CIDR math runs locally. No external sources are queried.
• Per-IP rDNS pass uses the system DNS resolver.