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.