CIDR Route Summarization

Important

Migrate to route-summarization-rs. aggregate-cidr is a Rust rewrite of this script with the same options, no Perl or module dependencies, and this version's quirks fixed. It also adds --exclude for removing addresses from the output. New deployments should use it, and existing ones can switch with a symlink: Migrating from the Perl version. This script is kept for existing installs and as the fallback in the projects below.

A lightweight CIDR aggregation utility built in Perl using the Net::CIDR::Lite module. This tool summarizes IPv4 and IPv6 prefixes from standard input and optionally formats output for SPF record usage.

Inspired by the original concept described by Adrian Popa in Random Thoughts; see LICENSE for how that attribution is handled.

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Features

• Summarizes IPv4 and IPv6 CIDR prefixes
• Accepts plain IPs (auto-converted to /32 or IPv6 host equivalents)
• Supports SPF-style ip4: / ip6: prefix stripping and output
• Gracefully ignores invalid prefixes
• Simple STDIN-driven workflow for pipelines and scripts

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Usage

Run interactively:

$ ./aggregateCIDR.pl
# One IP/CIDR per line, e.g. 1.2.3.0/24 -- press CTRL+D when done.

Or pipe a file into it:

$ ./aggregateCIDR.pl < cidr.txt

Options

--help        Display usage information
--quiet       Suppress non-essential messages
--spf         Enable SPF input parsing and SPF-style output

Example with SPF mode:

$ ./aggregateCIDR.pl --spf < spf-list.txt
ip4:203.0.113.0/24
ip6:2001:db8::/48

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Input Examples

192.0.2.1
192.0.2.0/24
2001:db8:10::/48
ip4:198.51.100.0/25   (with --spf)

Invalid or non-CIDR lines are ignored.

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Output

The script prints an aggregated list of CIDRs with redundant or overlapping ranges collapsed. IPv4 host addresses (/32) are printed without the mask unless explicitly required.

Example:

192.0.2.0/24
198.51.100.0/24
2001:db8:10::/48

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Project Integrations

Because this tool consumes input exclusively from STDIN, it embeds cleanly into other automation frameworks such as Bash, Tcl, Python, CI pipelines, Makefile workflows, or any scripting environment.

Projects using or compatible with this tool

• Postwhite Fork — https://github.com/nabbi/postwhite
• TCL IPSet — https://github.com/nabbi/tcl-ipset

Both now run aggregate-cidr when it is on PATH and fall back to this script, so installing the Rust version is all the migration they need.

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Requirements

• Perl 5
• Net::CIDR::Lite module
• Getopt::Long (core Perl)

Install module via CPAN:

cpan install Net::CIDR::Lite

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License

MIT — see LICENSE. The original blog post that inspired this script's control flow carries no license of its own; see the LICENSE file for how that's handled.

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