Question 1

How does the CIDR aggregator work?

Accepted Answer

Each input line (single IP, dashed range a.b.c.d-e.f.g.h, or CIDR block) is converted into a [start, end] numeric interval — IPv4 as a 32-bit BigInt and IPv6 as a 128-bit BigInt. The intervals are sorted, overlapping and adjacent intervals are merged into the smallest covering set, and each merged interval is greedily decomposed back into the minimal set of aligned CIDR prefixes (the same algorithm used by iprange-to-cidr / Python netaddr).

Question 2

Does it support both IPv4 and IPv6?

Accepted Answer

Yes. The tool detects the family of each line automatically (':' → IPv6, otherwise IPv4), parses with full IPv6 '::' compression and embedded-IPv4 support, and aggregates IPv4 and IPv6 separately — you'll get two output sections (or only one if all inputs are the same family). BigInt is used throughout so huge ranges like 0.0.0.0/0 or ::/0 are counted mathematically without enumerating every address.

Question 3

How do exclusions (subtractions) work?

Accepted Answer

Enter exclusion blocks on a separate line or in the exclusion box. The tool subtracts their intervals from the aggregated set — a single large block may be split into several smaller CIDRs around the excluded hole, exactly like a firewall rule that says 'allow this big network except this small slice'. The before/after counts reflect the post-exclusion totals.

Question 4

What export formats are supported?

Accepted Answer

Five formats: CIDR list (one prefix per line), IP ranges (start-end per line), Cisco ACL (`access-list ... permit ip any`), pfSense alias (a `network` alias body, one CIDR per line), and nginx (`allow ;` directives). All formats handle IPv4 and IPv6 and are copy/download ready.

Question 5

What extra features does this tool have versus other CIDR aggregators?

Accepted Answer

(1) Mixed input — IPs, dashed ranges, and CIDRs in one paste. (2) Full IPv6 support with BigInt math. (3) Optional exclusion/subtraction that splits blocks correctly. (4) Before/after prefix and address counts with addresses-saved badge. (5) Five export formats (CIDR, ranges, Cisco ACL, pfSense alias, nginx allow). (6) Per-line parse errors collected and shown with line numbers. (7) CIDR ↔ range expansion both ways. (8) History (localStorage, last 20). (9) Shareable URL encoding input + exclusions. (10) Sort/normalize mode. (11) Address count via BigInt (handles /0 and ::/0 without overflow). (12) 100% client-side — your IP lists never leave the browser.

CIDR Aggregator & Network Summarizer

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