Is this IP in that CIDR range?

Paste a list of IPs or CIDRs — one per line — and it does four things: answers whether a bare IP falls inside any CIDR in the list, aggregates the entries into the minimal set of CIDR blocks that exactly covers the same addresses, reports every overlap and containment between them, and shows a parsed, normalised breakdown of each line. Everything runs in your browser.

Type the IP on one line and the CIDR range — or several — on the lines below. The verdict card answers immediately: 10.0.0.5 is inside 10.0.0.0/24, because that block spans 10.0.0.0 through 10.0.0.255. A bare IP (no /prefix) is compared against every CIDR in the list, and every range that contains it is named, most specific first. If nothing contains it, the tool says so explicitly. Coming from the IP Address Converter? The "Check against CIDRs" link pre-fills the IP for you.

No. Parsing, comparison and aggregation all run 100% client-side in your tab — no server, no account, no logging. You can safely paste internal allow-lists and route tables.

Aggregation (also called summarisation or supernetting) replaces several adjacent or overlapping blocks with the fewest CIDRs that cover exactly the same addresses — for example 192.168.0.0/24 through 192.168.3.0/24 collapses to a single 192.168.0.0/22. It shortens firewall rules and route tables without changing what they match.

Containment means one block sits entirely inside another (10.0.5.0/24 is inside 10.0.0.0/16). A plain overlap means two blocks share some addresses without one fully enclosing the other. The checker labels each relationship — equal, contains, inside, or overlaps — so you can spot redundant or conflicting entries.

Yes. IPv4 and IPv6 entries are parsed together; comparison and aggregation are done within each family (a v4 block and a v6 block never overlap), and the minimal covering set is reported per family using full 128-bit precision for IPv6.

One IP or CIDR per line. A bare address is treated as a /32 (or /128). Blank lines and lines starting with # are ignored, so you can paste a commented config block directly. Anything that is not a valid IP or CIDR is flagged rather than silently dropped.

Each CIDR is converted to its first and last address as a numeric range. Two CIDRs overlap when their ranges share any address — even a single one. Paste your list into the tool and every overlapping or contained pair is labelled automatically, distinguishing equal blocks, one-inside-the-other (containment), and partial overlaps.

Paste the full list and the tool sorts the entries, merges adjacent and overlapping ranges into contiguous numeric intervals, then re-splits each interval into the fewest aligned CIDR blocks that cover it exactly. The result is the smallest possible set of CIDRs that still covers every address in the original list — useful for shrinking routing tables, firewall rules, and BGP prefix lists.

AWS rejects VPC peering, Transit Gateway attachments, and VPN connections when any CIDR ranges overlap. Paste all VPC and subnet CIDRs into the checker before deploying: it flags every overlapping or contained pair so you can re-plan address space ahead of time. Because everything runs in the browser, no internal IP data is uploaded.

Subnetting splits one block into smaller subnets by lengthening the prefix — for example /24 into eight /27s. Supernetting, also called CIDR aggregation or route summarization, is the reverse: it merges multiple contiguous blocks into one larger block by shortening the prefix — for example eight /27s back into a single /24. Aggregation reduces routing-table size and firewall-rule count while preserving full address coverage.