About this tool
What does it do?
It turns CIDR blocks and dash ranges into explicit address lists (and back into minimal CIDR sets) — for firewall rules, allowlists, scan scopes and inventory.
How to use it
- Enter CIDR (10.0.0.0/24) or range (10.0.0.5–10.0.0.20).
- Copy the expanded list or collapsed CIDR form.
- Feed directly into firewall, scanner or spreadsheet.
Examples
- Expanding a /24 into 254 allowlist entries.
- Collapsing scattered IPs into minimal CIDR blocks for a WAF.
- Generating scan targets for an approved assessment.
Important limitations
- Big blocks explode: a /16 is 65,536 lines — paginate or script beyond /22 or so.
- Expansion loses the “why” — keep the original CIDR as documentation.
- Only scan what you own or are authorized to test.
Privacy
Local computation. Target lists reveal infrastructure — they stay in your browser.
Frequently asked questions
How many IPs in a /24?
256 total, 254 usable (network + broadcast reserved).
Collapse or expand?
Expand for per-IP tooling, collapse for humans and firewalls.
IPv6?
Ranges are astronomically large — use the IPv6 tools with prefixes, never expansion.
Related tools
IPv4 subnet calculator · IPv4 address converter · Random port generator