IP Range Info: a beginner's guide

CIDR notation (Classless Inter-Domain Routing) is the standard way of writing a range of IP addresses as a single compact string — like `192.168.1.0/24`, `10.0.0.0/8`, or `2001:db8::/32`. CIDR was introduced in 1993 to replace an older system based on rigid "address classes" (Class A, Class B, Class C) that turned out to be incredibly wasteful of address space. Instead of being limited to those fixed sizes, CIDR lets you express any range as `<base address>/<number of bits in the prefix>`. The number after the slash is how many bits of the IP address are fixed; the rest of the bits can vary, and the variation is the size of the range.

You should care because almost every piece of network configuration on the internet uses CIDR notation — firewall rules, VPN definitions, BGP announcements, cloud-provider security groups, IP allowlists. Being unable to read CIDR is the same as being unable to read network notation in 2025. And the math is genuinely simple once you know the trick: a `/24` is the smallest commonly used range and contains 256 addresses; every step down from `/24` doubles the size; every step up halves it. A `/16` is 65,536 addresses; a `/8` is 16,777,216; a `/32` is exactly one address. Twenty minutes of practice and you can read any CIDR block at a glance.

The four things every CIDR notation explanation covers:

• The base address. The first address in the range. By convention, it has zeros in all the variable bits.

• The prefix length. The number after the slash. Higher numbers mean smaller ranges.

• The size of the range. Computed from the prefix length: a `/n` contains 2^(32-n) addresses for IPv4, or 2^(128-n) for IPv6.

• The broadcast and network addresses. The first and last addresses in the range have special meaning and are usually not assigned to hosts.

Three questions a CIDR explanation answers:

• How many IP addresses does this CIDR block actually contain?

• Does a particular IP address belong to a particular CIDR block?

• How do I write "all the addresses from X to Y" in CIDR notation?

The cost of not understanding CIDR is being locked out of every meaningful network conversation. The fix is one twenty-minute primer and then constant practice. CIDR is described in RFC 4632 for IPv4 and RFC 4291 for IPv6, and is one of the most stable, universal pieces of internet infrastructure.

In one sentence: Get CIDR (Classless Inter-Domain Routing) range details and ownership info

Returns detailed information about an IP (Internet Protocol address) address range specified in CIDR (Classless Inter-Domain Routing) notation. Calculates range boundaries, total usable addresses, network/broadcast addresses, and resolves ASN (Autonomous System Number) ownership, RIR allocation data, and abuse contact information.

Don't worry if some of the words above are still unfamiliar — there's a plain-language glossary at the bottom of this page, and most of the terms link to their own beginner guides if you want to learn more.

Here's what's actually happening behind the scenes when you call this endpoint:

Parses and validates CIDR (Classless Inter-Domain Routing) notation, then returns comprehensive range details: first/last IP (Internet Protocol address) addresses, total addresses in range, usable host count (excluding network and broadcast for IPv4 (Internet Protocol version 4)), network and broadcast addresses, subnet mask, wildcard mask, associated ASN (Autonomous System Number) with organization name, RIR allocation details (registry, date, status), and abuse contact email where available.

If you're using an AI assistant through MCP, you don't need to understand any of the technical details — the assistant calls the tool and translates the result for you.

Let's skip the marketing fluff and answer the only question that actually matters: why should you, a real human with a real to-do list, care about the IP Range Info tool? Here's the plain-English version, written the way you'd hear it from a friend who happens to do this for a living.

Essential for network planning, IP (Internet Protocol address) allowlist/blocklist management, and abuse handling. Understanding the scope and ownership of IP blocks prevents over-blocking in security rules, enables accurate capacity planning, and provides the right contacts for abuse reporting.

Picture this in real life. Imagine a network architect. Here's the situation they're walking into: Evaluate IP (Internet Protocol address) ranges for subnetting, peering decisions, or address space allocation by understanding exact range boundaries and available host count. Without the right tool, that person would be stuck copy-pasting between five browser tabs, reading documentation written for engineers, and crossing their fingers that the answer they cobble together is correct. With the IP Range Info tool, the same person gets a clear answer in seconds — no spreadsheets, no guessing, no waiting for someone on the infrastructure team to free up.

Three questions this tool answers in plain English. If any of these have ever crossed your mind, the IP Range Info tool is built for you:

• Where in the world is this server actually located, and who runs the network it sits on?

• How fast does traffic move between my users and my service?

• Is the IP address I am looking at part of a residential network, a data center, or something suspicious?

You can either click the tool and get the answer yourself, or ask your AI assistant — connected through MCP (Model Context Protocol) — to ask the question for you and translate the answer into something you can paste into Slack.

Who gets the most out of this. Network engineers, IT admins, sales teams qualifying enterprise prospects, and product teams building geo-personalization or fraud rules. If you see yourself in that list, this is one of the EdgeDNS tools you should bookmark today.

What happens if you skip this entirely. Skip it and you can't tell where your users actually are, who runs the network they're on, or why they're seeing slow page loads. That's why running this check — even once a month — is one of the cheapest forms of insurance you can give your domain.

If you're still on the fence about whether the IP Range Info tool belongs in your toolbox, this section is for you. Below you'll meet three real people — a network architect, a security operations, and a security engineer — facing three real situations where this tool turns a stressful afternoon into a five-minute task. Read whichever story sounds closest to your week.

Story 1: Network Capacity Planning

Imagine you're a network architect. Evaluate IP (Internet Protocol address) ranges for subnetting, peering decisions, or address space allocation by understanding exact range boundaries and available host count.

Why it matters: Make informed allocation decisions with precise range size calculations and ownership data.

Story 2: Abuse Report Routing

Imagine you're a security operations. Determine the correct organization and abuse contact for a malicious IP (Internet Protocol address) range to route incident reports and takedown requests.

Why it matters: Direct abuse reports to the responsible party with accurate ownership data and contact information.

Story 3: Blocklist Scope Assessment

Imagine you're a security engineer. Before adding a CIDR (Classless Inter-Domain Routing) block to a firewall blocklist, verify the range size and owner to avoid accidentally blocking legitimate traffic from shared hosting or CDN (Content Delivery Network) ranges.

Why it matters: Prevent over-blocking by understanding that a /16 contains 65,536 addresses vs a /24 with only 256.

Common situations across teams. Beyond the three stories above, here are the everyday workplace moments when people across the company reach for the IP Range Info tool — or one of the tools right next to it in this category. If any of these are on your calendar this month, that's your sign:

• When a customer reports that your site is slow specifically from their region.

• When you need to know whether traffic is coming from a residential network or a data center.

• When planning a CDN, points of presence, or geographic expansion.

• During an outage, to see exactly where in the route packets are getting lost.

If you can see yourself in even one of those bullets, the IP Range Info tool will pay for itself the first time you use it.

Still not sure? Here's the easiest test in the world. Open Claude, ChatGPT, Gemini, or any other AI assistant connected to the EdgeDNS MCP server and ask, in your own words: "Is the IP Range Info tool useful for my job?" The assistant will look at the tool, ask you a couple of follow-up questions about what you're trying to accomplish, and give you a straight answer in plain English. No commitment, no signup forms, no jargon.

If you've connected the EdgeDNS MCP server to Claude, ChatGPT, Gemini, Cursor, or any other AI assistant, you don't need to write any code. Just ask in plain English:

"Use the IP Range Info tool to check example.com and explain anything that looks wrong in plain language."

The AI will figure out which tool to call, fill in the right parameters, run it, and then explain the result back to you. No copy-pasting between tabs. No reading raw JSON. No memorizing endpoint names.

If you're a developer and want to call the endpoint from a script or your own application, here's the simplest possible example. Replace the placeholder API key with the real one from your dashboard.

There's just one piece of information you need to provide. The table below explains exactly what it is and what a real value looks like.

When you call this tool, you'll get back a JSON object with the fields below. If you're talking to it through an AI assistant, the assistant reads these for you and explains them in plain language — you don't need to memorize them.

These tools pair naturally with IP Range Info. If you're already running this check, the related ones often answer the next question that comes up:

• IP Geolocation — Get location, ASN, and org for an IP

• ASN Lookup — Get AS number, organization, and network type

• IP WHOIS — Get WHOIS registration data for an IP

If you're using an AI assistant through MCP (Model Context Protocol), you can ask it to run several of these in one go: "Check IP Range Info and the related tools for example.com and tell me what looks off."

If any words on this page felt like jargon, here's a plain-language version. Click any linked term to read a full beginner-friendly guide.

IP (Internet Protocol address) — A unique number that identifies a computer on the internet, like a phone number for a server.

CDN (Content Delivery Network) — A worldwide network of servers that store copies of your website close to your visitors so pages load fast.

ASN (Autonomous System Number) — A unique number assigned to a big network operator (like an ISP or cloud provider). Tells you who owns a chunk of the internet.

CIDR (Classless Inter-Domain Routing) — A shorthand way of describing a range of IP addresses, like 192.168.1.0/24. The number after the slash says how many addresses are in the range.

IPv4 (Internet Protocol version 4) — The original kind of internet address — four numbers separated by dots, like 203.0.113.10. The internet has run out of new ones, which is why IPv6 exists.