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ohernandez-dev-blossom

Cidr Calc

by Omar Hernandez · GitHub ↗ · v1.0.0 · MIT-0
cross-platform ✓ Security Clean
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Install in OpenClaw
/install cidr-calc
Description
Calculate subnet information from CIDR notation. Use when the user asks to calculate a subnet, find the network address, broadcast address, host range, subne...
README (SKILL.md)

CIDR Calculator

Given an IP address in CIDR notation, compute all subnet parameters: network address, broadcast, host range, subnet mask, wildcard mask, host counts, IP class, and binary representation.

Input

  • A CIDR notation string in the format A.B.C.D/N (e.g. 192.168.1.0/24)

Output

A structured result with these fields:

  • CIDR Notation (normalized)
  • Network Address
  • Broadcast Address
  • Subnet Mask
  • Wildcard Mask
  • First Usable Host
  • Last Usable Host
  • Total Hosts (2^(32-N))
  • Usable Hosts
  • IP Class (A / B / C / D Multicast / E Reserved)
  • Network Type (Private / Public)
  • Binary Representation of the IP

Instructions

  1. Validate the input. It must match \d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\/\d{1,2}. Each octet must be 0–255. Prefix must be 0–32.
  2. Compute values using standard subnet math:
    • maskNum = (0xFFFFFFFF \x3C\x3C (32 - prefix)) >>> 0
    • wildcardNum = ~maskNum >>> 0
    • networkNum = (ipNum & maskNum) >>> 0
    • broadcastNum = (networkNum | wildcardNum) >>> 0
    • totalHosts = 2^(32 - prefix)
    • usableHosts: if prefix == 32 → 1; if prefix == 31 → 2; else totalHosts - 2
  3. Determine IP class from first octet:
    • 1–126 → A; 128–191 → B; 192–223 → C; 224–239 → D (Multicast); 240–255 → E (Reserved); 127 → Loopback
  4. Determine private vs public:
    • Private: 10.x.x.x, 172.16–31.x.x, 192.168.x.x, 127.x.x.x (loopback)
  5. Compute binary as four 8-bit groups joined by dots.
  6. Present results in a clear labeled format.

Quick CIDR reference

CIDR Subnet Mask Total Hosts
/8 255.0.0.0 16,777,216
/16 255.255.0.0 65,536
/20 255.255.240.0 4,096
/22 255.255.252.0 1,024
/24 255.255.255.0 256
/28 255.255.255.240 16
/30 255.255.255.252 4
/32 255.255.255.255 1

Options

  • Input is always a single CIDR string; no additional options.

Examples

Input: 192.168.1.0/24

Output:

CIDR Notation:   192.168.1.0/24
Network Address: 192.168.1.0
Broadcast:       192.168.1.255
Subnet Mask:     255.255.255.0
Wildcard Mask:   0.0.0.255
First Host:      192.168.1.1
Last Host:       192.168.1.254
Total Hosts:     256
Usable Hosts:    254
IP Class:        C
Network Type:    Private
Binary:          11000000.10101000.00000001.00000000

Input: 10.0.0.0/8

Output:

CIDR Notation:   10.0.0.0/8
Network Address: 10.0.0.0
Broadcast:       10.255.255.255
Subnet Mask:     255.0.0.0
Wildcard Mask:   0.255.255.255
First Host:      10.0.0.1
Last Host:       10.255.255.254
Total Hosts:     16,777,216
Usable Hosts:    16,777,214
IP Class:        A
Network Type:    Private
Binary:          00001010.00000000.00000000.00000000

Error Handling

  • If the input is not valid CIDR notation, say so and provide the expected format (A.B.C.D/N).
  • If an octet exceeds 255 or the prefix exceeds 32, explain the validation error.
  • If the user provides an IP without a prefix (e.g. 192.168.1.1), ask for the prefix length or assume /32.
Usage Guidance
This appears safe and coherent for computing subnet details. You can install it without exposing credentials or installing extra software. Before relying on it for critical tasks, test its outputs on edge cases (e.g., 0.0.0.0, 255.255.255.255, /31, /32) and note the documented mistake treating 127.x.x.x as a private network (it is loopback). If you need authoritative behavior for unusual prefixes, verify against a trusted networking tool or library.
Capability Analysis
Type: OpenClaw Skill Name: cidr-calc Version: 1.0.0 The skill bundle provides instructions for an AI agent to perform standard CIDR subnet calculations, including network/broadcast addresses and host ranges. The logic in SKILL.md is purely mathematical and descriptive, with no evidence of data exfiltration, malicious execution, or prompt injection attacks.
Capability Assessment
Purpose & Capability
Name and description match the SKILL.md instructions: the skill only describes validating CIDR input and computing subnet parameters. It does not request unrelated binaries, environment variables, or installs.
Instruction Scope
Instructions stay within the expected scope (validation, subnet math, class and private/public determination, binary output). One minor correctness issue: the SKILL.md lists 127.x.x.x as Private — 127.0.0.0/8 is loopback/host-local, not a private RFC1918 network. Also check edge cases (0.0.0.0, 255.255.255.255, /31 and /32 semantics) if you rely on this for production use.
Install Mechanism
No install spec and no code files — instruction-only skill. Nothing will be written to disk or downloaded during install.
Credentials
Requires no environment variables, credentials, or config paths — the declared requirements are minimal and appropriate for a local calculation utility.
Persistence & Privilege
always is false and the skill does not request persistent or elevated platform privileges. Autonomous invocation is allowed by default but not combined with any sensitive access.
How to Use
  1. Make sure OpenClaw is installed (local or Docker)
  2. Run the install command in chat: /install cidr-calc
  3. After installation, invoke the skill by name or use /cidr-calc
  4. Provide required inputs per the skill's parameter spec and get structured output
Version History
v1.0.0
Initial release of cidr-calc: Calculate subnet details from CIDR notation. - Computes network address, broadcast address, host range, subnet mask, wildcard mask, total/usable hosts, IP class, network type, and binary representation. - Accepts a single IP in CIDR notation (e.g., 192.168.1.0/24) and outputs a clear, structured table. - Validates input format and provides helpful error messages for invalid entries. - Distinguishes between private, public, loopback, and special-use IP ranges. - Includes example inputs, expected output, and a quick CIDR reference chart.
Metadata
Slug cidr-calc
Version 1.0.0
License MIT-0
All-time Installs 0
Active Installs 0
Total Versions 1
Frequently Asked Questions

What is Cidr Calc?

Calculate subnet information from CIDR notation. Use when the user asks to calculate a subnet, find the network address, broadcast address, host range, subne... It is an AI Agent Skill for Claude Code / OpenClaw, with 144 downloads so far.

How do I install Cidr Calc?

Run "/install cidr-calc" in the OpenClaw or Claude Code chat to install it in one step — no extra setup required.

Is Cidr Calc free?

Yes, Cidr Calc is completely free, licensed under MIT-0. You can download, install and use it at no cost.

Which platforms does Cidr Calc support?

Cidr Calc is cross-platform and runs anywhere OpenClaw / Claude Code is available (cross-platform).

Who created Cidr Calc?

It is built and maintained by Omar Hernandez (@ohernandez-dev-blossom); the current version is v1.0.0.

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