IPv4 mask convert

ipv4-mask-convert · version 1.0.0 · URLs & IP addresses · free, no key needed

Convert between an IPv4 prefix length, dotted subnet netmask, and dotted wildcard (host) mask.

Use when you need to: ipv4 mask convert · prefix to netmask · netmask to prefix.

Supported

• ipv4 mask convert
• prefix to netmask
• netmask to prefix
• wildcard mask convert
• subnet mask calculator

Not supported

• IPv6
• non-contiguous masks

Behavior

• Input is exactly one of prefix, netmask, or wildcard; unknown fields and multiple/zero of these three throw.
• prefix is a JSON integer 0-32.
• netmask must be a contiguous run of 1-bits from the most significant bit followed by 0-bits (a valid subnet mask); otherwise the tool throws.
• wildcard is the bitwise complement of a valid netmask (a contiguous run of 0-bits followed by 1-bits); otherwise the tool throws.
• Output always includes all three equivalent representations.

Input

• object

Output

• prefix (integer, required): min 0; max 32
• netmask (string, required): max length 15
• wildcard (string, required): max length 15

Limits

• prefix min: 0
• prefix max: 32

Example

Request input:

{
  "prefix": 24
}

Response:

{
  "result": {
    "prefix": 24,
    "netmask": "255.255.255.0",
    "wildcard": "0.0.0.255"
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "ipv4-mask-convert",
  "version": "1.0.0",
  "input": {
    "prefix": 24
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/ipv4-mask-convert/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"prefix":24}'

The machine-readable contract is at /v1/tools/ipv4-mask-convert/versions/1.0.0.

CLI

node cli.mjs run ipv4-mask-convert 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• IPv4 CIDR parse: Parse an IPv4 CIDR block into its network, broadcast, netmask, wildcard mask, usable host range and address counts.
• IPv4 prefix for hosts: Compute the smallest IPv4 CIDR block (largest prefix length) whose usable host capacity meets a required count.
• IPv4 range to cidrs: Convert an arbitrary IPv4 address range into the minimal list of CIDR blocks that exactly covers it.
• IPv4 address offset: Add a signed integer offset to an IPv4 address, throwing if the result leaves the IPv4 address space.
• IPv4 CIDR contains: Test whether one IPv4 CIDR block fully contains another IPv4 CIDR block.
• IPv4 CIDR overlap: Test whether two IPv4 CIDR blocks overlap (share at least one address).