IPv4 in CIDR

ipv4-in-cidr · version 1.0.0 · URLs & IP addresses · free, no key needed

Test whether a canonical IPv4 address lies in a CIDR prefix whose host bits are zero.

Use when you need to: ipv4 in cidr · check ipv4 cidr membership · ipv4 address in network prefix.

Supported

• ipv4 in cidr
• check ipv4 cidr membership
• ipv4 address in network prefix

Not supported

• IPv6
• IPv4-mapped IPv6
• ranges with hyphens
• dotted netmasks
• host bits ignored

Behavior

• address is a canonical dotted-decimal IPv4 address (four octets 0-255, no leading zeros, no spaces, no hex).
• cidr is dotted-decimal/prefix with prefix a JSON-decimal integer 0-32 and no leading zeros except 0.
• The CIDR network address must have host bits zero; otherwise the tool throws CIDR host bits must be zero.
• inside is true iff the address uint32 is in [network, network + 2^(32-prefix) - 1].
• Prefix 32 matches only the address itself. Prefix 0 is valid only as 0.0.0.0/0 and matches every IPv4 address.
• network is the canonical dotted network address; prefix is a JSON integer.

Input

• address (string, required): max length 15; pattern ^(?:0|[1-9][0-9]{0,2})(?:\.(?:0|[1-9][0-9]{0,2})){3}$
• cidr (string, required): max length 18

Output

• inside (boolean, required)
• network (string, required): max length 15
• prefix (integer, required): min 0; max 32

Limits

• max address length: 15
• max cidr length: 18
• prefix min: 0
• prefix max: 32

Example

Request input:

{
  "address": "192.168.1.10",
  "cidr": "192.168.1.0/24"
}

Response:

{
  "result": {
    "inside": true,
    "network": "192.168.1.0",
    "prefix": 24
  }
}

How to call it

MCP

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

{
  "id": "ipv4-in-cidr",
  "version": "1.0.0",
  "input": {
    "address": "192.168.1.10",
    "cidr": "192.168.1.0/24"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/ipv4-in-cidr/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"address":"192.168.1.10","cidr":"192.168.1.0/24"}'

The machine-readable contract is at /v1/tools/ipv4-in-cidr/versions/1.0.0.

CLI

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

Get the client at /clients/cli/.

Related tools

• IPv6 in CIDR: Test whether an IPv6 address lies in a CIDR prefix whose host bits are zero.
• 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).
• IPv4 CIDR parse: Parse an IPv4 CIDR block into its network, broadcast, netmask, wildcard mask, usable host range and address counts.
• IPv4 range to cidrs: Convert an arbitrary IPv4 address range into the minimal list of CIDR blocks that exactly covers it.
• IPv4 address classify: Classify an IPv4 address against the static IANA IPv4 special-purpose address registry.