IPv6 in CIDR

ipv6-in-cidr · version 1.0.0 · URLs & IP addresses · free, no key needed

Test whether an IPv6 address lies in a CIDR prefix whose host bits are zero.

Use when you need to: ipv6 in cidr · check ipv6 cidr membership · ipv6 address in network prefix.

Supported

• ipv6 in cidr
• check ipv6 cidr membership
• ipv6 address in network prefix

Not supported

• IPv4
• zone/scope IDs

Behavior

• address accepts any RFC 4291 textual form (see ipv6-parse).
• cidr is address/prefix with prefix a canonical decimal integer 0-128 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 address's 128-bit value is in [network, network + 2^(128-prefix) - 1].
• network is the RFC 5952 canonical network address; prefix is a JSON integer.

Input

• address (string, required): max length 45
• cidr (string, required): max length 49

Output

• inside (boolean, required)
• network (string, required): max length 45
• prefix (integer, required): min 0; max 128

Limits

• max address length: 45
• max cidr length: 49
• prefix min: 0
• prefix max: 128

Example

Request input:

{
  "address": "2001:db8::10",
  "cidr": "2001:db8::/32"
}

Response:

{
  "result": {
    "inside": true,
    "network": "2001:db8::",
    "prefix": 32
  }
}

How to call it

MCP

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

{
  "id": "ipv6-in-cidr",
  "version": "1.0.0",
  "input": {
    "address": "2001:db8::10",
    "cidr": "2001:db8::/32"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/ipv6-in-cidr/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"address":"2001:db8::10","cidr":"2001:db8::/32"}'

The machine-readable contract is at /v1/tools/ipv6-in-cidr/versions/1.0.0.

CLI

node cli.mjs run ipv6-in-cidr 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• IPv4 in CIDR: Test whether a canonical IPv4 address lies in a CIDR prefix whose host bits are zero.
• IPv6 CIDR contains: Test whether one IPv6 CIDR block fully contains another IPv6 CIDR block.
• IPv6 CIDR overlap: Test whether two IPv6 CIDR blocks overlap (share at least one address).
• IPv6 CIDR parse: Parse an IPv6 CIDR block into its canonical network address, prefix, first/last address, and total address count.
• IPv6 range to cidrs: Convert an arbitrary IPv6 address range into the minimal list of CIDR blocks that exactly covers it.
• IPv4 CIDR contains: Test whether one IPv4 CIDR block fully contains another IPv4 CIDR block.