IPv6 range to cidrs

ipv6-range-to-cidrs · version 1.0.0 · URLs & IP addresses · free, no key needed

Convert an arbitrary IPv6 address range into the minimal list of CIDR blocks that exactly covers it.

Use when you need to: ipv6 range to cidr · convert ipv6 range to cidrs · summarize ipv6 address range.

Supported

• ipv6 range to cidr
• convert ipv6 range to cidrs
• summarize ipv6 address range

Not supported

• IPv4
• hyphenated single-string ranges

Behavior

• first_address and last_address accept any RFC 4291 textual form (see ipv6-parse); first_address must not exceed last_address as a 128-bit value.
• cidrs is the minimal ordered list of non-overlapping CIDR blocks (largest-first at each step) whose union is exactly [first_address, last_address].
• A single address (first_address equal to last_address) yields one /128 block.

Input

• first_address (string, required): max length 45
• last_address (string, required): max length 45

Output

• cidrs (array of string, required): max items 256; each max length 49
• count (integer, required): min 1; max 256

Limits

• max address length: 45
• max output blocks: 256

Example

Request input:

{
  "first_address": "2001:db8::9",
  "last_address": "2001:db8::b"
}

Response:

{
  "result": {
    "cidrs": [
      "2001:db8::9/128",
      "2001:db8::a/127"
    ],
    "count": 2
  }
}

How to call it

MCP

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

{
  "id": "ipv6-range-to-cidrs",
  "version": "1.0.0",
  "input": {
    "first_address": "2001:db8::9",
    "last_address": "2001:db8::b"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/ipv6-range-to-cidrs/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"first_address":"2001:db8::9","last_address":"2001:db8::b"}'

The machine-readable contract is at /v1/tools/ipv6-range-to-cidrs/versions/1.0.0.

CLI

node cli.mjs run ipv6-range-to-cidrs 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• IPv4 range to cidrs: Convert an arbitrary IPv4 address range into the minimal list of CIDR blocks that exactly covers it.
• IPv6 address offset: Add a signed integer offset to an IPv6 address, throwing if the result leaves the IPv6 address space.
• IPv6 CIDR aggregate: Merge a list of IPv6 CIDR blocks into the minimal equivalent list of non-overlapping CIDR blocks.
• IPv6 CIDR parse: Parse an IPv6 CIDR block into its canonical network address, prefix, first/last address, and total address count.
• IPv6 in CIDR: Test whether an IPv6 address lies in a CIDR prefix whose host bits are zero.
• IPv6 parse: Parse an IPv6 address (any RFC 4291 textual form) into its 8 hextets and a 128-bit integer string.