# IPv6 CIDR parse

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

Parse an IPv6 CIDR block into its canonical network address, prefix, first/last address, and total address count.

**Use when you need to: ipv6 cidr parse · ipv6 subnet info · ipv6 cidr to network details.**

## Supported

- ipv6 cidr parse
- ipv6 subnet info
- ipv6 cidr to network details

## Not supported

- IPv4
- host-address CIDR notation (host bits must be zero)
- subnet-router anycast/usable-host distinctions

## Behavior

- cidr is address/prefix (address in any RFC 4291 textual form) with prefix a canonical decimal integer 0-128 and no leading zeros except 0.
- The network address must have host bits zero; otherwise the tool throws "cidr host bits must be zero".
- network, first_address and last_address are RFC 5952 canonical strings; network equals first_address.
- total_count is the canonical decimal string 2^(128-prefix), the number of addresses in the block. IPv6 has no broadcast address and this tool draws no usable/reserved distinction.

## Input

- `cidr` (string, required): max length 49

## Output

- `network` (string, required): max length 45
- `prefix` (integer, required): min 0; max 128
- `first_address` (string, required): max length 45
- `last_address` (string, required): max length 45
- `total_count` (string, required): max length 39; pattern `^(0|[1-9][0-9]*)$`

## Limits

- max cidr length: 49
- prefix min: 0
- prefix max: 128

## Example

Request input:

```json
{
  "cidr": "2001:db8::/32"
}
```

Response:

```json
{
  "result": {
    "network": "2001:db8::",
    "prefix": 32,
    "first_address": "2001:db8::",
    "last_address": "2001:db8:ffff:ffff:ffff:ffff:ffff:ffff",
    "total_count": "79228162514264337593543950336"
  }
}
```

## How to call it

### MCP

Connect `https://computefirst.net/mcp` ([setup](/docs#connect)), then call `execute` with:

```json
{
  "id": "ipv6-cidr-parse",
  "version": "1.0.0",
  "input": {
    "cidr": "2001:db8::/32"
  }
}
```

### HTTP (no key)

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

The machine-readable contract is at [/v1/tools/ipv6-cidr-parse/versions/1.0.0](/v1/tools/ipv6-cidr-parse/versions/1.0.0).

### CLI

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

Get the client at [/clients/cli/](/clients/cli/).

## Related tools

- [IPv4 CIDR parse](/tools/ipv4-cidr-parse): Parse an IPv4 CIDR block into its network, broadcast, netmask, wildcard mask, usable host range and address counts.
- [IPv6 CIDR contains](/tools/ipv6-cidr-contains): Test whether one IPv6 CIDR block fully contains another IPv6 CIDR block.
- [IPv6 CIDR overlap](/tools/ipv6-cidr-overlap): Test whether two IPv6 CIDR blocks overlap (share at least one address).
- [IPv6 in CIDR](/tools/ipv6-in-cidr): Test whether an IPv6 address lies in a CIDR prefix whose host bits are zero.
- [IPv6 parse](/tools/ipv6-parse): Parse an IPv6 address (any RFC 4291 textual form) into its 8 hextets and a 128-bit integer string.
- [IPv6 range to cidrs](/tools/ipv6-range-to-cidrs): Convert an arbitrary IPv6 address range into the minimal list of CIDR blocks that exactly covers it.