# IPv4 CIDR contains

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

Test whether one IPv4 CIDR block fully contains another IPv4 CIDR block.

**Use when you need to: ipv4 cidr contains · ipv4 subnet contains subnet · check ipv4 cidr containment.**

## Supported

- ipv4 cidr contains
- ipv4 subnet contains subnet
- check ipv4 cidr containment

## Not supported

- IPv6
- partial/overlap-only containment

## Behavior

- outer and inner are each dotted-decimal/prefix with host bits zero; otherwise the tool throws.
- contains is true iff every address in inner also lies in outer, i.e. inner.prefix >= outer.prefix and inner's range is a subset of outer's range.
- A CIDR always contains itself (equal blocks yield contains: true).

## Input

- `outer` (string, required): max length 18
- `inner` (string, required): max length 18

## Output

- `contains` (boolean, required)
- `outer_network` (string, required): max length 18
- `inner_network` (string, required): max length 18

## Limits

- max cidr length: 18

## Example

Request input:

```json
{
  "outer": "10.0.0.0/8",
  "inner": "10.1.0.0/16"
}
```

Response:

```json
{
  "result": {
    "contains": true,
    "outer_network": "10.0.0.0/8",
    "inner_network": "10.1.0.0/16"
  }
}
```

## How to call it

### MCP

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

```json
{
  "id": "ipv4-cidr-contains",
  "version": "1.0.0",
  "input": {
    "outer": "10.0.0.0/8",
    "inner": "10.1.0.0/16"
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/ipv4-cidr-contains/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"outer":"10.0.0.0/8","inner":"10.1.0.0/16"}'
```

The machine-readable contract is at [/v1/tools/ipv4-cidr-contains/versions/1.0.0](/v1/tools/ipv4-cidr-contains/versions/1.0.0).

### CLI

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

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

## Related tools

- [IPv6 CIDR contains](/tools/ipv6-cidr-contains): Test whether one IPv6 CIDR block fully contains another IPv6 CIDR block.
- [IPv4 CIDR overlap](/tools/ipv4-cidr-overlap): Test whether two IPv4 CIDR blocks overlap (share at least one address).
- [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.
- [IPv4 in CIDR](/tools/ipv4-in-cidr): Test whether a canonical IPv4 address lies in a CIDR prefix whose host bits are zero.
- [IPv6 CIDR overlap](/tools/ipv6-cidr-overlap): Test whether two IPv6 CIDR blocks overlap (share at least one address).
- [IPv4 CIDR aggregate](/tools/ipv4-cidr-aggregate): Merge a list of IPv4 CIDR blocks into the minimal equivalent list of non-overlapping CIDR blocks.