- `external` specifies that this network’s lifecycle is maintained outside of that of the application.
Compose doesn't attempt to create these networks, and returns an error if one doesn't exist.
 - All other attributes apart from name are irrelevant. If Compose detects any other attribute, it rejects the Compose file as invalid.

In the following example, `proxy` is the gateway to the outside world. Instead of attempting to create a network, Compose
queries the platform for an existing network simply called `outside` and connects the
`proxy` service's containers to it.

```yml
services:
  proxy:
    image: example/proxy
    networks:
      - outside
      - default
  app:
    image: example/app
    networks:
      - default

networks:
  outside:
    external: true
```

### `ipam`

`ipam` specifies a custom IPAM configuration. This is an object with several properties, each of which is optional:

- `driver`: Custom IPAM driver, instead of the default.
- `config`: A list with zero or more configuration elements, each containing a:
  - `subnet`: Subnet in CIDR format that represents a network segment
  - `ip_range`: Range of IPs from which to allocate container IPs
  - `gateway`: IPv4 or IPv6 gateway for the master subnet
  - `aux_addresses`: Auxiliary IPv4 or IPv6 addresses used by Network driver, as a mapping from hostname to IP
- `options`: Driver-specific options as a key-value mapping.

```yml
networks:
  mynet1:
    ipam:
      driver: default
      config:
        - subnet: 172.28.0.0/16
          ip_range: 172.28.5.0/24
          gateway: 172.28.5.254
          aux_addresses:
            host1: 172.28.1.5
            host2: 172.28.1.6
            host3: 172.28.1.7
      options:
        foo: bar
        baz: "0"
```

### `internal`

By default, Compose provides external connectivity to networks. `internal`, when set to `true`, lets you
create an externally isolated network.

### `labels`

Add metadata to containers using `labels`. You can use either an array or a dictionary.

It is recommended that you use reverse-DNS notation to prevent labels from conflicting with those used by other software.

```yml
networks:
  mynet1:
    labels:
      com.example.description: "Financial transaction network"
      com.example.department: "Finance"
      com.example.label-with-empty-value: ""
```

```yml
networks:
  mynet1:
    labels:
      - "com.example.description=Financial transaction network"
      - "com.example.department=Finance"
      - "com.example.label-with-empty-value"
```

Compose sets `com.docker.compose.project` and `com.docker.compose.network` labels.

### `name`

`name` sets a custom name for the network. The name field can be used to reference networks which contain special characters.
The name is used as is and is not scoped with the project name.

```yml
networks:
  network1:
    name: my-app-net
```

It can also be used in conjunction with the `external` property to define the platform network that Compose
should retrieve, typically by using a parameter so the Compose file doesn't need to hard-code runtime specific values:

```yml
networks:
  network1:
    external: true
    name: "${NETWORK_ID}"
```

## Additional resources

For more examples, see [Networking in Compose](/manuals/compose/how-tos/networking.md).