---
title: Networks top-level elements
description: Explore all the attributes the networks top-level element can have.
keywords: compose, compose specification, networks, compose file reference
aliases:
 - /compose/compose-file/06-networks/
weight: 30
---

{{% include "compose/networks.md" %}}

To use a network across multiple services, you must explicitly grant each service access by using the [networks](services.md) attribute within the `services` top-level element. The `networks` top-level element has additional syntax that provides more granular control.

## Examples

### Basic example

In the following example, at runtime, networks `front-tier` and `back-tier` are created and the `frontend` service
is connected to `front-tier` and `back-tier` networks.

```yml
services:
  frontend:
    image: example/webapp
    networks:
      - front-tier
      - back-tier

networks:
  front-tier:
  back-tier:
```

### Advanced example

```yml
services:
  proxy:
    build: ./proxy
    networks:
      - frontend
  app:
    build: ./app
    networks:
      - frontend
      - backend
  db:
    image: postgres
    networks:
      - backend

networks:
  frontend:
    # Specify driver options
    driver: bridge
    driver_opts:
      com.docker.network.bridge.host_binding_ipv4: "127.0.0.1"
  backend:
    # Use a custom driver
    driver: custom-driver
```

The advanced example shows a Compose file which defines two custom networks. The `proxy` service is isolated from the `db` service, because they do not share a network in common. Only `app` can talk to both.

## The default network

When a Compose file doesn't declare explicit networks, Compose uses an implicit `default` network. Services without an explicit [`networks`](services.md#networks) declaration are connected by Compose to this `default` network:


```yml
services:
  some-service:
    image: foo
```
This example is actually equivalent to:

```yml
services:
  some-service:
    image: foo
    networks:
      default: {}  
networks:
  default: {}      
```

You can customize the `default` network with an explicit declaration:

```yml
networks:
  default: 
    name: a_network # Use a custom name
    driver_opts:    # pass options to driver for network creation
      com.docker.network.bridge.host_binding_ipv4: 127.0.0.1
```

For options, see the [Docker Engine docs](https://docs.docker.com/engine/network/drivers/bridge/#options).

## Attributes

### `driver`

`driver` specifies which driver should be used for this network. Compose returns an error if the
driver is not available on the platform.

```yml
networks:
  db-data:
    driver: bridge
```

For more information on drivers and available options, see [Network drivers](/manuals/engine/network/drivers/_index.md).

### `driver_opts`

`driver_opts` specifies a list of options as key-value pairs to pass to the driver. These options are
driver-dependent.

```yml
networks:
  frontend:
    driver: bridge
    driver_opts:
      com.docker.network.bridge.host_binding_ipv4: "127.0.0.1"
```

Consult the [network drivers documentation](/manuals/engine/network/_index.md) for more information.

### `attachable`

If `attachable` is set to `true`, then standalone containers should be able to attach to this network, in addition to services.
If a standalone container attaches to the network, it can communicate with services and other standalone containers
that are also attached to the network.

```yml
networks:
  mynet1:
    driver: overlay
    attachable: true
```

### `enable_ipv4`

{{< summary-bar feature_name="Compose enable ipv4" >}}

`enable_ipv4` can be used to disable IPv4 address assignment.