---
description: Learn how to build your own bridge interface
keywords: docker, bridge, docker0, network
title: Build your own bridge
---

This section explains how to build your own bridge to replace the Docker default
bridge. This is a `bridge` network named `bridge` created automatically when you
install Docker.

> **Note**: The [Docker networks feature](../index.md) allows you to
create user-defined networks in addition to the default bridge network.

You can set up your own bridge before starting Docker and configure Docker to
use your bridge instead of the default `docker0` bridge.

> **Note**: These instructions use the `ip` command, which is available on
> all modern Linux distributions. If you do not have the `ip` command, you may
> need to use the `brctl` command. Instructions for that command are out of
> scope for this topic.

1.  Create the new bridge, configure it to use the IP address pool
    `192.168.5.0 - 192.168.5.255`, and activate it.

    ```bash
    $ sudo ip link add name bridge0 type bridge
    $ sudo ip addr add 192.168.5.1/24 dev bridge0
    $ sudo ip link set dev bridge0 up
    ```

    Display the new bridge's settings.

    ```bash
    $ ip addr show bridge0

    4: bridge0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state UP group default
        link/ether 66:38:d0:0d:76:18 brd ff:ff:ff:ff:ff:ff
        inet 192.168.5.1/24 scope global bridge0
           valid_lft forever preferred_lft forever
    ```

2.  Configure Docker to use the new bridge by setting the option in the
    `daemon.json` file, which is located in `/etc/docker/` on
    Linux or `C:\ProgramData\docker\config\` on Windows Server. On Docker for
    Mac or Docker for Windows, click the Docker icon, choose **Preferences**,
    and go to **Daemon**.

    If the `daemon.json` file does not exist, create it. Assuming there
    are no other settings in the file, it should have the following contents:

    ```json
    {
      "bridge": "bridge0"
    }
    ```

    Restart Docker for the changes to take effect.

3.  Confirm that the new outgoing NAT masquerade is set up.

    ```bash
    $ sudo iptables -t nat -L -n

    Chain POSTROUTING (policy ACCEPT)
    target     prot opt source               destination
    MASQUERADE  all  --  192.168.5.0/24      0.0.0.0/0
    ```

4.  Remove the now-unused `docker0` bridge and flush the `POSTROUTING` table.

    ```bash
    $ sudo ip link set dev docker0 down

    $ sudo ip link del name br0

    $ sudo iptables -t nat -F POSTROUTING
    ```

5.  Create a new container, and verify that it uses an IP the new IP address range.

When you add and remove interfaces from the bridge by starting and stopping
containers, you can run `ip addr` and `ip route` inside a container to confirm
that it has an address in the bridge's IP address range and uses the Docker
host's IP address on the bridge as its default gateway to the rest of the
Internet.