Creating custom bridge networks in Docker - Step-by-Step CLI Walkthrough

Introduction

Sometimes, you want your Docker containers to talk to each other in a private space without interference. Creating a custom bridge network lets you control how containers connect and communicate securely on your machine.

When you want to isolate a group of containers from others on your system for security.

When you need containers to communicate using custom network settings like specific IP ranges.

When you want to give containers easy-to-remember names to connect instead of IP addresses.

When you want to avoid conflicts with Docker's default network settings.

When you want to connect containers across multiple Docker hosts using the same network name.

Commands

This command creates a new custom bridge network named 'my-custom-network' so containers can connect to it and communicate privately.

Terminal

docker network create --driver bridge my-custom-network

Expected Output

3d2e1f4a5b6c7d8e9f0a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3

→

--driver bridge - Specifies the network type as a bridge network.

Lists all Docker networks so you can verify that 'my-custom-network' was created successfully.

Terminal

docker network ls

Expected Output

NETWORK ID     NAME                DRIVER    SCOPE

3d2e1f4a5b6c   bridge              bridge    local

7f8g9h0i1j2k   host                host      local

9l0m1n2o3p4q   none                null      local

3d2e1f4a5b6c   my-custom-network   bridge    local

Runs a new container named 'my-app' using the nginx image and connects it to the custom bridge network so it can communicate with other containers on this network.

Terminal

docker run -d --name my-app --network my-custom-network nginx

Expected Output

a1b2c3d4e5f67890123456789abcdef0123456789abcdef0123456789abcdef0

→

--network my-custom-network - Connects the container to the custom bridge network.

→

-d - Runs the container in detached mode (in the background).

Shows detailed information about the custom bridge network, including connected containers and IP address ranges.

Terminal

docker network inspect my-custom-network

Expected Output

[

    {

        "Name": "my-custom-network",

        "Id": "3d2e1f4a5b6c7d8e9f0a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3",

        "Created": "2024-06-01T12:00:00.000000000Z",

        "Scope": "local",

        "Driver": "bridge",

        "EnableIPv6": false,

        "IPAM": {

            "Driver": "default",

            "Options": null,

            "Config": [

                {

                    "Subnet": "172.18.0.0/16",

                    "Gateway": "172.18.0.1"

                }

            ]

        },

        "Containers": {

            "a1b2c3d4e5f67890123456789abcdef0123456789abcdef0123456789abcdef0": {

                "Name": "my-app",

                "EndpointID": "e1f2a3b4c5d6e7f8a9b0c1d2e3f4g5h6i7j8k9l0m1n2o3p4q5r6s7t8u9v0w1x2",

                "MacAddress": "02:42:ac:12:00:02",

                "IPv4Address": "172.18.0.2/16",

                "IPv6Address": ""

            }

        },

        "Options": {},

        "Labels": {}

    }

]

Key Concept

If you remember nothing else from this pattern, remember: custom bridge networks let your containers talk privately and safely with custom settings.

Common Mistakes

Not specifying the --driver bridge flag when creating the network.

Docker might create a network with a different driver, causing unexpected behavior or incompatibility.

Always include --driver bridge to ensure the network is a bridge type.

Forgetting to connect containers to the custom network using --network flag.

Containers will connect to the default network and won't communicate on the custom network.

Use --network my-custom-network when running containers to connect them properly.

Assuming the network is created without checking with docker network ls.

The network might fail to create due to name conflicts or other errors, causing confusion later.

Always verify network creation with docker network ls before running containers.

Summary

Create a custom bridge network with docker network create --driver bridge my-custom-network.

Verify the network exists using docker network ls.

Run containers connected to this network using docker run --network my-custom-network.

Inspect the network details and connected containers with docker network inspect my-custom-network.