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Docker Networking - Understanding Default, Custom, and Host Networks

There are 3 main docker networks are often used in docker: default-bridge, custom-bridge and host as shown below.

eric:~/ $ sudo docker network ls
NETWORK ID     NAME                                    DRIVER    SCOPE
d24be9f53feb   eric-custom_default                     bridge    local
c30973bff868   bridge                                  bridge    local
3a59a9c37489   host                                    host      local
33c951c94419   none                                    null      local

When running ip address show command, you will be seeing all networks including docker0 and br-<network_id>.

ac2acb09bd2719e5a925b1fb08e1ab52.png

1. Default Bridge Network (Name: bridge)​

When using docker run without specifying a network, Docker assigns the container to the default bridge network.

default-bridge.png

🔗 Source: NetworkChuck on YouTube

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⚠️ This default network does not support container name resolution, meaning containers cannot communicate using service names. It is generally not recommended for production use.

2. Custom Bridge Network (e.g., eric-custom)​

Custom bridge networks behave similarly to the default bridge but support DNS-based container name resolution. This allows containers to talk to each other using their service names, which is essential for many applications.

custom-bridge.png

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💡 When using docker-compose up or docker compose up, Docker automatically creates a custom bridge network named <project_name>_default. The project_name defaults to the name of the directory containing the docker-compose.yml file.

3. Host Network (Name: host)​

The host network mode allows containers to share the host's network stack. The container will not get its own IP but instead use the host's IP address and port space.

host-network.png

This offers better performance (due to no NAT layer) but increases the risk of security vulnerabilities, as the container can directly access the host's network interfaces and services.

🌐 Use Case: Cloudflare Tunnel with Host Network​

Use case: Cloudflare Tunnel
A practical example of using the host network is running a Cloudflare Tunnel container. By sharing the host’s network stack, the container behaves like a native background process. This makes it easier to expose services running on the host machine to the internet via Cloudflare's secure tunneling service.

🔧 Extra Tips: Advanced Networking with Docker​

🛠 How to Create a Custom Network​

You can manually create a custom network using:

docker network create my-custom-network

You can also add options like --subnet and --gateway for custom IP settings.

🔗 Sharing a Network Across Multiple Docker Compose Projects​

  1. First, create a shared external network:
docker network create shared-net
  1. In each docker-compose.yml, specify the external network:
networks:
  default:
    external:
      name: shared-net

This allows containers from different Compose projects to communicate with each other.

🔍 Inspecting Docker Networks​

You can inspect a network’s details using:

docker network inspect <network_name>

This provides useful information such as connected containers, subnet, gateway, etc.—handy for debugging.