What is the default network mode for Docker containers?

The default network mode for Docker containers is Bridge mode. In this mode, Docker creates a private internal network on your host system, and each container is connected to this bridge network by default. This allows containers to communicate with each other using their IP addresses, while also being able to communicate with the external world through network address translation (NAT).

When containers are run in Bridge mode, Docker automatically assigns them unique IP addresses from a private address space, enabling inter-container communication. This mode is particularly useful for applications that need to be isolated from each other but still require network connectivity. The Bridge mode also simplifies network configurations, as users do not have to manually set up networking for individual containers.

While other modes like Host and Overlay serve specific use cases, they are not the default. Host mode allows containers to share the host’s network stack, which can lead to port conflicts and increased complexity in certain environments. Overlay mode is designed for multi-host networking, making it suitable for orchestrators like Docker Swarm or Kubernetes but is not applicable by default for single-host setups. Understanding the default Bridge mode is crucial for mastering Docker's networking options during operations and deployments.