What is the default Docker network mode?

The default Docker network mode is Bridge mode. This mode is designed to create a private internal network on your machine, allowing containers to communicate with each other while also isolating their networking. When Docker is installed and a container is created without specifying a network mode, it automatically connects to this bridge network.

Bridge mode provides a way for containers to obtain IP addresses and be reachable from other containers on the same host, enabling inter-container communication. It also allows for network address translation (NAT), which helps in accessing containers from the host or external network resources.

In contrast, Host mode binds the container's network stack to the host, meaning the container shares the host’s IP address, which can create issues with networking separation between containers. Overlay mode is used in Docker Swarm for multi-host networking but is not the default for standalone containers. None mode essentially disables all networking for the container, which is not practical for most use cases.