Which network driver connects containers directly to a network stack on the host machine without any isolation?

The host network driver connects containers directly to the network stack of the host machine, allowing containers to share the same IP address and port space as the host. This means that there is no network isolation between the containers and the host, which can be beneficial for performance since it eliminates the overhead of virtual networking.

When using the host driver, any networking configuration that applies to the host machine will also apply to the containers. This is particularly useful for high-performance applications or scenarios where the application inside the container needs to be as close to the host's networking capabilities as possible. However, this connection to the host's network stack means that any security or isolation that would typically be present in Docker's default bridge network is absent, so it should be used with caution.

In contrast, other network drivers like bridge and overlay provide varying degrees of isolation and are typically used for different networking contexts in Docker environments. The macvlan driver allows containers to have a dedicated MAC address and appear as physical devices on the network, enhancing isolation and network management for certain types of deployments, but does not operate in the same manner as the host driver.