Network drivers (bridge, host, overlay, none) in Docker - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the bridge network driver in Docker?

The bridge driver creates a private internal network on the host. Containers on this network can communicate with each other but are isolated from the host network unless ports are published.

beginner

How does the host network driver work in Docker?

The host driver makes the container use the host's network stack directly. This means the container shares the host's IP address and ports, with no network isolation.

intermediate

What is the purpose of the overlay network driver in Docker?

The overlay driver connects multiple Docker daemons together to create a distributed network. It allows containers on different hosts to communicate securely as if on the same network.

beginner

What does the none network driver do in Docker?

The none driver disables all networking for the container. The container has no network interfaces except a loopback interface, isolating it completely from any network.

intermediate

When would you use the host network driver instead of bridge?

Use host networking when you want the container to have full access to the host network for performance or compatibility reasons, like running network monitoring tools.

Which Docker network driver isolates containers with their own private network on the host?

A bridge

B host

C overlay

D none

The bridge driver creates a private network for containers on the host, isolating them from the host network.

Which network driver allows containers to share the host's network stack directly?

A overlay

B none

C host

D bridge

The host driver makes containers use the host's network stack, sharing IP and ports.

What is the main use case for the overlay network driver?

A Isolating containers with no network

B Connecting containers across multiple hosts

C Sharing host network stack

D Creating a private network on one host

Overlay networks connect containers on different Docker hosts to communicate securely.

If you want a container with no network access, which driver should you choose?

A none

B host

C overlay

D bridge

The none driver disables all networking for the container.

Which network driver would you use for better network performance by avoiding network isolation?

A none

B bridge

C overlay

D host

Host networking avoids network isolation, giving better performance by sharing the host's network stack.

Explain the differences between the Docker network drivers: bridge, host, overlay, and none.

Think about how each driver handles container network isolation and communication.

When would you choose the overlay network driver over the bridge driver in Docker?

Consider multi-host container communication scenarios.

Practice

1. Which Docker network driver allows containers on the same host to communicate using a private internal network?

easy

A. bridge

B. host

C. overlay

D. none

Solution

1. Step 1: Understand the purpose of the bridge driver

   The bridge driver creates a private network internal to the host, allowing containers to communicate securely on the same machine.

2. Step 2: Compare with other drivers

   The host driver uses the host's network directly, overlay connects containers across hosts, and none disables networking.

3. Final Answer:

   bridge -> Option A

4. Quick Check:

   Private internal network = bridge [OK]

Hint: Bridge = private network on one host [OK]

Common Mistakes:

• Confusing host with bridge driver
• Thinking overlay works on single host only
• Assuming none allows communication

2. Which command correctly creates a Docker container using the host network driver?

easy

A. docker run --network=bridge nginx

B. docker run --net=overlay nginx

C. docker run --network=host nginx

D. docker run --network=none nginx

Solution

1. Step 1: Identify the correct syntax for network option

   The correct flag is --network= followed by the driver name, e.g., host.

2. Step 2: Match the driver to the command

   docker run --network=host nginx uses --network=host which is the correct way to assign the host network driver.

3. Final Answer:

   docker run --network=host nginx -> Option C

4. Quick Check:

   Use --network=host for host driver [OK]

Hint: Use --network=host to assign host driver [OK]

Common Mistakes:

• Using --net=overlay instead of --network=overlay
• Confusing bridge and host flags
• Omitting the network flag

3. Given two Docker hosts connected with an overlay network named mynet, what will happen if you run docker network inspect mynet on one host?

medium

A. It shows no containers because overlay networks isolate containers

B. It shows only local bridge network details

C. It returns an error because overlay networks can't be inspected

D. It shows details of the overlay network including connected containers across hosts

Solution

1. Step 1: Understand overlay network scope

   Overlay networks span multiple Docker hosts, connecting containers across them.

2. Step 2: Inspect command behavior

   docker network inspect shows detailed info about the network, including containers connected on all hosts.

3. Final Answer:

   It shows details of the overlay network including connected containers across hosts -> Option D

4. Quick Check:

   Overlay network inspect shows multi-host details [OK]

Hint: Overlay networks span hosts; inspect shows all connected containers [OK]

Common Mistakes:

• Thinking overlay networks can't be inspected
• Assuming inspect shows only local containers
• Confusing overlay with none driver

4. You created a container with --network=none but it still can ping the host. What is the likely cause?

medium

A. The container has another network interface configured manually

B. The none driver allows all network traffic by default

C. Docker daemon is ignoring the network flag

D. The container is running in host network mode

Solution

1. Step 1: Understand the none network driver

   The none driver disables Docker-managed networking, so no automatic network interfaces are created.

2. Step 2: Analyze why container can ping host

   If the container can ping the host, it likely has a manually configured network interface inside the container.

3. Final Answer:

   The container has another network interface configured manually -> Option A

4. Quick Check:

   none disables Docker network; manual config allows connectivity [OK]

Hint: none disables Docker network; manual setup can override [OK]

Common Mistakes:

• Assuming none allows all traffic
• Thinking Docker ignores network flags
• Confusing none with host driver

5. You want to deploy a multi-host Docker Swarm service where containers communicate securely across hosts. Which network driver should you use and why?

hard

A. bridge, because it isolates containers on each host

B. overlay, because it connects containers across multiple hosts securely

C. host, because it uses the host network for better performance

D. none, because it disables networking for security

Solution

1. Step 1: Identify network needs for multi-host communication

   Containers on different hosts need a network driver that spans hosts and provides secure communication.

2. Step 2: Match drivers to requirements

   Bridge works only on one host, host shares host network (not multi-host), none disables networking, overlay connects containers across hosts securely.

3. Final Answer:

   overlay, because it connects containers across multiple hosts securely -> Option B

4. Quick Check:

   Multi-host secure communication = overlay [OK]

Hint: Overlay = multi-host secure network [OK]

Common Mistakes:

• Choosing bridge for multi-host
• Using host driver for container isolation
• Thinking none enables communication