Creating custom bridge networks in Docker - Try It Yourself

Creating custom bridge networks

📖 Scenario: You are setting up Docker containers for a small app. To keep the containers organized and isolated, you want to create a custom bridge network. This helps containers communicate easily and keeps them separate from other Docker networks.

🎯 Goal: Create a custom Docker bridge network named my_custom_network. Then, run a container attached to this network and finally list all Docker networks to confirm your custom network is created.

📋 What You'll Learn

Create a Docker bridge network named my_custom_network

Run a Docker container named my_nginx using the nginx image attached to my_custom_network

List all Docker networks to verify my_custom_network exists

💡 Why This Matters

🌍 Real World

Custom Docker networks help isolate and organize containers in real projects, improving security and communication.

💼 Career

Understanding Docker networking is essential for DevOps roles managing containerized applications and infrastructure.

1

Create a custom Docker bridge network

Use the docker network create command to create a bridge network named my_custom_network.

Docker

# Create a Docker bridge network named my_custom_network
# Your code here

Hint

Use docker network create --driver bridge my_custom_network to create the network.

2

Run a container attached to the custom network

Run a Docker container named my_nginx using the nginx image. Attach it to the my_custom_network network using the --network option.

Docker

docker network create --driver bridge my_custom_network
# Run a container named my_nginx attached to my_custom_network
# Your code here

Hint

Use docker run -d --name my_nginx --network my_custom_network nginx to start the container.

3

List all Docker networks

Use the docker network ls command to list all Docker networks and confirm that my_custom_network is listed.

Docker

docker network create --driver bridge my_custom_network
docker run -d --name my_nginx --network my_custom_network nginx
# List all Docker networks
# Your code here

Hint

Simply run docker network ls to see all networks.

4

Display the custom network details

Use the docker network inspect command with my_custom_network to display detailed information about your custom network.

Docker

docker network create --driver bridge my_custom_network
docker run -d --name my_nginx --network my_custom_network nginx
docker network ls
# Inspect the my_custom_network details
# Your code here

Hint

Run docker network inspect my_custom_network to see the network details including connected containers.

Practice

1. What is the main purpose of creating a custom bridge network in Docker?

easy

A. To increase the CPU usage of containers

B. To allow containers to communicate privately and securely

C. To automatically update container images

D. To create a backup of container data

Solution

1. Step 1: Understand Docker networking basics

   Docker uses networks to connect containers. The default bridge network is shared and less secure.

2. Step 2: Purpose of custom bridge networks

   Custom bridge networks isolate containers, allowing private and secure communication between them.

3. Final Answer:

   To allow containers to communicate privately and securely -> Option B

4. Quick Check:

   Custom bridge network = private container communication [OK]

Hint: Custom bridge = private container communication [OK]

Common Mistakes:

• Thinking custom bridge increases CPU usage
• Confusing network creation with image updates
• Assuming it creates data backups

2. Which of the following is the correct command to create a custom bridge network named my_bridge?

easy

A. docker network create --driver bridge my_bridge

B. docker create network bridge my_bridge

C. docker network new --type bridge my_bridge

D. docker bridge create network my_bridge

Solution

1. Step 1: Recall Docker network creation syntax

   The correct syntax is docker network create --driver bridge NETWORK_NAME.

2. Step 2: Match the command with the syntax

   docker network create --driver bridge my_bridge matches the correct syntax exactly for creating a bridge network named my_bridge.

3. Final Answer:

   docker network create --driver bridge my_bridge -> Option A

4. Quick Check:

   Correct syntax = docker network create --driver bridge [OK]

Hint: Use 'docker network create --driver bridge NAME' [OK]

Common Mistakes:

• Using wrong command order
• Missing --driver flag
• Using 'new' or 'create' incorrectly

3. Given the command docker network create --driver bridge isolated_net, what will be the output of docker network ls related to this network?

medium

A. No change; the network list remains the same

B. An error message saying 'driver not found' will appear

C. The default bridge network will be removed

D. A new network named 'isolated_net' with driver 'bridge' will appear in the list

Solution

1. Step 1: Understand the effect of the create command

   The command creates a new bridge network named 'isolated_net'.

2. Step 2: Check the network list after creation

   Running docker network ls shows all networks including the newly created 'isolated_net' with driver 'bridge'.

3. Final Answer:

   A new network named 'isolated_net' with driver 'bridge' will appear in the list -> Option D

4. Quick Check:

   New bridge network appears in list [OK]

Hint: New bridge network shows in 'docker network ls' [OK]

Common Mistakes:

• Expecting an error for valid driver
• Thinking default bridge is removed
• Assuming no change in network list

4. You ran docker network create --driver bridge without specifying a network name. What is the likely result?

medium

A. Docker creates a network named 'bridge' by default

B. Docker creates a network with a random generated name

C. Docker throws an error about missing network name

D. Docker creates the default bridge network again

Solution

1. Step 1: Check required arguments for network creation

   The docker network create command requires a network name after options.

2. Step 2: Result of missing network name

   Omitting the network name causes Docker to throw an error indicating the missing argument.

3. Final Answer:

   Docker throws an error about missing network name -> Option C

4. Quick Check:

   Missing name causes error [OK]

Hint: Always specify network name after options [OK]

Common Mistakes:

• Assuming Docker auto-generates network name
• Thinking 'bridge' is default name created
• Confusing with default bridge network

5. You want two containers to communicate only with each other and not with other containers on the host. Which steps correctly create and use a custom bridge network named private_net?

hard

A. Create network with docker network create --driver bridge private_net and run containers with --network private_net

B. Run containers with --link option without creating a network

C. Use default bridge network and assign static IPs manually

D. Create network with docker network create private_net without specifying driver

Solution

1. Step 1: Create a custom bridge network

   Use docker network create --driver bridge private_net to create an isolated network.

2. Step 2: Run containers attached to this network

   Start containers with --network private_net so they communicate only within this network.

3. Final Answer:

   Create network with 'docker network create --driver bridge private_net' and run containers with '--network private_net' -> Option A

4. Quick Check:

   Custom bridge + --network = isolated container communication [OK]

Hint: Create bridge network then run containers with --network [OK]

Common Mistakes:

• Using --link which is deprecated
• Relying on default bridge for isolation
• Omitting --driver option causing default driver