Creating custom bridge networks in Docker - Quick Revision & Summary

Recall & Review

beginner

What is a custom bridge network in Docker?

A custom bridge network is a user-defined network that allows Docker containers to communicate with each other on the same host with isolated network settings.

beginner

Which Docker command creates a custom bridge network named 'my_bridge'?

docker network create --driver bridge my_bridge

intermediate

Why use a custom bridge network instead of the default bridge network?

Custom bridge networks provide better isolation, allow container name resolution, and enable easier management of container communication.

beginner

How do containers communicate on a custom bridge network?

Containers on the same custom bridge network can communicate using container names as hostnames, simplifying service discovery.

intermediate

What happens if you try to connect a container to a non-existent custom bridge network?

Docker will return an error saying the network does not exist, and the container will not start or connect until the network is created.

Which command creates a custom bridge network in Docker?

A docker create network bridge my_network

B docker network create --driver bridge my_network

C docker network new bridge my_network

D docker bridge create my_network

The correct syntax to create a custom bridge network is 'docker network create --driver bridge '.

What is the default driver used when creating a custom bridge network?

A none

B overlay

C host

D bridge

The 'bridge' driver is the default for custom bridge networks in Docker.

How can containers on a custom bridge network communicate with each other?

A Only through published ports

B Using container IP addresses only

C Using container names as hostnames

D They cannot communicate

Containers on the same custom bridge network can use container names as hostnames to communicate.

What command lists all Docker networks including custom bridge networks?

A docker network ls

B docker network show

C docker network list all

D docker networks

'docker network ls' lists all Docker networks on the host.

What happens if you remove a custom bridge network while containers are connected to it?

A Containers lose network connectivity and may stop

B Docker automatically reconnects containers to default network

C Nothing happens

D Containers keep running and stay connected

Removing a custom bridge network disconnects containers, causing network loss and possible container failure.

Explain how to create and use a custom bridge network in Docker.

Think about the command to create the network and how containers talk to each other on it.

Describe the benefits of using a custom bridge network over the default Docker bridge network.

Consider what problems the default network might have that a custom one solves.

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