Creating custom bridge networks in Docker - Practice Exercises

Challenge - 5 Problems

💻 Command Output

intermediate

Output of creating a custom bridge network

What is the output when you run the command to create a custom bridge network named my_bridge?

Docker

docker network create --driver bridge my_bridge

A a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6q7r8s9t0u1v2w3x4y5z6

B Error: network driver not found

C Network my_bridge already exists

D 1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef

💡 Hint

The command returns a network ID which is a long hexadecimal string.

When you create a custom bridge network, Docker returns the network ID, which is a 64-character hexadecimal string. The output confirms successful creation.

🧠 Conceptual

intermediate

Purpose of custom bridge networks

Why would you create a custom bridge network instead of using the default bridge network in Docker?

A To isolate containers and control communication between them

B To increase container CPU usage automatically

C To disable container networking completely

D To allow containers to use host network interfaces directly

💡 Hint

Think about network isolation and container communication control.

Custom bridge networks allow you to isolate containers and control how they communicate, unlike the default bridge network which is shared by all containers.

❓ Configuration

advanced

Correct Docker network create command with subnet

Which command correctly creates a custom bridge network named custom_net with subnet 192.168.100.0/24?

A docker network create --driver bridge --subnet=192.168.100.0/24 custom_net

B docker network create --subnet 192.168.100.0/24 --driver=bridge custom_net

C docker network create custom_net --driver bridge --subnet 192.168.100.0/24

D docker network create --driver=bridge custom_net --subnet=192.168.100.0/24

💡 Hint

The subnet option uses an equals sign and comes after the driver option.

The correct syntax requires the --subnet option with an equals sign and the network name last. Option A follows the correct order and syntax.

❓ Troubleshoot

advanced

Troubleshooting network creation failure

You run docker network create --driver bridge --subnet=192.168.1.0/24 mynet but get the error: Error response from daemon: Pool overlaps with other one on this address space. What is the most likely cause?

A The network name mynet is invalid

B The subnet 192.168.1.0/24 is already used by another Docker network

C The bridge driver is not installed

D The Docker daemon is not running

💡 Hint

The error mentions overlapping address space.

Docker prevents creating networks with overlapping subnets to avoid IP conflicts. The error means the subnet is already in use by another network.

🔀 Workflow

expert

Order of commands to create and use a custom bridge network

Put these steps in the correct order to create a custom bridge network and run a container attached to it:

A 2,4,3,1

B 3,2,4,1

C 2,3,4,1

D 1,2,3,4

💡 Hint

You must create the network before running containers on it.

First create the network (2), then list networks to confirm (3), inspect details (4), and finally run the container attached to it (1).