4.2 Lab - Docker Networking

Introduction

In this hands-on lab, you will explore Docker networking fundamentals by performing tasks that involve creating and managing Docker networks. You will use the Nano editor in a Linux environment to edit configuration files and Docker commands to manipulate Docker networks and container connections. This lab provides a practical introduction to Docker's networking capabilities, allowing you to understand how containers can communicate within the same host and across different networks.

Objectives

• Understand how to create and manage Docker networks.
• Learn to connect and disconnect containers from networks.
• Explore the communication between containers on the same network.
• Use the Nano editor to edit configuration files in a Linux environment.

Lab Steps

Step 1: Preparing Your Environment

• Ensure Docker is installed on your Linux environment.
• Install Nano if it is not already installed by using sudo apt-get install nano or the appropriate package manager command for your Linux distribution.

Step 2: Creating a Custom Bridge Network

• Open a terminal.
• Create a new bridge network named my-bridge-net:

  docker network create --driver bridge my-bridge-net
  

• Verify the network creation by listing all Docker networks:

  docker network ls
  

Step 3: Running Containers and Connecting to the Network

• Run two Alpine containers and connect them to my-bridge-net. These containers will remain idle and open for interactive commands:

  docker run -dit --name alpine1 --network my-bridge-net alpine ash
  docker run -dit --name alpine2 --network my-bridge-net alpine ash
  

Step 4: Inspecting Network Configuration

• Inspect my-bridge-net to view the connected containers and network details:

  docker network inspect my-bridge-net
  

Step 5: Communication Between Containers

• Use docker exec to ping alpine2 from alpine1 using its container name, demonstrating inter-container communication within the same network:

  docker exec alpine1 ping -c 4 alpine2
  

• Observe successful ping attempts indicating network communication.

Step 6: Editing Configuration with Nano

• For demonstration purposes, let's create a simple script to ping a container. First, use Nano to create a bash script inside alpine1:

  docker exec -it alpine1 vi /ping_script.sh
  

• Type the following script, then save and exit vi (ESC, :x):

  #!/bin/sh
  ping -c 4 alpine2
  

• Make the script executable and run it:

  docker exec alpine1 chmod +x /ping_script.sh
  docker exec alpine1 /ping_script.sh
  

You should see the following output:

PING alpine2 (172.18.0.3): 56 data bytes
64 bytes from 172.18.0.3: seq=0 ttl=64 time=0.071 ms
64 bytes from 172.18.0.3: seq=1 ttl=64 time=0.090 ms
64 bytes from 172.18.0.3: seq=2 ttl=64 time=0.091 ms
64 bytes from 172.18.0.3: seq=3 ttl=64 time=0.090 ms

--- alpine2 ping statistics ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 0.071/0.085/0.091 ms

Summary

In this lab, you've gained hands-on experience with Docker networking by creating a custom bridge network and connecting containers to it. You explored how containers can communicate with each other on the same network and used the Nano editor to edit a simple script within a container. This lab has demonstrated the power and flexibility of Docker networking, providing a foundation for more complex networking scenarios and configurations. Understanding Docker networking is essential for building and managing containerized applications effectively.