Mastering Docker Network Basics

Introduction

This tutorial will cover the basics of using Docker networks. We will start with simple examples and move on to more complicated scenarios.

Skills Graph

%%%%{init: {'theme':'neutral'}}%%%% flowchart RL docker(("`Docker`")) -.-> docker/ContainerOperationsGroup(["`Container Operations`"]) docker(("`Docker`")) -.-> docker/NetworkOperationsGroup(["`Network Operations`"]) docker/ContainerOperationsGroup -.-> docker/exec("`Execute Command in Container`") docker/ContainerOperationsGroup -.-> docker/run("`Run a Container`") docker/NetworkOperationsGroup -.-> docker/network("`Manage Networks`") subgraph Lab Skills docker/exec -.-> lab-8445{{"`Mastering Docker Network Basics`"}} docker/run -.-> lab-8445{{"`Mastering Docker Network Basics`"}} docker/network -.-> lab-8445{{"`Mastering Docker Network Basics`"}} end

Create a Network

To create a network, we use the docker network create command. Let us create a bridge network named my-network:

docker network create my-network

We can verify that the network was created by running:

docker network ls

This will list all the available networks on your machine. You should see my-network listed.

NETWORK ID     NAME         DRIVER    SCOPE
1191cb61c989   bridge       bridge    local
91199fc6ad2e   host         host      local
32e2857073a9   minikube     bridge    local
47ac4e684a72   my-network   bridge    local
1078d2c781b6   none         null      local

Launch Containers in the Network

Now that we have a network, we can launch containers in it. Let us launch two containers and connect them to our my-network network:

docker run -d --name container1 --network my-network nginx
docker run -d --name container2 --network my-network nginx

The --network flag specifies the network that the container should be connected to.

View the output:

Unable to find image 'nginx:latest' locally
latest: Pulling from library/nginx
2f44b7a888fa: Pull complete
8b7dd3ed1dc3: Pull complete
35497dd96569: Pull complete
36664b6ce66b: Pull complete
2d455521f76c: Pull complete
dc9c4fdb83d6: Pull complete
8056d2bcf3b6: Pull complete
Digest: sha256:4c0fdaa8b6341bfdeca5f18f7837462c80cff90527ee35ef185571e1c327beac
Status: Downloaded newer image for nginx:latest
65a2412dcc717a0d1d46385dd57ca8a80faf517a0fb5b14ecf0defc5f4268f31
d05411b6115018d7d77b3f4e1b8ff381458af0481ce206acf4e503578d424619

Test Connectivity

We can now test connectivity between the containers. Let us execute a command in container1 that will access container2:

docker exec container1 curl container2

This should return the HTML content of the nginx web server running in container2.

labex:~/ $ docker exec container1 curl container2
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   615  100   615    0     0   376k      0 --:--:-- --:--:-- --:--:--  600k
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

Connect a Container to Multiple Networks

A container can be connected to multiple networks. Let us create another network and connect container2 to both networks:

docker network create my-network2
docker network connect my-network2 container2

We can verify that container2 is now connected to both networks by running:

docker network inspect my-network2

This will show the list of containers connected to the my-network2 network. You should see container2 listed.

Use the docker network inspect my-network2 | grep container2 call to get the direct result.

labex:~/ $ docker network inspect my-network2 | grep container2
                "Name": "container2",

Disconnect a Container from a Network

We can disconnect a container from a network using the docker network disconnect command. Let us disconnect container2 from my-network:

docker network disconnect my-network container2

We can verify that container2 is no longer connected to my-network by running:

docker network inspect my-network

This will show the list of containers connected to my-network. You should not see container2 listed.

Use the docker network inspect my-network | grep container call to get the direct result.

labex:~/ $ docker network inspect my-network | grep container
                "Name": "container1",

Remove a Network

We can remove a network using the docker network rm command. Let us remove "my-network2":

docker network disconnect my-network2 container2
docker network rm my-network2

We can verify that "my-network2" was removed by running:

docker network ls

This will list all the available networks on your machine. You should not see "my-network2" listed.

NETWORK ID     NAME         DRIVER    SCOPE
1191cb61c989   bridge       bridge    local
91199fc6ad2e   host         host      local
32e2857073a9   minikube     bridge    local
47ac4e684a72   my-network   bridge    local
1078d2c781b6   none         null      local

Summary

In this tutorial, we covered the basics of using Docker networks. We created a network, launched containers in the network, tested connectivity, connected a container to multiple networks, disconnected a container from a network, and removed a network.