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Custom Network

We can create custom bridge networks so that containers can communicate with each other if we want them to, but still otherwise remain isolated. Let's build a system where our application servers are hidden within a custom network, and only our load balancer is exposed to the host.

This is a very common setup in backend architecture. The load balancer is exposed to the public internet, but the application servers are only accessible via the load balancer.

Assignment

Let's create a custom bridge network called "caddytest".

docker network create caddytest

See if it worked by listing all the networks:

docker network ls

Stop the containers and spin up new ones with the same docker run command from the previous lesson, but this time, make sure you attach them to the caddytest network.
- Use the --network caddytest flag to attach them to the network
- Use the --name flag to name them caddy1 and caddy2 respectively so it's easier to reference them later
- Place these flags before the image name (caddy) in your docker run command. For example:
```
   docker run -d --name caddy1 --network caddytest -v $PWD/index1.html:/usr/share/caddy/index.html caddy
```
- Do not use the -p flag to expose ports. We don't want these accessible from the host machine.
Create another "getting started" container on the same network and start a shell session within it:

docker run -it --network caddytest docker/getting-started /bin/sh

By giving our containers some names, caddy1 and caddy2, and providing a bridge network, Docker has set up name resolution for us! The container names resolve to the individual containers from all other containers on the network.

Within your docker/getting-started container shell, curl the first container:

curl caddy1

Also curl the second container:

curl caddy2

If you get the HTML responses that you expect, exit out of your shell session within the "getting started" container.

Run and submit the CLI tests.

If you need to restart your caddy application servers after naming them, you can use: docker start caddy1 and docker start caddy2.