In this scenario you'll learn how to use Overlay Networks as part of Swarm Mode. Overlay networks allow containers to communicate as if they're on the same host. Under the covers they use VxLan features of the Linux Kernel.
The environment has been configured with two Docker machines that can communicate with each over TCP.
Create Overlay Network
Step 1 - Initialise Swarm Mode
By default, Docker works as an isolated single-node. All containers are only deployed onto the engine. Swarm Mode turns it into a multi-host cluster-aware engine.
Task: Initialise Swarm Mode
To use the secrets functionality, Docker has to be in "Swarm Mode". This is enabled via
docker swarm init
Join Swarm Mode
Execute the command below on the second host to add it as a worker to the cluster.
token=$(ssh -o StrictHostKeyChecking=no [[HOST_IP]] "docker swarm join-token -q worker") && docker swarm join [[HOST_IP]]:2377 --token $token