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Docker Series: Episode 22 — Docker Networking Advanced: Multi-Host & Overlay Networks 🌐


This content originally appeared on DEV Community and was authored by Yash Sonawane

Welcome back! After covering basic networking, Docker Compose, Swarm, and logging, it’s time to tackle advanced Docker networking for multi-host setups. This is essential when deploying scalable applications across multiple machines.

🔹 Why Advanced Networking?

  • Containers need to communicate across different hosts.
  • Overlay networks allow seamless communication between containers on different machines.
  • Useful for Swarm clusters or distributed applications.

🔹 Overlay Network

  • Overlay networks connect multiple Docker daemons (hosts) together.
  • Automatically encrypts traffic between nodes in a Swarm.

Creating an Overlay Network 

docker network create -d overlay my_overlay
  • -d overlay specifies the overlay driver.

Connecting Services 

docker service create --name web --replicas 3 --network my_overlay nginx
  • Services can now communicate across nodes transparently.

🔹 Multi-Host Networking Example

  1. Initialize Swarm on the first host: 
docker swarm init --advertise-addr <MANAGER-IP>
  1. Join worker nodes: 
docker swarm join --token <WORKER-TOKEN> <MANAGER-IP>:2377
  1. Deploy a service on the overlay network.
  2. Check communication between replicas across nodes: 
docker service ps web
docker exec -it <container_id> ping <other_container_name>

🔹 Macvlan Networks

  • Allows containers to appear as physical devices on the network.
  • Useful for legacy apps or apps that need direct LAN access.

Example:

docker network create -d macvlan \
  --subnet=192.168.1.0/24 \
  --gateway=192.168.1.1 \
  -o parent=eth0 my_macvlan

🔹 Best Practices

  • Use overlay networks for multi-host apps.
  • Use bridge networks for isolated services on a single host.
  • Avoid exposing all ports publicly.
  • Use VLAN or Macvlan only when necessary for network integration.

🔹 Hands-On Challenge

  1. Create an overlay network.
  2. Deploy a 3-replica Nginx service across Swarm nodes.
  3. Test inter-container communication.
  4. Experiment with Macvlan for a container needing LAN access.

✅ Next Episode: Episode 23 — Docker Swarm Advanced: Services, Secrets & Configs — mastering orchestration features for production-ready deployments.


This content originally appeared on DEV Community and was authored by Yash Sonawane