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Yash Sonawane
Yash Sonawane

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

#docker #devops #tutorial #networking

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
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  • -d overlay specifies the overlay driver.

Connecting Services 

docker service create --name web --replicas 3 --network my_overlay nginx
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  • 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>
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  1. Join worker nodes: 
docker swarm join --token <WORKER-TOKEN> <MANAGER-IP>:2377
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  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>
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🔹 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
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🔹 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.

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