When deploying applications using containers, networking plays a critical role in defining how containers communicate with each other and with the outside world. While Docker provides simple networking out of the box, complex production environments often require custom networks, controlled isolation, and fine-grained connectivity.

This post explores advanced Docker networking, focusing on creating and managing custom networks such as bridge, overlay, and macvlan, and offers practical use cases to improve security, scalability, and observability in containerized systems.

Docker Networking Basics Recap

Docker supports several built-in network drivers:

Driver Description
bridge Default local network for containers on a host
host Shares host network stack (no isolation)
none Disables networking entirely
overlay Enables communication across multiple hosts
macvlan Assigns MAC address directly to container

For production environments, we focus primarily on bridge, overlay, and macvlan.

Creating Custom Bridge Networks

A bridge network allows containers on the same host to communicate securely and with custom DNS and subnetting options.

docker network create \
--driver bridge \
--subnet 192.168.100.0/24 \
--gateway 192.168.100.1 \
custom-bridge

Attach containers to this network:

docker run -d --name app1 --network custom-bridge nginx
docker run -d --name app2 --network custom-bridge alpine sleep 3600

Then from app2:

docker exec -it app2 ping app1

This allows container-to-container DNS resolution without exposing services externally.

Overlay Networks for Multi-Host Clusters

To span containers across multiple Docker hosts, use overlay networks with Docker Swarm or Kubernetes.

Enable Swarm mode:

docker swarm init

Create an overlay network:

docker network create \
--driver overlay \
--attachable \
app-overlay

Deploy services to this network:

docker service create \
--name web \
--network app-overlay \
nginx

Overlay networks allow for global service discovery, load balancing, and secure tunneling between hosts.

macvlan Networks for L2 Isolation

macvlan networks allow containers to appear as physical devices on the network — useful for legacy applications or network appliances.

Create a macvlan network:

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

Run a container on this network:

docker run -d --name legacy-app --network macvlan-net nginx

This container will now be accessible from your local LAN as a first-class network citizen.

Inspecting and Managing Networks

List all networks:

docker network ls

Inspect a specific network:

docker network inspect custom-bridge

Disconnect or reconnect containers:

docker network disconnect custom-bridge app1
docker network connect app-overlay app1

Remove unused networks:

docker network prune

Networking in Docker Compose

Define custom networks in docker-compose.yml:

version: "3"
services:
web:
image: nginx
networks:
- frontend

api:
image: my-api
networks:
- backend

networks:
frontend:
driver: bridge
backend:
driver: bridge

Compose will automatically create isolated networks and link containers accordingly.

Best Practices for Docker Networking

  • Use custom bridge networks to isolate microservices
  • Use overlay networks in distributed systems (Swarm/Kubernetes)
  • Avoid host mode unless required for performance
  • Monitor network usage with tools like cAdvisor, Weave Scope, or Docker stats
  • Prefer internal-only networks for backend communication
  • Leverage firewall rules and routing tables for extra security

Real-World Use Cases

  • Microservices Architecture: Isolate services into networks per domain (e.g., auth, billing)
  • Hybrid Cloud: Overlay networks for services across on-prem and cloud
  • Legacy Integration: macvlan for containers interacting with non-container systems
  • CI/CD Pipelines: Create ephemeral networks per test run to simulate production isolation

Conclusion

Understanding and managing Docker networking at an advanced level is essential for deploying secure, scalable containerized applications. Whether you’re isolating microservices, connecting containers across clusters, or integrating with legacy systems, custom Docker networks give you full control over inter-container communication.

Master these networking patterns to build resilient, production-grade platforms that scale confidently across environments.