Docker Networking

Introduction to Docker Networking

Docker creates virtual networks that allow containers to communicate with each other and with the outside world. By default, Docker sets up a bridge network for all containers, but other network types can be used depending on your use case.

Types of Docker Networks

• Bridge: Default network; allows communication between containers on the same host.
• Host: Shares the host’s network stack; best for performance-sensitive workloads.
• Overlay: Enables container communication across multiple Docker hosts (used in Swarm).
• Macvlan: Assigns a MAC address to a container, making it appear as a physical device on the network.
• None: Disables all networking; used for security isolation.

Creating and Inspecting Networks

Create a user-defined bridge network for better control:

docker network create my_network

Inspect details of a network:

docker network inspect my_network

List all Docker networks:

docker network ls

Connecting Multiple Containers

When containers share the same network, they can communicate using container names as hostnames:

docker run -d --name db --network my_network postgres
docker run -d --name app --network my_network myapp

In this setup, app can access the db container using the hostname db.

Networking in Docker Compose

By default, Docker Compose creates a single network for all defined services:

services:
  web:
    build: .
    networks:
      - mynet

  db:
    image: postgres
    networks:
      - mynet

networks:
  mynet:

This allows services to discover each other using service names like db or web.

Troubleshooting Network Issues

• Use docker network inspect to verify connected containers.
• Ping container names to test DNS resolution within the Docker network.
• Use docker exec -it <container> sh or bash to manually test connections.
• Check firewall rules that may block communication between containers.

Docker networking enables seamless communication between containers across environments. Mastering it unlocks the full potential of microservices, distributed applications, and CI/CD systems.