Networks

Docker · Reference cheat sheet

📋 Overview

Docker networks connect containers. Compose creates a default network so services resolve each other by service name as DNS.

🔧 Core concepts

💡 Examples

Inspect defaults:

docker network ls
docker network inspect bridge

User-defined bridge:

docker network create appnet
docker run -d --name db --network appnet postgres:16-alpine
docker run -d --name api --network appnet -p 9000:9000 myapi

Compose networks:

services:
  api:
    networks: [frontend, backend]
  db:
    networks: [backend]
networks:
  frontend:
  backend:
    internal: true

⚠️ Pitfalls

• Using host localhost to reach another container fails — use DNS name.
• Publishing every port widens attack surface — only publish what you need.
• host network mode breaks container isolation assumptions.

🔗 Related

• compose.md
• getting_started.md
• healthchecks.md
• volumes.md