# Create network with custom subnet
docker network create \
  --driver bridge \
  --subnet 172.28.0.0/16 \
  --gateway 172.28.0.1 \
  my_network

# Run container on network
docker run -d --name app \
  --network my_network \
  nginx:alpine

services:
  frontend:
    image: nginx:alpine
    networks:
      - public
    ports:
      - "80:80"

  backend:
    image: node:20-alpine
    networks:
      - public
      - private
    expose:
      - "3000"

  database:
    image: postgres:16-alpine
    networks:
      - private  # Internal only

networks:
  public:
    driver: bridge
  private:
    driver: bridge
    internal: true  # No external access

# Containers can reach each other by service name
services:
  app:
    image: myapp
    environment:
      # Use service name as hostname
      DATABASE_HOST: database
      CACHE_HOST: redis

  database:
    image: postgres:16-alpine

  redis:
    image: redis:alpine

# Create encrypted overlay
docker network create \
  --driver overlay \
  --attachable \
  --opt encrypted \
  my_overlay

# Map host:container
docker run -p 8080:80 nginx

# Bind to specific interface
docker run -p 127.0.0.1:8080:80 nginx

# Random host port
docker run -P nginx

# UDP port
docker run -p 53:53/udp dnsserver

# List networks
docker network ls

# Inspect network
docker network inspect my_network

# Test connectivity
docker exec app ping -c 3 database

# Check DNS
docker exec app nslookup backend

# View port mappings
docker port container_name

# Enter container network namespace
docker exec -it app sh

# Check DNS resolution
cat /etc/resolv.conf
nslookup database

# Check connectivity
ping -c 3 backend
curl http://backend:3000/health

Skill("docker-networking")