Docker Networking Skill
Master Docker networking concepts and configuration for container communication, service discovery, and network isolation.
Purpose
Configure and troubleshoot Docker networks for development and production environments with proper isolation and service discovery.
Parameters
| Parameter | Type | Required | Default | Description |
|---|
| driver | enum | No | bridge | bridge/overlay/host/macvlan |
| subnet | string | No | - | Custom subnet CIDR |
| internal | boolean | No | false | Internal-only network |
Network Drivers
| Driver | Use Case | Multi-Host | Encryption |
|---|
| bridge | Single host, default | No | No |
| overlay | Swarm, multi-host | Yes | Optional |
| host | Max performance | No | N/A |
| macvlan | Physical network | No | No |
| none | Disable networking | No | N/A |
Configuration Examples
Custom Bridge Network
# 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
Docker Compose Networking
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
Service Discovery
# 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
Overlay Network (Swarm)
# Create encrypted overlay
docker network create \
--driver overlay \
--attachable \
--opt encrypted \
my_overlay
Port Mapping
# 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
Error Handling
Common Errors
| Error | Cause | Solution |
|---|
network not found | Typo or deleted | Create network |
address in use | Port conflict | Change port |
cannot reach | Wrong network | Check network membership |
DNS failed | Service not ready | Add health checks |
Fallback Strategy
- Verify network exists:
docker network ls - Check container membership:
docker network inspect <net> - Test DNS:
docker exec app nslookup backend
Troubleshooting
Debug Checklist
- Network created?
docker network ls - Container connected?
docker inspect <container> - DNS resolving?
nslookup from container - Port mapped?
docker port <container>
Diagnostic Commands
# 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
Network Debugging
# 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
Usage
Skill("docker-networking")
Related Skills
- docker-compose-setup
- docker-swarm
