7-2 🌐 Networking (Container Communication)

🌐 Networking (Container Communication)

Docker provides multiple networking options:

• Bridge (default network) → Containers on the same host can talk to each other
• Host → Uses the host network directly (no isolation)
• Overlay → Enables communication across multiple hosts
• None → No network access

Example: Running a container with port mapping for Bridge Network

docker run -p 8080:80 nginx

Maps port 80 of the container to port 8080 of the host.

🔍 Viewing Networks

Command	Description
docker network ls	List all available Docker networks
docker network inspect <network_id_or_name>	Get detailed information about a specific network

🌐 Creating & Removing Networks

Command	Description
docker network create <network_id>	Create a new custom network
docker network rm <network_name>	Remove a specific network

🔗 Connecting & Disconnecting Containers

Command	Description
docker network connect <network_name> <container_name>	Connect a running container to a network
docker network disconnect <network_name> <container_name>	Disconnect a container from a network

🚀 Running Containers with Network Options

Command	Description
docker run --network <network_name> <image>	Start a container in a specific network
docker run --network host <image>	Use the host network (no isolation)
docker run --network none <image>	Start a container with no network access

🔄 Port Mapping & Communication

Command	Description
docker run -p <host_port>:<container_port> <image>	Map container ports to host ports (default bridge network)
docker exec -it <container_id> ping <another_container>	Check communication between containers in the same network

🌐 Docker Networking Examples

Bridge is default:

Docker has built-in DNS server that help container to resolve each other with the name of the container.

🛠️ Practical Example: Creating Custom Network

# Create network
docker network create --driver=bridge --gateway=182.18.0.1 --subnet=182.18.0.0/24 wp-mysql-network 
 
# Create MySQL DB in network
docker run -d --name=mysql-db -e MYSQL_ROOT_PASSWORD=db_pass123 --network=wp-mysql-network mysql:5.6
 
# Create application in network with link to mysql-db
docker run -d --name=webapp -p 38080:8080 -e DB_Host=mysql-db -e DB_Password=db_pass123 --network=wp-mysql-network --link mysql-db:mysql-db kodekloud/simple-webapp-mysql