How Docker Networking Works on a VPS

Docker networking controls how containers communicate with each other, the host system, and the public internet. Understanding this is critical for exposing services securely on a VPS.

Step 1: Understand Docker Network Types

Docker uses different network drivers depending on your setup.

bridge   → default local container networking
host     → container shares host network
none     → no networking
overlay  → multi-host (Swarm / cluster)

Most VPS setups rely on the bridge network.

Step 2: List Existing Docker Networks

View all available Docker networks.

docker network ls

The default bridge network is usually named bridge.

Step 3: Inspect a Docker Network

Inspect network details such as IP ranges and connected containers.

docker network inspect bridge

This shows container IPs, gateways, and subnet configuration.

Step 4: How Containers Access the Internet

Containers use NAT through the host to reach external networks. Docker automatically configures iptables rules for this.

iptables -t nat -L -n

Outbound traffic is masqueraded through the VPS public IP.

Step 5: Expose Container Ports to the VPS

Port mapping allows external access to containers.

docker run -d -p 80:3000 my-app

Traffic on port 80 of the VPS is forwarded to port 3000 inside the container.

Step 6: Container-to-Container Communication

Containers on the same network can reach each other by name.

docker network create app-network
docker run -d --name api --network app-network api-image
docker run -d --name web --network app-network web-image

The web container can reach api using its name.

Step 7: Common Docker Networking Issues on VPS

Typical problems include blocked ports, firewall conflicts, or incorrect bindings.

ss -tulnp
docker ps
docker inspect container_name

You may also want to review this related article: How to Fix Services That Fail After Server Reboot

Optional Step: Use a Reverse Proxy Instead of Port Mapping

For multiple containers, a reverse proxy simplifies networking.

docker run -d -p 80:80 nginx

This allows multiple services to share standard ports cleanly.