Network isolation between services in Docker - Step-by-Step Execution

Process Flow - Network isolation between services

Create Docker Networks

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Assign Services to Networks

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Services Communicate Only Within Same Network

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No Cross-Network Communication Without Explicit Connection

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Isolated Service Groups Achieved

Docker networks are created and services are assigned to them. Services can only talk to others on the same network, isolating communication.

Execution Sample

Docker

docker network create frontend_net

docker network create backend_net

docker run -d --name frontend --network frontend_net nginx

docker run -d --name backend --network backend_net redis

Creates two separate networks and runs frontend and backend services isolated on their own networks.

Process Table

Step	Command	Action	Result
1	docker network create frontend_net	Create network named frontend_net	Network 'frontend_net' created
2	docker network create backend_net	Create network named backend_net	Network 'backend_net' created
3	docker run -d --name frontend --network frontend_net nginx	Start nginx container on frontend_net	Container 'frontend' running on 'frontend_net'
4	docker run -d --name backend --network backend_net redis	Start redis container on backend_net	Container 'backend' running on 'backend_net'
5	Test connectivity frontend -> backend	Ping backend from frontend container	Fails: No route to host
6	Test connectivity backend -> frontend	Ping frontend from backend container	Fails: No route to host

💡 Services are isolated because they are on different Docker networks with no shared connection

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
frontend_net	none	created	created	created	created	created
backend_net	none	none	created	created	created	created
frontend container network	none	none	none	frontend_net	frontend_net	frontend_net
backend container network	none	none	none	none	backend_net	backend_net

Key Moments - 2 Insights

Why can't the frontend container communicate with the backend container?

Because they are attached to different Docker networks (frontend_net and backend_net), which isolates their network traffic as shown in execution_table rows 5 and 6.

Can containers on different networks communicate by default?

No, Docker networks isolate containers by default. Communication requires explicit network connection or shared network, as shown by failed pings in execution_table.

Visual Quiz - 3 Questions

Look at the execution table, what network is the frontend container connected to after step 3?

A backend_net

B bridge

C frontend_net

D none

💡 Hint

Check the 'Result' column in row 3 of the execution_table

At which step does the backend container start running on its network?

A Step 4

B Step 3

C Step 2

D Step 5

💡 Hint

Look at the 'Action' and 'Result' columns for backend container start in execution_table

If both containers were on the same network, what would change in the execution table?

A Networks would not be created

B Ping tests would succeed

C Containers would not start

D No change

💡 Hint

Refer to rows 5 and 6 where ping fails due to network isolation

Concept Snapshot

Docker network isolation:
- Create separate networks with 'docker network create'
- Run containers with '--network' to assign network
- Containers on different networks cannot communicate by default
- Use shared networks or connect containers to multiple networks for communication
- Ensures service isolation and security

Full Transcript

This visual execution shows how Docker network isolation works by creating two networks, frontend_net and backend_net. Containers are started on these networks separately. The frontend container runs on frontend_net and the backend container runs on backend_net. Because they are on different networks, attempts to ping one from the other fail, demonstrating isolation. Variables track network creation and container network assignment. Key moments clarify why containers cannot communicate across networks without explicit connection. The quiz tests understanding of network assignment and communication limits. This teaches how Docker networks isolate services to keep them separate and secure.