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Bridge network

Learn to create a custom bridge network.

The bridge network

Containers with no network specified are attached to the default bridge network. On this network containers can reach each other by IP but not by name (there's no DNS). User-defined bridge networks offer built-in DNS: a container's name is its host name for the others on the network:

docker network create uygulama-agi
docker run -d --name db --network uygulama-agi -e POSTGRES_PASSWORD=gizli postgres:16
docker run --rm --network uygulama-agi alpine ping -c 1 db
# PING db (172.19.0.2): 56 data bytes

Network creation options

When creating a network, the subnet and gateway can be chosen by hand; handy to avoid ranges clashing with the company network. Unused networks can be removed:

docker network create --driver bridge --subnet 10.50.0.0/24 --gateway 10.50.0.1 ozel-ag
docker network rm ozel-ag
docker network prune -f

Practice Access by name

Write three commands: create the uygulama-agi network; start a container named cache from redis:7 in the background on this network; in an alpine container deleted when done, run ping -c 1 cache on the same network.

Starter code

terminal
# buraya yaz

Sample solution

terminal
docker network create uygulama-agi
docker run -d --name cache --network uygulama-agi redis:7
docker run --rm --network uygulama-agi alpine ping -c 1 cache

Expected output

5e6f708192a3…
f8091a2b3c4d
PING cache (172.19.0.2): 56 data bytes
64 bytes from 172.19.0.2: seq=0 ttl=64 time=0.112 ms

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Why doesn't ping db work on the default bridge network?

  • The port isn't published
  • db has stopped
  • There's no DNS resolution by container name on the default bridge Correct answer
  • ping isn't installed

Explanation: Name-based access needs a user-defined network.

2 Create a new network.

Question 
docker network ____ uygulama-agi
Answer 
docker network create uygulama-agi

Explanation: The default driver is bridge.

3 Match.

Term Meaning
default bridge No DNS by name
user-defined bridge Built-in DNS
--subnet IP range
network prune Remove unused ones

All lessons in Beginner

1 What is Docker?

  1. What is Docker?
  2. Containers and virtual machines
  3. Images and containers
  4. Docker architecture
  5. Use cases
  6. Summary - What is Docker

2 Installation and first commands

  1. Installing Docker
  2. docker version
  3. docker info
  4. The hello-world container
  5. Docker Desktop
  6. Summary - Installation

3 First container

  1. docker run basics
  2. Running in the background
  3. docker ps
  4. docker stop and rm
  5. docker logs
  6. Summary - First container

4 Dockerfile basics

  1. What is a Dockerfile?
  2. The FROM instruction
  3. The RUN instruction
  4. COPY and ADD
  5. CMD and ENTRYPOINT
  6. Summary - Dockerfile

5 Build and images

  1. docker build
  2. Tagging images
  3. Build context
  4. Layers and cache
  5. .dockerignore
  6. Summary - Build

6 docker run options

  1. Interactive mode
  2. Naming containers
  3. Restart policy
  4. Working directory
  5. Switching users
  6. Summary - docker run

7 Image management

  1. docker images
  2. docker rmi
  3. docker pull
  4. docker push
  5. docker tag
  6. Summary - Image management

8 Port mapping

  1. The port concept
  2. The -p flag
  3. Multiple ports
  4. Random ports
  5. IP binding
  6. Summary - Port mapping

9 Volumes and data

  1. Data persistence
  2. Named volumes
  3. The -v flag
  4. Bind mounts
  5. Volume management
  6. Summary - Volumes

10 Environment variables

  1. The -e flag
  2. The ENV instruction
  3. The ARG instruction
  4. env-file
  5. The WORKDIR instruction
  6. Summary - Environment

11 Project: docker-compose

  1. Compose design
  2. Service definition
  3. Database service
  4. Volume and network
  5. Putting it together - compose

12 Docker Hub and registry

  1. What is Docker Hub?
  2. docker login
  3. Searching images
  4. Official images
  5. Private registry
  6. Summary - Registry

13 Network basics

  1. Network drivers
  2. docker network ls
  3. Bridge network
  4. Container connectivity
  5. Publishing ports
  6. Summary - Network

14 Beginner final

  1. Challenge - Dockerfile
  2. Challenge - Build and run
  3. Challenge - Volume
  4. Challenge - Compose
  5. Challenge - Beginner project