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

Exercise 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.

Show example solution

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

Test yourself

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
- ping isn't installed
Show answer

There's no DNS resolution by container name on the default bridge — Name-based access needs a user-defined network.

Create a new network.

docker network ____ uygulama-agi

Show answer

docker network create uygulama-agi

Match.

default bridge

No DNS by name
user-defined bridge

Built-in DNS
--subnet

IP range
network prune

Remove unused ones

Next lesson: Container connectivity

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