DevOps Classroom notes 16/Dec/2025

Networking in docker

• Docker networking model follows a specification called as CNM (Container Networking Model)
• Docker networking supports
  • Single Host
  • Multi Host
• Lets Discuss Single Host
• Docker supports Network drivers. The network drivers are
  • Null
  • HOST
  • BRIDGE
  • OVERLAY (multihost)
• Creating a bridge network

docker network create -d bridge --subnet 10.255.0.0/24 my_bridge

• running the container on the created network

docker run -d -P  --net my_bridge  nginx

• All the containers attached a same network can communicate with each other using ip addresses.
• Lets create two containers in default bridge

docker run -d --name b1 alpine sleep 1d
docker run -d --name b2 alpine sleep 1d

• Lets get ipaddress of b1 and b2

docker network inspect bridge

• we got ips as 172.17.0.2 and 172.17.0.3
• lets ping b2 from b1 using ip
  
• lets ping b2 from b1 using name
  
• Lets create two containers in custom bridge

docker run -d --name c1 --net my_bridge alpine sleep 1d
docker run -d --name c2 --net my_bridge alpine sleep 1d

• Lets get ip address of c1 and c2

docker network inspect my_bridge

• we got 10.255.0.2 and 10.255.0.3
• lets ping c2 from c1 using ip and name
  
• IN default bridge network, name resolution is not enabled, where as in custom defined bridge network, name resolution is enabled.

Lets create a database and application.

• Create a bridge network

docker network create -d bridge --subnet 10.200.0.0/24 nop_net

• create a volume

docker volume create nopdb

• Now lets create mysql container with name nopdb

docker run -d \
  --name nopdb \
  -v nopdb:/var/lib/mysql \
  -e MYSQL_ROOT_PASSWORD=root123 \
  -e MYSQL_DATABASE=nop \
  -e MYSQL_USER=nop \
  -e MYSQL_PASSWORD=nop \
  --net nop_net \
  mysql:8.0

• Now lets run nop server shaikkhajaibrahim/june-nop

docker run -d \
   --name nop \
   -P \
   --net nop_net \
   shaikkhajaibrahim/june-nop

• To simplify executing these many commands docker uses docker compose
• Refer Here for docker compose referenc
• create a yaml file with name docker-compose.yml

services:
    db:
      image: mysql:8.0
      environment:
        - MYSQL_ROOT_PASSWORD=root123
        - MYSQL_DATABASE=nop
        - MYSQL_USER=nop
        - MYSQL_PASSWORD=nop
      volumes: 
        - nopdb:/var/lib/mysql
      networks: 
        - nop-net

    nop:
      image: shaikkhajaibrahim/june-nop
      networks: 
        - nop-net
      ports: 
        - 33000:5000
networks:
  nop-net:

volumes:
  nopdb:

• We would discuss about compose after yaml.

Exercise:

• I want you to figure out a way to create a container
  • with max of 0.5 cores
  • with max of 256 MiB RAM