• We start out with a very basic Docker lab to build out confidence.
  • Two plain Nginx containers.
  • Run them on a bridge called test-radiusdesk
  • Reach them on ports 8000 and 8001 respectively from the host Linux system laptop running Docker.

• Create the bridge

docker network create test-radiusdesk
#This was the result
f67e11184a174cf7fb82ba85734dd6d895f0690738cb07246fd7ee13b0024761

• Confirm it was created:

docker network ls
#This was the result
NETWORK ID     NAME                DRIVER    SCOPE
395e31953e3c   bridge              bridge    local
0d8b3aa905bf   host                host      local
17e0830302a8   none                null      local
f67e11184a17   test-radiusdesk     bridge    local

• If you issue the ip a command it will be listed there (Look for the NETWORK ID)

17: br-f67e11184a17: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default 
    link/ether fe:67:4b:58:62:66 brd ff:ff:ff:ff:ff:ff
    inet 172.20.0.1/16 brd 172.20.255.255 scope global br-f67e11184a17
       valid_lft forever preferred_lft forever

• Issue the following commands (We will use docker up first)

# Container 1 -> host port 8000
docker run -d --name nginx-8000 --network test-radiusdesk -p 8000:80 nginx
 
# Container 2 -> host port 8001
docker run -d --name nginx-8001 --network test-radiusdesk -p 8001:80 nginx

• What that does:
  • –network test-radiusdesk plugs both into your custom bridge
  • -p 8000:80 means laptop port 8000 forwards to container port 80

• Use curl or your browser

curl http://localhost:8000
curl http://localhost:8001

• Both should show “Welcome to nginx!”

• Issue this command:

docker exec -it nginx-8000 ping nginx-8001

• It will resolve! On the default bridge this would NOT work.
• Another test:

docker exec -it nginx-8000 curl http://nginx-8001

• Container 8000 reaching container 8001 internally on port 80, without going through your host ports.

• Some handy commands:

docker ps                           # see running
docker network inspect test-radiusdesk  # see which containers + their IPs
docker logs nginx-8000
docker stop nginx-8000 nginx-8001 && docker rm nginx-8000 nginx-8001
docker network rm test-radiusdesk

• Create docker-compose.yml:

services:
  nginx-8000:
    image: nginx
    ports:
      - "8000:80"
    networks:
      - test-radiusdesk

  nginx-8001:
    image: nginx
    ports:
      - "8001:80"
    networks:
      - test-radiusdesk

networks:
  test-radiusdesk:
    driver: bridge

• We can then bring it up with:

docker compose up -d
docker compose down