Docker Networking via bridge

 

 

 

Docker Networking 

Docker networks allow containers to communicate with each other.

Example :

 

Frontend Container
        │
        ▼
Backend Container
        │
        ▼
Database Container
  

Without networking:

❌ Containers cannot easily communicate.

With networking:

✅ Containers communicate securely.



In docker networks there are 6 types of networks - 

1) bridge
2) host
3) overlay
4) ipvlan
5) macvlan
6) none


so steps by steps we will learn each and every docker networks.


1. Bridge - Its a default network as a bridge and if we will make container and don't make any other networks so its use by default network as a bridge from our host machine.

So let's see how to verify we have connected through bridge while making container.  if you are followed our docker's blog continuously then you know we have already images ,  container that we are already uploaded.

So, here we will run our docker desktop from our system (in windows search bar search docker desktop) are using our first command  

 

• docker run -it --name server1 ubuntu bash

 

 

 

Here:

• server1  = Container Name
• ubuntu   = Image Name
• bash     = Command to run

Here a ubuntu server is running even you can verify container name via 

• docker ps

Lets verify this docker container is connected via internet.

 

 

 

 

So as you can see the old one images and in that container we are facing some problems to apt-get or apt install iputils-ping -y because we are unable to use ping command.

So we will create new one file, docker images and install manually so follow the steps and do with scratch. 

Step 1: Create a folder

networking-dev/
├── Dockerfile

Step 2: Create Dockerfile

So go to your desire directory in your local machine and then create a folder

mkdir networking-dev

cd networking-dev  

 

and inside the folder open vs code editor  so type a file name without any extension.

code Dockerfile 

add this command and save it simple.

FROM ubuntu:24.04

RUN apt-get update && \
    apt-get install -y \
    iputils-ping \
    net-tools \
    iproute2 \
    dnsutils

CMD ["bash"]

 

This installs:

ping
ifconfig
ip
nslookup
other networking tools

Step 3: Build your image

Go inside the folder containing the Dockerfile: 

 

• docker build -t atul/networking-dev .

 

 

 

 
Notice the . at the end.

Docker will:

• Read the Dockerfile
• Download Ubuntu 24.04
• Install ping, net-tools, iproute2, dnsutils
• Create image atul/networking-dev

Verify:

docker images

You should see:

REPOSITORY           TAG
atul/networking-dev  latest

 

 

 

Run container

Now lets move into our real purpose of this blog docker networking via bridge

So, here we will run our docker desktop from our system (in windows search bar search docker desktop) are using our first command  

 

• docker run -it --name server1 atul/networking-dev

Previously we have server1 in container docker desktop so delete it. 

Inside container test:

ping google.com
ifconfig
ip addr
nslookup google.com

All should work.

• docker ps 

C:\Users\user\Desktop\app>docker ps
CONTAINER ID   IMAGE                 COMMAND   CREATED         STATUS         PORTS     NAMES
98acba8d0340   atul/networking-dev   "bash"    4 minutes ago   Up 4 minutes             server1

C:\Users\user\Desktop\app>

Verify which network a container is using

Run:

• docker inspect server1

Large output will appear.

To see only network information:

• docker inspect server1 --format='{{json .NetworkSettings.Networks}}'

Output:

{"bridge":{"IPAddress":"172.17.0.1"}}

This means:

Container: server1
Network: bridge
IP: 172.17.0.1

Practical Demo

Create two containers:

• docker run -dit --name server1  atul/networking-dev
• docker run -dit --name server2  atul/networking-dev

Check:

docker ps

After creating server in another terminal lets check IP address even try to ping each other

hostname -I 

ping 172.17.0.2 

We are able because both are connected with docker network by default bridge.

Enter server1:

docker exec -it server1 bash

Try:

ping server2

On the default bridge network, name resolution may not work as expected.

 

root@98acba8d0340:/# ping server2
ping: server2: Name or service not known
root@98acba8d0340:/#

 

we are not able to ping because of they are only default network as an IP address.

 A better practice is creating your own network: so for this open new terminal and run this command 

• docker network create mynetwork

open another terminal and type this command with server3 and --network mynetwork

 

hostname -I 

you can see the IP there is -  172.18.0.2 but this is in another class - 18 and previous one are in 17 class

Now we want to connect server 1 with my network mynetwork

and you can see in server1 having two different class IP

 

 

now we are able to run using name 

 

 

 

 

These are commands that we have used 

docker network ls
docker inspect server1
docker network create mynetwork
docker run --network mynetwork ...

Conclusion

Understanding Dockerfiles, custom image creation, and environment variables is essential for anyone learning Docker, DevOps, Cloud Computing, or System Administration.

By mastering these concepts, you'll be able to create reusable Docker images, automate deployments, and configure applications efficiently. These skills are widely used in real-world production environments and are frequently asked about in DevOps and System Engineer interviews.