Master Docker Container Networking: 3 Methods and Practical Link Examples

1. System Environment

Server version: CentOS Linux release 7.4.1708 (Core); Docker version: 20.10.12; CPU architecture: x86_64.

2. Docker Container Interconnection Overview

2.1 Three ways to connect containers on the same host

Use the container's IP address directly (hard‑coded IPs are not portable and may change on restart).

Use the host IP plus the container's exposed port (limited to services listening on that port).

Use Docker's link mechanism, which allows containers to discover each other by name and securely share connection information.

2.2 Using docker --link : precautions

The linked container must be running.

The container that creates the link must also be running.

The host IP of the linked container does not need to be fixed; Docker updates /etc/hosts with a new alias each time.

2.3 Principle of docker --link

The link adds name‑to‑IP mappings in /etc/hosts, enabling name‑based communication between containers.

3. Docker Container Interconnection

3.1 Communicating via container IP address

Create a MySQL container:

# docker run -dit --restart=always --name=mysql5 -e MYSQL_ROOT_PASSWORD=123456 -p 3306:3306 hub.c.163.com/library/mysql:latest

Inspect its IP address:

# docker inspect mysql5 | grep -i ipaddr
"IPAddress": "172.17.0.4",

Start a CentOS container and ping the MySQL container:

# docker run -it --restart=always --name=centos7 hub.c.163.com/library/centos:latest ping 172.17.0.4

3.2 Communicating via --link parameter

Docker allows inter‑container communication by default; it can be disabled with -icc=false. When disabled, use --link name:alias to connect specific containers.

Create a CentOS container linked to MySQL:

# docker run -it --restart=always --name=c7 --link mysql5:mysql hub.c.163.com/library/centos:latest ping mysql

Enter the container and ping by name:

# docker exec -it c7 /bin/bash
# ping mysql

Install a MySQL client inside the CentOS container (MariaDB client works for MySQL): # yum -y install mariadb Connect to the MySQL server from the CentOS container: # mysql -uroot -p123456 -h 172.17.0.4 After successful login, you can list databases and perform queries.