What does `dev eth0` signify?

In networking commands, dev is short for device, and it is used to specify which network interface you want to apply the configuration to.

Here’s a breakdown of dev eth0:

1. dev (Device): This tells the ip command that the following argument is the name of the network hardware interface (physical or virtual).
2. eth0: This is the standard name for the first Ethernet interface in Linux. In a Docker container, eth0 is the virtual network card that connects the container to the Docker network (lab_net).

Why do we need it?

A computer (or container) can have multiple network interfaces. For example:

• lo: The loopback interface (localhost).
• eth0: The connection to the local network or internet.
• eth1: A second network connection.

By typing dev eth0, you are explicitly telling Linux: "Take this IP address (192.168.56.10) and assign it specifically to the eth0 card."

Without specifying the device, the system wouldn't know where to "plug in" the new IP address