I require this program, but doesn't come in the system since Debian 9 codename "Stretch".
$ apt-cache search net-tools
$ apt-cache show net-tools
$ dpkg -l | grep net-tools
$ sudo apt-get install net-tools

Usage:
# ifconfig
# sudo ifconfig <ETHERNET OR WIFI>
$ man ifconfig

References:
Guide: Basic networking
Guide: Iproute2
