Install arpwatch by entering the following commands in the terminal:
sudo apt update sudo apt install arpwatch
Description:
Ethernet/FDDI station activity monitor
Arpwatch maintains a database of Ethernet MAC addresses seen on the network, with their associated IP pairs. Alerts the system administrator via e-mail if any change happens, such as new station/activity, flip-flops, changed and re-used old addresses. . If you want to maintain a list authorized MAC addresses manually, take a look at the arpalert package which may fit your needs better.
Homepage: http://ee.lbl.gov/
Version: 2.1a15-6
Section: universe/admin