MITM Attacks with ARP Poisoning and how to defend against ARP Poisoning

In the first link will be described what an Man In The Middle (MITM) is, and how something works with ARP Poisoning.
These info can be found here: http://gwallgofi.com/mitm-attack

The second link will describe how you can defend against ARP Poisoning on Linux systems by creating a script that will let you make use of static ARP entries, so they can’t change anymore without your knowledge, and will protect you against this kind of attacks.
These info can be found here: http://gwallgofi.com/static-arp-linux