On my school network, using wireshark to see network traffic (filter=arp), I only see gratuitous packets. Meaning, all hosts on network send gratuitous packets (ex: gratuitous for 10.10.3.54, gratuitous for 10.10.3.59, etc). I believe this technic is used to counter mitm attacks. Is it really? why?, if it is still vulnerable to mitm attack, why? How could you prevent it then?. Note, when I say mitm attack, I usually reffer to arp poisonning.
Using nmap and scanning the subnet 10.10.3.0, there is no results (I only see my ip). I tried no ping, quick scan, intensive scan). Yes, my command started with 10.10.3.0/24.