Dynamic ARP Inspection (DAI) helps prevent ARP spoofing (a common technique used in man-in-the-middle attacks) by ensuring that only valid ARP requests and responses are relayed. The switch checks each ARP packet against a trusted database, either manually configured or dynamically learned, and blocks those packets that have no valid IP-to-MAC address bindings, which effectively prevents attackers from exploiting the network by spoofing ARP messages.

Port Security is insufficient to prevent MAC Spoofing, as the attacker can simply use a spoofed MAC that is whitelisted on the port.