According to theFortiSwitchOS 7.6 Administration Guideand theFortiSwitch 7.6 Study Guide, Dynamic ARP Inspection (DAI) is a security feature used to intercept, log, and discard ARP packets with invalid IP-to-MAC address bindings. DAI is primarily used to prevent " Man-in-the-Middle " attacks, such as ARP spoofing or ARP cache poisoning.
In this scenario, DAI is active on VLAN 10. When DAI is enabled, the FortiSwitch intercepts all ARP packets on untrusted ports and validates them against a trusted source-most commonly theDHCP snooping database.
As shown in the " DHCP Snooping database " exhibit, PC2 is correctly mapped to IP 10.0.10.30 and MAC 00:
09:0F:AB:00:0B.
When PC2 attempts to send a forged ARP reply claiming that IP 10.0.10.254 (the FortiGate ' s IP) is located at its own MAC address (00:09:0F:AB:00:0B), the FortiSwitch ' s DAI engine inspects the packet. It checks the DHCP snooping database for a binding that matches IP 10.0.10.254 to MAC 00:09:0F:AB:00:0B. Finding no such valid entry (because the database correctly identifies the MAC 00:09:0F:AB:00:0B as belonging to IP
10.0.10.30), the switch identifies the ARP packet as illegitimate.
Consequently, the FortiSwitch willdrop the ARP repliesbecause they fail the DAI validation check against the established DHCP snooping bindings. Option A is incorrect as DAI functions independently of IPSG once the database is populated. Option B is incorrect because " accepting " the spoofed packet is the opposite of DAI ' s purpose. Option C is incorrect because DAI is specifically designed to run on untrusted ports to protect the network from client-side attacks.