After the strict ARP entry learning is enabled, the switch learns only from the Response packet sent in response to locally originated ARP Request packets.

        Firewall installed on the PC may prevent the PC from sending ARP Response packets when receiving ARP Request packets. In this case, the switch cannot receive the Response packet of the ARP Request packet it sends no matter whether the switch sends ping packets to the user or the user sends data packets to the switch to trigger ARP Miss messages. Therefore, the switch cannot learn the users ARP entry.

        If this problem happens on only a few users, configure static ARP entries for the users; if the problem happens on most users, disable strict ARP learning on the switch.