Strict ARP Learning Is Enabled on the Switch, and a User Has Learned the Switch's ARP Entry. Why Cannot the Switch Learn the User ARP Entry by Pinging the User?

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

The firewall installed on a PC may prevent the PC from sending ARP Reply packets after the PC receives ARP Request packets, or the network adapter cannot reply with ARP Reply packets. If either of these situations is the case, the switch cannot receive the Response packet of the ARP Request packet it sends regardless of 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 user's 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.