In Figure 8-3, switch port Fa0/1 will only allow those incoming frames that have source MAC address of MAC A. This port will block traffic with source MAC address of MAC C or any other frame having a source MAC address other than MAC A. Similarly, port Fa0/2 will allow traffic with source MAC address of MAC B only. This port will block all other source MAC addresses including MAC A. Despite the fact that MAC A is allowed on port Fa0/1, it is blocked on port Fa0/2 because secure (allowed) MAC addresses are specific to individual switch ports.