1-2 
Figure 1-1 MAC address learning diagram (1) 
 
 
Figure 1-2 MAC address table entry of the switch (1) 
 
 
2)  After learning the MAC address of User A, the switch starts to forward the packet. Because there is 
no MAC address and port information of User B in the existing MAC address table, the switch 
forwards the packet to all ports except GigabitEthernet 1/0/1 to ensure that User B can receive the 
packet. 
Figure 1-3 MAC address learning diagram (2) 
 
 
3)  Because the switch broadcasts the packet, both User B and User C can receive the packet. 
However, User C is not the destination device of the packet, and therefore does not process the 
packet. Normally, User B will respond to User A, as shown in 
Figure 1-4. When the response 
packet from User B is sent to GigabitEthernet 1/0/4, the switch records the association between the 
MAC address of User B and the corresponding port to the MAC address table of the switch.