packet from User B is sent to Ethernet 1/0/4, the switch records the association between the MAC
corresponding port to the MAC address table of the switch.
ng diagram (3)
address of User B and the
Figure 18-4
MAC address learni
At this time, the MAC address table of the switch includes two forwarding entries shown in
4)
Figure
18-5
. When forwarding the response packet, the switch unicasts the packet instead of
ecause MAC-A is already in the MAC address
of the switch (2)
broadcasting it to User A through Ethernet 1/0/1, b
table.
Figure 18-5
MAC address table entries
Port
VLAN ID
MAC-address
Ethernet1/0/1
1
MAC-A
Ethernet1/0/4
1
MAC-B
) After this interaction, the switch directly unicasts the packets destined for User A and User B based
rresponding MAC address table entries.
5
on the co
z
B is unreachable or User B receives the
z
The switch learns only unicast addresses by using the MAC address learning mechanism but
directly drops any packet with a broadcast source MAC address.
Under some special circumstances, for example, User
packet but does not respond to it, the switch cannot learn the MAC address of User B. Hence, the
switch still broadcasts the packets destined for User B.
Managing MAC Addr
A
timer for an entry when dynamically creating
ess Table
ging of MAC address table
To fully utilize a MAC address table, which has a limited capacity, the switch uses an aging mechanism
for updating the table. That is, the switch starts an aging
18-3