Whe
n the switch receives the frame, it will check the “Source Address” in the Ethernet frame’s header. If the address is not in its
Forwarding Table, the switch will learn PC A’s MAC and the associated port and enter them in its Forwarding Table.
Port1 00-20-5C-01-11-11
Forwarding Table
In a
ddition, when the switch receives the broadcasted ARP request, it will flood the frame to all ports except the source port, port
1 (see Figure -2).
Figure - 2
When the switch floods the frame of the ARP request to the network, all PCs will receive and examine the frame but only PC B
will reply to the query because the destination IP matches (see Figure-3).
Figure - 3
When PC B replies to an ARP request, its MAC address will be written into the “Target H/W Address” table in the ARP payload
shown in Table-3. The ARP reply will be then encapsulated into the Ethernet frame again and sent back to the sender. The ARP
reply is the form of a Unicast communication.
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