D-Link xStack DGS-3420 Series Reference Manual page 401

xStack® DGS-3420 Series Layer 2 Managed Stackable Gigabit Switch Web UI Reference Guide
Figure 3 - Ethernet Frame Format
When 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 into its Forwarding
Table.
Figure 4 – Forwarding Table
In addition, when the switch receives the broadcasted ARP request, it will flood the frame to all ports except the
source port, port 1 (see Figure 5).
Figure 5 –Broadcast Request
When PC B replies to the ARP request, its MAC address will be written into "Target H/W Address" in the ARP
payload (see Figure 6). The ARP reply will be then encapsulated into an Ethernet frame again and sent back to the
sender. The ARP reply is in a form of Unicast communication.
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