xStack® DGS-3420 Series Layer 2 Managed Stackable Gigabit Switch CLI Reference Guide
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request is sent via broadcast, the “Destination address” is in a format of Ethernet broadcast (FF-
FF-FF-FF-FF-FF).
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.
