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DGS-3700-12/DGS-3700-12G Series Layer 2 Gigabit Ethernet Switch User Manual
261
When PC B replies to the ARP request, its MAC address will be written into “Target H/W Address” 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 in a form of Unicast communication.
H/W
type
Protocol
type
H/W
address
length
Protocol
address
length
Operation
Sender
H/W address
Sender
protocol
address
Target
H/W address
Target
protocol
address
ARP reply
00-20-5C-01-11-11 10.10.10.1 00-20-5C-01-22-22 10.10.10.2
Table – 3 (ARP Payload)
When PC B replies the query, the “Destination Address” in the Ethernet frame will be changed to PC A’s MAC
address. The “Source Address” will be changed to PC B’s MAC address (see Table-4).
Destination address Source address
Ether-type ARP FCS
00-20-5C-01-11-11
00-20-5C-01-22-22
Table – 4 (Ethernet frame format)
The switch will also examine the “Source Address” of the Ethernet frame and find that the address is not in the
Forwarding Table. The switch will learn PC B’s MAC and update its Forwarding Table.
Port1 00-20-5C-01-11-11
Port2 00-20-5C-01-22-22
Forwarding Table