D-Link DES-3550 Product Manual - Page 282

Forwarding Table, Table - 3 ARP Payload, Table - 4 Ethernet frame format

Page 282 highlights

xStack® DES-3500 Series Layer 2 Stackable Fast Ethernet Managed Switch User Manual 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 Protocol H/W Protocol Operation Sender type type address address length length 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. Forwarding Table Port1 00-20-5C-01-11-11 Port2 00-20-5C-01-22-22 267

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xStack
®
DES-3500 Series Layer 2 Stackable Fast Ethernet Managed Switch User Manual
267
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