D-Link DGS-3426P Product Manual - Page 401

Figure 2 xStack® DGS-3400 Series Layer 2 Gigabit Ethernet Managed Switch When the switch floods the frame of ARP request to the network, all PCs will receive and examine the frame but only PC B will reply the query as the destination IP matched (see Figure 3). Figure 3 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 an Ethernet frame again and sent back to the sender. The ARP reply is in a form of Unicast communication. Table 3. ARP Payload H/W Protocol Type Type H/W Address Length Protocol Address Length Operation ARP reply Sender H/W Address 00-20-5C-01-11-11 Sender Protocol Address 10.10.10.1 Target H/W Address 00-00-00-00-00-00 Target Protocol Address 10.10.10.2 When PC B replies to 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). Table 4. Ethernet Frame Format Destination Address 00-20-5C-01-11-11 Source Address 00-20-5C-01-22-22 Ether-Type ARP FCS 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. 392