Assume that PC1 and PC2 can communicate with each other. When R1 forwards a data packet sent from PC1 to PC2, which of the following statements are true?
This question tests the difference between Layer 3 addressing and Layer 2 encapsulation during routing. The IP packet originated by PC1 keeps PC1 ' s IP address as its source IP and PC2 ' s IP address as its destination IP as it traverses the routers. Ethernet MAC addresses, however, are rewritten at every routed hop. When R1 forwards the packet across the link toward R2, R1 builds a new Ethernet frame on its outgoing interface. According to the exhibit, R1 ' s outgoing interface on the R1-R2 link uses MAC_C, so MAC_C is the source MAC address. The next-hop device on that link is R2, whose receiving interface uses MAC_D, so MAC_D is the destination MAC address. MAC_A belongs to PC1 and was relevant only on the first local Ethernet segment. MAC_F belongs to PC2 and is used on the final Ethernet segment from R2 to PC2, not on the R1-R2 link. Therefore the correct statements are B and D. The uploaded key B, C is incorrect.
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