I have the following 3 devices on my network(a bus topology): A,B,C


MAC(i) - denote the MAC address of the device i.
IP(i) - denote the IP address of the device i.

The devices B and C happen to have the following configuration:
MAC(B) == MAC(C) [I know it's very rare, but lets say B spoofed C's MAC]
IP(B) != IP(C)

A(has different mac and ip address from B,C) sends out a frame with
Destination MAC address = MAC(B) [which is == MAC(C)]
Destination IP address = IP(C)

Will C recieve the frame or will it be ambiguous? A nice explanation would be highly appreciated.

  • Smells like homework. What do you think will happen? – Ron Trunk Sep 3 '17 at 14:58
  • I think may be that the frame will be stripped off using MAC address at the data link layer, both at B and C. But the network layer at B would reject the frame, because it doesn't match the IP address. Not exactly homework, it was in my exam and I wish to know the solution : ) – Dipunj Sep 3 '17 at 15:02
  • Exam questions are explicitly off topic here. Instead of thinking about what layers do, think about what individual hosts do. – Ron Trunk Sep 3 '17 at 15:46
  • @RonTrunk i discussed it with my peers and searched the internet for it, but Nowadays no one actually uses OSI, so I thought of asking it here. – Dipunj Sep 3 '17 at 15:48
  • Layers don't do anything. They're just a mental model. Ethernet and IP are real protocols that have specific responses. Concentrate on that. – Ron Trunk Sep 3 '17 at 21:48

It depends on what is connecting the devices.

If it is a hub then the frame will be delivered to both B and C.

If it is a switch then the frame will be delivered to whichever of B or C most recently sent a frame to the switch.

If the frame arrives at C it will be processed normally.

If the frame arrives at B then asuming B is configured an end node it will probably drop it. If B is configured as a router then it may try to route the packet. This may end up with a duplicate packet arriving at C.

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