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The ping traffic can now be transmitted with a source MAC address of A
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which is the local machine, destination MAC addresses of C
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in other words PC C the destination MAC address was learnt through ARP
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Source IP address is 10.1.1.1
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destination IP address is 10.1.1.2
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When the hub receives the frame from PC A, it will repeat it
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out of all interfaces except the interface it arrived on.
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So the router will once again receive the frame but will drop it
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because its MAC address is G
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and the destination MAC address for this frame is C.
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PC C will also receive the traffic and will accept it
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because the destination MAC address is C and its local MAC address is C.
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the layer 2 headers will be stripped and the IP address information
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will be read by high layer protocols, this is an ICMP echo packet.
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So the PC will reply with an echo reply message.
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C will send the frame to the hub with the source MAC address of C
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destination MAC address of A it knows the MAC address of A
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because of the previous ARP request message.
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So its ARP cache has a entry associating MAC address A
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with IP address 10.1.1.1 so source Mac address in the frame is c
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destination Mac address is A, source IP address is 10.1.1.2
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destination IP address is 10.1.1.1
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When the frame is receive by the hub
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the hub will repeat it out of all ports
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except the one on which was received.
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The router will receive the frame but will drop it
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because the destination MAC address is A not the G
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the local routers MAC address.
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When A receive the frame from the hub it will accept it
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because the destination MAC address is A and the PC�s Mac address is A,
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it will then strip layer 2 headers
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and forward the information to higher layer protocols.
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In this case it was an echo reply, so the ping will show a success message.
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In other words an echo request was sent to PC C
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and an echo reply message was successfully received back.
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So in my Wireshark capture, for example, I can filter on ICMP messages
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I can see the initial echo request message sent from my PC to 10.0.0.254
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and I can then see the echo reply message.
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Notice please that these are unicast frames.
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Unicast firstly from my PC to the local router
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and then a unicast from the router to my local machine.
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The same information would be displayed if you were pinging
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another local device on the segment.
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As the user you would see something similar to this ping 10.0.0.254
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and the ping was successful.
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So in this example my PC successfully got a reply
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from the remote device that I was pinging.
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