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Let me first to tell me what I know, please correct me if I am wrong.

I know when Ethernet frame travels across the internet then Layer 3 data (Source and Destination IP) remains same and Layer 2 data(Source And Destination MAC) keep changing from Hop to Hop.

So, When the frame from A will reach to Destination B, then it will have this data:

-> IP Address Source - IP of Sender(A)

-> IP Address of Destination - IP of Receiver(B)

-> MAC Address of Source - Last Hop(Router) MAC Address

-> MAC of Destination - MAC Address of Receiver(B)

So, Frame reached B has MAC Address of Last Hop(Router) as Source MAC, But actual Source MAC Address is the MAC Address of A. So I want to know is it possible for B to know MAC Address of Actual Source(A)?

PS: Please change Tags, I am new to networking So doesn't know which domains this question covers.

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So, Frame reached B has MAC Address of Last Hop(Router) as Source MAC, But actual Source MAC Address is the MAC Address of A. So I want to know is it possible for B to know MAC Address of Actual Source(A)?

A frame can only be used between nodes within the same layer-2 segment, it cannot travel beyond. A packet transported in a frame can be forwarded outside the segment/subnet by a router. A router generally strips the received frame and generates a new one for the transported packet.

So, the frame that is received by the final destination is the one generated by its local gateway - it didn't exist before that.

Neither can the destination learn the MAC address of the original IP source nor is that of any consequence to it. In fact, the original source may not even have used a MAC address at all as not all networks use those.

  • Thank you, sir, for Answering, But if the only packet travels from the router, then if the IP address of my router changes somehow(Tor), will it be able to receive a response? Because Now Packet has only IP Address, How server going to locate my Router. – Anonymous Sep 8 at 6:09
  • Changing IP addresses with NAT doesn't change the situation regarding MAC addresses. Tor works in the application layer (off-topic here) and is something different altogether (it doesn't propagate MAC addresses beyond their segment either). – Zac67 Sep 8 at 7:29

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