Host_A pings Host_B through one router (Figure 9.2). Step through all 36 steps and watch where the work happens, which layer is active, and which fields in the packet and frame change. MAC addresses are the ones from the chapter's output.
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Which layer is working
What the device is holding
Lookup or check in this step
Key idea. The IP packet keeps the same source and destination addresses from end to end. Only the frame is rebuilt at each hop, so the destination MAC is always the next device on the local network, here the default gateway on the way out. Frames are never placed on a remote network. A bigger network repeats the same steps with more hops.