Because the incoming Ethernet frame has a destination MAC of R1's Ethernet MAC, R1 copies the frame off the Ethernet for processing. If the FCS passes, meaning that the Ethernet frame did not have any errors in it, R1 looks at the Protocol Type field to discover that the packet inside the frame is an IP packet. R1 then discards the Ethernet header and trailer.
Next, R1 looks for the routing table entry that matches the destination address in the packet, 18.104.22.168. The routing table entry is listed in the figure—a route to subnet 22.214.171.124, with outgoing interface Serial0 to next-hop router R2 (126.96.36.199).
Now R1 just needs to build an HDLC frame and send it out its Serial0 interface to R2. As mentioned earlier, ARP is not needed on a point-to-point HDLC WAN link. R1 knows all the information necessary to out the packet inside an HDLC frame and send the frame.
Was this article helpful?