Yet Another Short-Lived Ethernet Frame

Yet Another Short-Lived Ethernet Frame

Just like Hannah and R1 before it, R2 needs to send an IP packet across an Ethernet. It knows the source and destination IP addresses in the packet because those haven't changed during this whole process. R2 knows its own Ethernet address on the outgoing interface. All R2 needs to know is the MAC address that corresponds to the web server so it can finish building the Ethernet frame and send the frame to the web server.

To find the web server's Ethernet MAC address, R2 uses the same ARP protocol messages as did Hannah and R1. R2 sends an ARP broadcast, looking for the Ethernet address of host 130.4.3.3 (web server). After the web server replies with an ARP reply, R2 can finish building the Ethernet frame and forward it.