What Hannah and R1 Know Before Using ARP

For Hannah to learn what R1's Ethernet MAC address is, she just needs to ask R1. Hannah does so by sending an ARP broadcast. An ARP broadcast is a message that simply says, "Hey, if this is your IP address, tell me your Ethernet MAC address." It's called a broadcast because the destination MAC address of the ARP broadcast is the Ethernet broadcast address of FFFF.FFFF.FFFF. Because switches forward LAN broadcasts to all devices in the network, everyone on the LAN gets the ARP broadcast.

Each IP host on the LAN examines the ARP broadcast, but only R1 has IP address 8.1.1.250 configured, so it is the only one that should reply. Figure 11-7 shows the basic process.