Hannah Sending an ARP Broadcast, Looking for 8.1.1.250's Ethernet Address

In Figure 11-7, all other IP hosts on the LAN receive the ARP broadcast because the switch floods the frame out all physical interfaces except the port connected to Hannah. Because everyone in network 8.0.0.0 should be somewhere on this Ethernet, if IP address 8.1.1.250 exists, then that device should get the ARP request.

The ARP broadcast lists the IP address for which it is searching for the corresponding MAC address. Therefore, Mitchell ignores the request, and R1 decides to reply.

R1 replies with an ARP message called an ARP reply. Note that the ARP reply does not use a broadcast destination Ethernet address; instead, the destination address of the sender of the ARP broadcast is used. In this case, the destination is Hannah's Ethernet address (0200.1111.1111). As a result, the LAN switch does not flood the frame holding the ARP reply out all ports; instead, it forwards the frame only to Hannah. Figure 11-8 shows the ARP reply.