Consider Figure 5.38. Now we replace the router between subnets I and 2 with a switch S l, and label the router between subnets 2 and 3 as R l.
a. Consider sending an IP datagram from Host E to Host F. Will Host E ask router R l to help forward the datagram? Why? In the Ethernet frame containing the IP datagram, what are the source and destination IP and MAC addresses?
b. Suppose E would like to send an IP datagram to B, and assume that E's ARP cache does not contain B's MAC address. Will B perform an ARP query to find B's MAC address? Why? In the Ethernet frame (containing the IP datagram destined to B) that is delivered to router R 1, what are the source and destination IP and MAC addresses'?
c. Suppose Host A would like to send an IP datagram to Host B, and neither A's ARP cache contains 8's MAC address nor does B's ARPcache contain A's MAC address. Further suppose that the switch S l 's forwarding table contains entries for Host B and router R l only. Thus, A will broadcast an ARP request message. What actions will switch S I perform once it receives the ARP request message? Will router R I also receive this ARP request message? If so. will R I forward the message to Subnet 3? Once Host B receives this ARP request message, it will send back to Host A an ARP response message. But will it send an ARP query message to ask for A's MAC address? Why? What will switch S I do once it receives an ARP response message from Host B?