9. Addressing at the network and link layers, routing vs. switching Consider the network shown below. Each of the subnets A to D contains some hosts; subnet E connects routers RI and R2. Subnet B: Subnet C Subnet A: R2 R1 Subnet D: to public Internet via ISP a. Does the hosts in A need to know the MAC address of the RI's interface in subnet E in order to send an IP packet to the host in D? Explain your answer briefly Now suppose that router R2 above is replaced by an Ethernet switch S2, RI remains a router. Are the interfaces that previously were in subnets A B and E still in the same separate three IP subnets? Explain your answer a few sentences. b. c. In order to send an IP packet to the host in D, does the host in A ever nee to know the MAC address of the RI's left interface now, after R2 is replaced by S2? If so, how does it get the MAC address of RI's left interface? Explain briefly [Hint: Briefly describe how ARP protocol is used here.]