$(5$pts$)$ Suppose an ISP owns the block of addresses of the form $192\mathrm{.}168\mathrm{.}56\mathrm{.}128124.$ Suppose it wants to create four subnets from this block, with each block having the same number of IP addresses. What are the prefixes $($of form a$.$b$.$c$.$d$/$x$)$ for the four subnets? How many hosts can support in each subnet?

$(10$pts$)$ Consider the following figure. Suppose. Host A sends a datagram to Host F$.$ Give the source MAC addresses, destination MAC address, source IP address and destination IP address in the frame: a$)$ from A to the router R$1$; b$)$ from router R$1$ to F; c$)$ If A doesn't know F$\text{'}$s MAC address, what will A do$?$ d$)$ If C wants to send a datagram to F$,$ but C doesn't know F$\text{'}$s MAC address, what will C do$?$

Note: You do not need to provide specific IP$/$MAC addresses. Use placeholders like A$\text{'}$s IP$,$ A$\text{'}$s MAC, R$1\_$left's IP$/$MAC$,$ S$1\_$upper's IP$/$MAC otr

ANS:

a$)$ SrcMAC dest MAC: $$ Src IP $$ dest IP:

$$

b$)$ Src MAC: $$ dest MAC: $$ Src IP: $$ dest IP:

c$)$

d$)$