N$8\mathrm{.}3.$ In Figure $1,$ Machine $x$ has established a VPN with Machine Y$,$ which is a VPN

server connected to the private network $10\mathrm{.}0.\frac{20\mathrm{.}0}{24}.$ With the VPN$,$ a user on

Machine X can now access machines on the $10\mathrm{.}0\mathrm{.}20\mathrm{.}0/24$ network. The user

runs the following command on Machine X: "telnet $10\mathrm{.}0\mathrm{.}20\mathrm{.}100".$ Figure $1$

shows the packet flow triggered by this command. Please answer the following

questions:

$($a$)$ What is the relationship between packets $1$ and $2?$

$($b$)$ What is the relationship between packets $3$ and $4?$

$($c$)$ What is the source IP and destination IP of packets $1,2,3,$ and $4?$

$($d$)$ What routing entries are needed on Machine $x?$

$($e$)$ What routing entries are needed on Machine Y$?$

$($f$)$ What routing entries are needed on Machine $10\mathrm{.}0\mathrm{.}20\mathrm{.}100?$

$($g$)$ If we break the VPN tunnel, what is going to happen to the telnet

connection? Is it going to be broken? After a few seconds, we reconnect the

VPN tunnel between $x$ and $Y,$ what is going to happen?

Figure $1$: Packet flow over VPN $($for Problem N$8\mathrm{.}3.)$

N$8\mathrm{.}4.$ A VPN allows Host U on a private network $192\mathrm{.}168\mathrm{.}60\mathrm{.}0/24$ to communicate

with Host V on another private network $192\mathrm{.}168\mathrm{.}80\mathrm{.}0/24.$ See Figure $2$ for the

VPN setup. Please describe the following:

Figure $2$: Figure for Problem N$8\mathrm{.}4.$

$($a$)$ What routing entries need to be added to Host U$,$ VPN Client, VPN server, and

Host V$?$ You don't need to write down the actual command, but you need to

describe those routing entries.

$($b$)$ When Host V receives a packet from Host U$,$ what is the source IP address of

the packet?

$($c$)$ When VPN server receives a packet from Host U to Host V$,$ via the VPN tunnel,

what is the source and destination IP addresses of the packet?

$($d$)$ After the VPN tunnel is set up$,$ when we ping Host V from Host U$,$ please

describe in details how the ICMP echo request packets get to Host V from Host

U$,$ and how the ICMP echo reply packets get back to Host U$.$