Consider the network in Fig. $7$ that contains four IPv$6$ subnets, connected by a mix of

IPv$6-$only routers, IPv$4-$only routers and dual$-$capable IPv$6/1$Pv$4$ routers.

Suppose that a host of subnet D wants to send an $113$v$6$ datagram to a host on subnet

B$.$

Assume that the forwarding between these two hosts goes along the path:

D $-->$ F $-->$ b $-->$a $-->$ c $-->$ B

Fig. $7$

Node A IPv$6$ Address: $225$C:$73$E$5$:$4$E$66$:$4$B$2$E:E$83$D:$992$B:A$489$:$35$C$4$

Node B IPv$6$ Address: $7$AAB:$488$A:$9463$:D$7$C$6$:F$199$:$929$D:B$18$B:F$589$

IPv$4$ Address: $200\mathrm{.}106\mathrm{.}85\mathrm{.}244$

Node C IPv$6$ Address: C$289$:EA$3$A:EB$59$:$3$E$73$:BE$56$:A$82$A:$576$D:$2$A$14$

IPv$4$ Address: $177\mathrm{.}241\mathrm{.}212\mathrm{.}13$

Node D IPv$6$ Address: A$429$:$772$D:$452$C:$18$F$7$:$8527$:$7$BEF:$5167$:$23$CF

Node E IPv$6$ Address: $8636$:A$49$F:C$582$:$894$C:$6499$:$8294$:$1712$:B$924$

IPv$4$ Address: $123\mathrm{.}15\mathrm{.}66\mathrm{.}4$

Node F IPv$6$ Address: $1$F$51$:F$141$:$9$A$2$F:$5$DAC:$3935$:$9961$:FA$7$D:E$453$

IPv$4$ Address: $86\mathrm{.}69\mathrm{.}18\mathrm{.}236$

Node a IPv$4$ Address: $220\mathrm{.}145\mathrm{.}255\mathrm{.}123$

Node b IPv$4$ Address: $119\mathrm{.}216\mathrm{.}244\mathrm{.}58$

Node c IPv$4$ Address: $47\mathrm{.}17\mathrm{.}208\mathrm{.}31$

Node d IPv$4$ Address: $28\mathrm{.}132\mathrm{.}237\mathrm{.}70$

Page $6$ of $7$

A$.$ Is the datagram being forwarded from D to Fan IPv$4$ or IPv$6$ datagram? $(1$ mark$)$

B$.$ What is the source address of this D to Fdatagram? $(1$ mark$)$

C$.$ What is the destination address of this D to F datagram? $(1$ mark$)$

D$.$ Is this D to F datagram encapsulating another datagram? Yes or No$.(1$ mark$)$

E$.$ Is the datagram being forwarded from F to b an IPv$4$ or IPv$6$ datagram?

What is its source and destination address of this F to b datagram? $(3$ marks$)$

F$.$ Is this F to b datagram encapsulating another datagram? Yes or No$.(1$ mark$)$

G$.$ What router is the 'tunnel entrance'? Give the router's letter. $(1$ mark$)$

H$.$ What router is the 'tunnel exit? Give the router's letter.