$1.$ A network requires $150000$ addresses. Which old class IPv$4$ address format or class is suitable? I.e$.,$ one that results in the least number of wasted IPv$4$ addresses.

$2.$ Find the network identity of the following IPv$4$ addresses

a$.20\mathrm{.}1\mathrm{.}2\mathrm{.}3/21$

b$.130\mathrm{.}2\mathrm{.}1\mathrm{.}160/18$

$3.$ Write down following masks in slash notation $(/$n$)$

a$.255\mathrm{.}255\mathrm{.}255\mathrm{.}0,($b$)255\mathrm{.}0\mathrm{.}0\mathrm{.}0,($c$)255\mathrm{.}255\mathrm{.}224\mathrm{.}0,$ and $($d$)255\mathrm{.}255\mathrm{.}240\mathrm{.}0$

$4.$ Consider the address block $172\mathrm{.}6\mathrm{.}32\mathrm{.}0/22.$ A network operator decides to create a new address block

$172\mathrm{.}6\mathrm{.}32\mathrm{.}0/25.$ How many subnets did he$/$she create?

$5.$ What is the difference between the port number used by a client to identify its connection versus

the one used at a server?

$6.$ A NAT uses a port number to identify connection. In which header can it find this information?

$7.$ What information can a NAT use to distinguish connections from private IPv$4$ hosts?

$8.$ Why does a NAT act as a firewall?

$9.$ A private host is using port number $9999.$ Can a NAT also use port $9999$ to identify the host? Discuss

a scenario in which the NAT is unable to use port $9999.$

$10.$ How does the use of a NAT reduce the need to adopt IPv$6?$