Question $2$:

What is the first address of a block of classless addresses if one of the addresses is $120\mathrm{.}23\mathrm{.}7\mathrm{.}17\frac{?}{17}?$

A$.120\mathrm{.}23\mathrm{.}7\mathrm{.}0$

$120\mathrm{.}23\mathrm{.}0\mathrm{.}0$

$120\mathrm{.}0\mathrm{.}0\mathrm{.}0$

$$ none of the above

Datagram packet switching is used on the Internet because it is

Reliable

Robust

Usable

$$ More suitable for routers

Which field of the IPv$4$ header never changes from router to router

$$ Checksum

$$ TTL

$$ Destination address

$$ Fragmentation Offset