A national retail chain needs to design an IP addressing scheme to support a nationwide
network. The company needs a minimum of 300 sub-networks and a maximum of 50 host
addresses per subnet. Working with only one Class B address, which of the following subnet
masks will support an appropriate addressing scheme? (Choose two.)

A.
255.255.255.0

B.
255.255.255.128

C.
255.255.252.0

D.
255.255.255.224

E.
255.255.255.192

F.
255.255.248.0

Explanation:
Subnetting is used to break the network into smaller more efficient subnets to prevent
excessive rates of Ethernet packet collision in a large network. Such subnets can be
arranged hierarchically, with the organization’s network address space (see also
Autonomous System) partitioned into a tree-like structure. Routers are used to manage
traffic and constitute borders between subnets.
A routing prefix is the sequence of leading bits of an IP address that precede the portion of
the address used as host identifier. In IPv4 networks, the routing prefix is often expressed as
a “subnet mask”, which is a bit mask covering the number of bits used in the prefix. An IPv4
subnet mask is frequently expressed in quad-dotted decimal representation, e.g.,
255.255.255.0 is the subnet mask for the 192.168.1.0 network with a 24-bit routing prefix
(192.168.1.0/24).