Analyzing Subnet Masks

Question 1

Which of the following answers lists the prefix (CIDR) format equivalent of 255.255.254.0?

a. /19
b. /20
c. /23
d. /24
e. /25

Answer 1

c. /23

Question 2

Which of the following answers lists the prefix (CIDR) format equivalent of 255.255.255.240?

a. /26
b. /28
c. /27
d. /30
e. /29

Answer 2

b. /28

Question 3

Which of the following answers lists the dotted-decimal notation (DDN) equivalent of /24?

a. 255.255.240.0
b. 255.255.252.0
c. 255.255.255.0
d. 255.255.255.192
e. 255.255.255.240

Answer 3

c. 255.255.255.0

Question 4

Which of the following answers lists the dotted-decimal notation (DDN) equivalent of /30?

a. 255.255.255.192
b. 255.255.255.252
c. 255.255.255.240
d. 255.255.254.0
e. 255.255.255.0

Answer 4

b. 255.255.255.252

Question 5

Working at the help desk, you receive a call and learn a user’s PC IP address and mask (10.55.66.77, mask 255.255.255.0). When thinking about this using classful logic, you determine the number of network (N), subnet (S), and host (H) bits. Which of the following is true in this case?

a. N = 12
b. S = 12
c. H = 8
d. S = 8
e. N = 24

Answer 5

c. H = 8

Question 6

Working at the help desk, you recieve a call and learn a user’s PC IP address and mask (192.168.9.1/27). When thinking about this using classful logic, you determine the number of network (N), subnet (S), and host (H) bits. Which of the following is true in this case?

a. N = 24
b. S = 24
c. H = 8
d. H = 7

Answer 6

a. N = 24

Question 7

An engineer is thinking about the following IP address and mask using classless IP addressing logic: 10.55.66.77, 255.255.255.0. Which of the following statements are true when using classless addressing logic? (choose two)

a. The network part’s size is 8 bits
b. The prefix length is 24 bits
c. The prefix length is 16 bits
d. The host part’s size is 8 bits

Answer 7

b. The prefix length is 24 bits

d. The host part’s size is 8 bits

Question 8

Which of the following statements is true about classless IP addressing concepts?

a. Uses a 128-bit IP address
b. Applies only for Class A and B networks
c. Separates IP address into network, subnet, and host parts
d. Ignores Class A, B, and C network rules

Answer 8

d. Ignores Class A, B, and C network rules

Question 9

Which of the following masks, when used as the only mask within a Class B network, would supply enough subnet bits to support 100 subnets? (Choose two)

a. /24
b. 255.255.255.252
c. /20
d. 255.255.252.0

Answer 9

a. /24

b. 255.255.255.252

Question 10

What are the rules of the binary subnet mask?

Answer 10

• The value must not interleave 1s and 0s
• If 1s exist, they on the left
• if 0s exist, they on the right

Question 11

This format takes advantage of the rule that the subnet mask starts with some number of 1s, and then the rest of the digits are 0s.

Answer 11

Prefix format

Question 12

The concept that an IPv4 address has two parts-the prefix part plus the host part-as defined by the mask, with no consideration of the class (A,B, or C).

Answer 12

Classless addressing

Question 13

The concept that an IPv4 address has three parts-network, subnet, and host-as defined by the mask and Class A, B, and C rules

Answer 13

Classful addressing