Subnet Masks

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
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
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
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
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

6. Working at the help desk, you receive 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
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.
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 addresses into network, subnet, and host parts
d. Ignores Class A, B, and C network rules
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