QUESTION NO: 9
Which two of the addresses below are available for host addresses on the subnet
192.168.15.19/28? (Select two answer choices)
A. 192.168.15.17
B. 192.168.15.14
C. 192.168.15.29
D. 192.168.15.16
E. 192.168.15.31
F. None of the above

Answer: A, C
Explanation:
The network uses a 28bit subnet (255.255.255.240). This means that 4 bits are used for
the networks and 4 bits for the hosts. This allows for 14 networks and 14 hosts (2n-2).
The last bit used to make 240 is the 4th bit (16) therefore the first network will be
192.168.15.16. The network will have 16 addresses (but remember that the first address is
the network address and the last address is the broadcast address). In other words, the
networks will be in increments of 16 beginning at 192.168.15.16/28. The IP address we
are given is 192.168.15.19. Therefore the other host addresses must also be on this
network. Valid IP addresses for hosts on this network are: 192.168.15.17-192.168.15.30.
Incorrect Answers:
B. This is not a valid address for this particular 28 bit subnet mask. The first network
address should be 192.168.15.16.
D. This is the network address.
E. This is the broadcast address for this particular subnet.


QUESTION NO: 10
You have a Class C network, and you need ten subnets. You wish to have as many
addresses available for hosts as possible. Which one of the following subnet masks
should you use?
A. 255.255.255.192
B. 255.255.255.224
C. 255.255.255.240
D. 255.255.255.248
E. None of the above

Answer: C
Explanation:
Using the 2n-2 formula, we will need to use 4 bits for subnetting, as this will provide for
24-2 = 14 subnets. The subnet mask for 4 bits is then 255.255.255.240.
Incorrect Answers:
A. This will give us only 2 bits for the network mask, which will provide only 2
networks.
B. This will give us 3 bits for the network mask, which will provide for only 6 networks.
D. This will use 5 bits for the network mask, providing 30 networks. However, it will
provide for only for 6 host addresses in each network, so C is a better choice.


QUESTION NO: 11
Which of the following is an example of a valid unicast host IP address?
A. 172.31.128.255./18
B. 255.255.255.255
C. 192.168.24.59/30
D. FFFF.FFFF.FFFF
E. 224.1.5.2
F. All of the above
Answer: A
Explanation
The address 172.32.128.255 /18 is 10101100.00100000.10|000000.11111111 in binary,
so this is indeed a valid host address.
Incorrect Answers:
B. This is the all 1's broadcast address.
C. Although at first glance this answer would appear to be a valid IP address, the /30
means the network mask is 255.255.255.252, and the 192.168.24.59 address is the
broadcast address for the 192.168.24.56/30 network.
D. This is the all 1's broadcast MAC address
E. This is a multicast IP address.
A groan grasps the peanut near the offending anthology.