Addressing and Subnetting (Answers)
1. You have a network ID of 172.16.0.0 and you need to divide it into multiple subnets. You
need 600 host Ids for each subnet. Which subnet mask should you assign that will allow for
growth?
A. 255.255.224.0
C. 255.255.248.0
B. 255.255.240.0
D. 255.255.252.0
2. You have a network ID of 172.16.0.0 with eight subnets. You need to allow for the largest possible
number of host IDs per subnet. Which subnet mask should you assign?
A. 255.255.224.0
C. 255.255.248.0
B. 255.255.240.0
D. 255.255.252.0
3. You have a network ID of 192.168.55.0 and you need to divide it into multiple subnets. You
need 25 host IDs for each subnet, with the largest amount of subnets available. Which subnet
mask should you assign?
A. 255.255.255.192
C. 255.255.255.240
B. 255.255.255.224
D. 255.255.255.248
4. You have a Class A network address with 60 subnets. You need to add 40 new subnets in the
next two years, but still allow for the largest possible number of host IDs per subnet. Which
subnet mask should you assign ?
A. 255.240.0.0
C. 255.252.0.0
B. 255.248.0.0
D. 255.254.0.0
5. You have a Class C network address of 192.168.19.0 with four subnets. You need the largest
possible number of host IDs per subnet. Which subnet mask should you assign?
A. 255.255.255.192
C. 255.255.255.240
B. 255.255.255.224
D. 255.255.255.248
6. You have a Class B network address divided into 30 subnets. You will add 25 new subnets
within the next two years. You need 600 host IDs for each subnet. Which subnet mask should
you assign?
A. 255.192.0.0
C. 255.255.248.0
B. 255.254.0.0
D. 255.255.252.0
7. You have a network ID of 192.168.1.0 and you need to divide it into nine subnets. You need
to provide for the largest possible number of host IDs per subnet. Which subnet mask should
you assign?
A. 255.255.255.192
C. 255.255.255.240
B. 255.255.255.224
D. 255.255.255.248
8. You have a Class C network address divided into three subnets. You will need to add two
subnets in the next two years. Each subnet will have 25 hosts. Which subnet mask should you
assign?
A. 255.255.255.0
C. 255.255.255.224
B. 255.255.255.192
D. 255.255.255.248
9. You have a Class C network address of 192.168.88.0 and you need the largest possible
number of subnets, with up to 12 hosts per subnet. What is the subnet mask?
A. 255.255.255.192
C. 255.255.255.240
B. 255.255.255.224
D. 255.255.255.248
10. You need to come up with a TCP/IP addressing scheme for your company. How many
network Ids must you allow for when you define the subnet mask for the network?
A. One for each subnet
B. One for each host ID
C. One for each router interface
D. One for each WAN connection
E. One for each network adapter installed on each host
Each host on the network must have a unique IP address. However, you are required to have only
one network ID per network. Each host must share a common network ID, as well as connections
between networks, which are the WAN connections.
11. You need to come up with a TCP/IP addressing scheme for your company. Which two
factors must you consider when you define the subnet mask for the network?
A.
B.
C.
D.
E.
The number of subnets on the network
The number of host Ids on each subnet
The volume of network traffic on each subnet
The location of DNS servers
The location of default gateways
12. You need to come up with a TCP/IP addressing scheme for your company. How many host
IDs must you allow for when you define the subnet mask for the network?
A. One for each subnet
C. One for each WAN connection
B. One for each router interface
D. One for each network adapter installed
on each host
13. You have an IP address of 172.16.3.57 with an 11-bit subnet mask. What are your valid
hosts?
A. 172.16.3.32 to 172.16.3.62
C. 172.16.3.34 to 172.16.3.62
B. 172.16.3.33 to 172.16.3.62
D. 172.16.3.57 to 172.16.3.62
14. You have a subnet mask of 255.255.255.248. How many subnets and hosts do you have?
A. 2,097,150 subnets w/ 8 hosts
C. 30 subnets w/ 14 hosts
B. 8190 subnets w/ 6 hosts
D. 6 subnets w/ 30 hosts
15. You have an IP address of 172.16.4.58 with a 12-bit subnet mask. What are your valid hosts?
A. 172.16.4.48 to 172.16.4.63
C. 172.16.4.49 to 172.16.4.62
B. 172.16.4.49 to 172.16.4.63
D. 172.16.4.55 to 172.16.4.62
16. You have an IP address of 172.16.13.5 with a 255.255.255.128 subnet mask. What is your
class of address, subnet address, and braodcast address?
Class B, Subnet 13, Broadcast address 255.255.255.127.
Valid range for hosts is 172.16.13.1 - 172.16.13.126
17. If you have a 22-bit subnet mask, how many subnets and how many hosts do you have?
A. 8190 subnet
w/ 4096 hosts
C. 2,096,138 subnets w/ 6 hosts
B. 4,194,302 subnets w/ 2 hosts
D. 16,384 subnets w/ 2046 hosts
18. If you have a 19-bit subnet mask, how many subnets and how many hosts do you have?
A. 8190 subnets
w/ 126 hosts
C. 524,286 subnets w/ 30 hosts
B. 524,288 subnets w/ 32 hosts
D. 65,234 subnets w/ 62 hosts
19. If you have a Class B network with a 10-bit subnet mask, how many subnets and how many
hosts do you have?
A. 1022 subnets w/ 62 hosts
C. 8190 subnets w/ 254 hosts
B. 62 subnets w/ 8190 hosts
D. 254 subnets w/ 126 hosts
20. If you have a Class C network with a 6-bit subnet mask, how many subnets and how many
hosts do you have?
A. 254 subnets w/ 30 hosts
C. 62 subnets w/ 2 hosts
B. 64 subnets w/ 8 hosts
D. 30 subnets w/ 2 hosts
21. What is the network address for 96.2.3.16?
A. 96.2.0.0
C. 96.0.0.0
B. 96.2.3.0
D. Can’t tell
22. What class of address is 190.233.27.13?
A. Class A
C. Class C
B. Class B
D. Class D
23. How many bits are in the default subnet mask for the address 219.25.23.56?
A. 8
C. 24
B. 16
D. 32
24. How many hosts are supported by a Class C network address, without subnetting ?
A. 254
B. 65,000
C. 255
D. 16,000
There are 8 bits (256 addresses) available for hosts in a Class C network, but host numbers 0 and
255 are not allowed.
25. What is the default mask for a Class B network?
A. 255.0.0.0
C. 255.255.0.0
B. 255.255.255.0
D. 255.225.0.0
26. Approximately how many unique networks are possible with a Class B address?
A. 254
B. 16K
C. 65K
D. 2M
A Class B address allocates 16 bits (65K) for the network address, but the address class
predetermines three of these bits. In other words, 128 through 191 are the only possible values
for the first octet.
27. What is the decimal value of the decimal number 11001011?
A. 203
C. 207
128+64+8+2+1 = 203
B. 171
D. 193
28. What is the binary value of the decimal number 219 ?
A. 11101011
C. 11101011
219-128-64-16-8-2-1 = 0
B. 01011101
D. 11011011
29. Subnet bits are added to _________ to segment the network into subnets
A. The network address
C. The host address
B. The default subnet mask
D. The subnet ID
30. If eight bits were allocated to subnetting with a Class B address, how many subnets would be
possible?
A. 62
C. 254
B. 256
D. 16K
31. Given the subnet mask 255.255.255.240 on a Class A address, how many bits are allocated to
subnetting?
A. 4
C. 9
B. 5
D. 12
32. If the subnet mask for the network 150.25.0.0 is 255.255.224.0, which of these is a valid host
address?
A. 150.25.0.27
C. 150.25.40.24
B. 150.25.30.23
D.150.25.224.30
33. What is the first subnet ID for the network 25.0.0.0 with a subnet mask of 255.192.0.0?
A. 25.192.0.0
C. 25.128.0.0
B. 25.64.0.0
D. 25.192.64.0
34. What is the maximum number of subnet bits possible with a Clas C address?
A. 6
B. 8
C. 14
D. 12
Since there are only eight bits in the host portion of a Class C address, we must leave at least two
bits for hosts, which would only provide two legal bit combinations, 01 and 10 for host
addresses.
35. Given a subnet mask of 255.255.240.0?
A. 150.150.37.2
B. 150.150.16.2
C. 150.150.8.12
D. 150.150.49.15
The addresses given are Class B, which means the subnet mask includes four bits for subnetting.
The lowest-order bit is 16, which means the first legal subnet is 150.150.16.0
36. How many hosts per subnet are possible with a Class B address, if five bits are added to the
default mask for subnetting?
A. 510
C. 1022
B. 512
D. 2046
37. If you were issued a Class C address, and needed to divide the network into seven subnets,
with up to 15 hosts in each subnet, what subnet mask would you use?
A. 255.255.255.224
B. 255.255.224
C. 255.255.255.240
D. None of the above
This is an impossible situation. To achieve seven subnets we would need to use four subnet bits.
This is because even though three bits would give us eight possible addreses, all zeros and all
ones are not permitted. If we use four bits for subnetting, this only leaves four bits for host
addresses, which will only accommodate 14 hosts for subnets.
38. Given an IP address of 125.3.54.56, without any subnetting, what is the network number?
A. 125.0.0.0
C. 125.3.54.0
B. 125.3.0.0
D. 125.3.54.32
39. The network 154.27.0.0 can support how many hosts, if not subnetted?
A. 254
C. 65,533
B. 1024
D. 16,777,206
40. Which of the following is a legitimate IP host address?
A. 1.255.255.2
B. 127.2.3.5
C. 225.23.200.9
D. 192.240.150.255
Answer B uses the 127 network which is reserved for loopback testing.
41. What is the significance of the address 3.255.255.255?
A. It is a host number
B. It is a local broadcast
C. It is a directed broadcast
D. It is an illegal address
It is a directed broadcast to network 3.0.0.0 A local broadcast would have all ones, for example
255.255.255.255
42. A bit pattern of 1111 leading the first octet of an address would imply what network class?
A. Class B
C. Class D
B. Class C
D. Class E
43. What is the binary equivalent of the decimal 234?
A. 11101010
C. 10111110
B. 10111010
D. 10101111
44. What is the decimal equivalent of 01011100 ?
A. 96
C. 84
B. 92
D. 154
45. The purpose of subnetting is to:
A.
B.
C.
D.
Segment and organize a single network at the network layer
Divide a network into several different domains
Allow bridging between network segments
Isolate groups of hosts so they can’t communicate
46. Subnetting is achieved by the following actions:
A.
B.
C.
D.
Subtracting bits from the default subnet mask
Subtracting bits from the network address
Adding bits to the host address
Adding bits to the default subnet mask
47. If we add four bits to the default mask, what is the number of subnets we can define?
A. 16
C. 14
B. 15
D. 12
48. What is the maximum number of subnet bits we can add to a default mask?
A. 8 bits
C. 30 bits
B. 16 bits
D. Depends on the address class
49. What is the subnet mask for a Class B address that has three subnet bits added?
A. 255.255.240.0
C. 255.224.0.0
B. 255.255.224.0
D. 255.255.248.0
50. What is the subnet mask if we add 12 bits to the default Class A subnet mask?
A. 255.255.255.240
C. 255.240.0.0
B. 255.255.240.0
D. 255.255.224.0
51. Given a subnet mask of 255.255.255.0 with a Class B address, how many subnets are
available?
A. None
C. 16K
B. 254
D. 65K
52. What happens to the number of hosts per subnet each time we add an additional subnet bit?
A. Hosts are not affected
B. Available hosts are decreased by two
C. Hosts per subnet is approximately ½ D.Hosts per subnet is doubled
Each time we take a bit from the host portion of the IP address for use in subnetting, we cut the
available number of hosts roughly in half. For example, eight host bits gives 254 hosts (256-2).
Reducing this to seven host bits would result in 126 valid hosts (128-2). In each case we are
excluding the all-zeros and the all-ones bit combinations.
53. In order to accommodate seven subnets, how many subnet bits are required?
A. 3
C. 6
B. 4
D. 7
54. If we included six subnet bits in the subnet mask for a Class C address, how many hosts
would each network suport?
A. 254
C. 4
B. 30
D. 2
55. What class of address is needed to provide 2,000 subnets, each with 5,000 users ?
A. Class A
C. Class C
B. Class B
D. Class D
56. Given a subnet address of 140.125.8.0 with a subnet mask of 255.255.252.0, what is the
subnet address of the next higher subnet?
A. 140.125.16.0
C. 140.125.32.0
B. 140.125.17.0
D. 140.125.12.0
57. Given a sunet address of 5.32.0.0 and a subnet mask of 255.224.0.0, what is the highest
allowed host address on this subnet?
A. 5.32.255.254
C. 5.63.255.254
B. 5.32.254.254
D. 5.63.255.255
58. If we saw the following subnet addresses, what would be the subnet mask associated with
these subnets? 140.120.4.0
140.120.8.0
140.120.12.0
140.120.16.0
A. 255.255.252.0
B. 255.252.0.0
C. 255.255.248.0
D. 255.255.4.0
The pattern of subnet addresses reveals that the interval is 4 and the lowest subnet has a value of
4. In order to use contiguous high-order bits in our subnet mask, this would mean that we have
six bits reserved for subnetting. Since we are dealing with a Class B address, we add these six
bits to the default subnet mask of 255.255.0.0
59. Given the network 2.0.0.0 with a subnet mask of 255.255.224.0 which of these is not a valid
ID for this network?
A. 2.255.192.0
C. 2.0.16.0
B. 2.0.224.0
D. 2.254.192.0
60. What is the subnet mask for an address of 175.25.0.0/24?
A. 255.255.0.0
C. Depends on address class
B. 255.255.255.0
D. 255.255.240.0