Module 4.6.3 IPv4 Addressing Quiz Answers

Network Addressing and Basic Troubleshooting – Module 4.6.3 IPv4 Addressing Quiz Answers

1. What subnet mask would provide an organization with 512 subnets, each capable of supporting at least 100 hosts, given the network prefix 10.25.0.0/16?

255.255.255.128
255.255.240.0
255.255.255.248
255.255.248.0

Explanation: The calculation should start with the IPv4 prefix 10.25.0.0/16. A subnet mask of 255.255.255.128 is required to create 512 subnets, with each subnet accommodating at least 100 hosts. The subnet mask 255.255.255.128 is equivalent to the notation of /25. The difference between /16 and /25 is 9 bits and the 9 bits will produce 512 subnets. A subnet mask notation /25 allows 7 bits for hosts and the 7 bits provide for 126 hosts

2. Which subnet mask would be used if exactly 4 host bits are available?

255.255.255.224
255.255.255.128
255.255.255.240
255.255.255.248

Explanation: The subnet mask of 255.255.255.224 has 5 host bits. The mask of 255.255.255.128 results in 7 host bits. The mask of 255.255.255.240 has 4 host bits. Finally, 255.255.255.248 represents 3 host bits.

3. Which network does a host with IP address 172.32.65.13 reside on if it is using a default subnet mask?

172.32.65.0
172.32.65.32
172.32.0.0
172.32.32.0

Explanation: In classful IPv4 addressing, a network with the first octet of 172 is a Class B network with the default subnet mask 255.255.0.0. Thus the network address is 172.32.0.0.

4. If a network device has a mask of /28, how many IP addresses are available for hosts on this network?

Explanation: A /28 mask is the same as 255.255.255.240. This leaves 4 host bits. With 4 host bits, 16 IP addresses are possible, but one address represents the subnet number and one address represents the broadcast address. 14 addresses can then be used to assign to network devices.

5. What does VLSM allow a network administrator to do?

utilize one subnet mask throughout an autonomous system
utilize multiple subnet masks in the same IP address space
utilize IGRP as the routing protocol in an entire autonomous system
utilize multiple routing protocols within an autonomous system

Explanation: VLSM allows subnets to be further subdivided into smaller subnets through use of multiple subnet masks within the same address space.

6. Which statement is true about variable length subnet masking?

Each subnet is the same size.
The size of each subnet may be different, depending on requirements.
Subnets may only be subnetted one additional time.
Bits are returned, rather than borrowed, to create additional subnets.

Explanation: In variable length subnet masking, bits are borrowed to create subnets. Additional bits may be borrowed to create additional subnets within the original subnets. This may continue until there are no bits available to borrow.

7. How many /30 subnets can be created from one /27 subnet?

Explanation: A /27 subnet contains 32 IP addresses, and a /30 subnet contains 4 IP addresses, so eight /30 subnets can be created from one /27 subnet.

8. A company has a network address of 192.168.30.128 with a subnet mask of 255.255.255.192. What additional subnetwork could be used to provide connectivity to 20 new hosts?

192.168.30.192 /27
192.168.30.160 /27
192.168.30.224 /29
192.168.30.0 /28

Explanation: The company originally started with a 192.168.30.128 /26. The current used address range includes 192.168.30.128 up to 192.168.30.191. The next available address is 192.168.30.192. When using the subnet mask 255.255.255.224, this provides up to 30 usable IP addresses and provides 192.168.30.192 as a possible network address.

9. A network administrator subnets the 192.168.10.0/24 network into subnets with /26 masks. How many equal-sized subnets are created?

Explanation: The normal mask for 192.168.10.0 is /24. A /26 mask indicates 2 bits have been borrowed for subnetting. With 2 bits, four subnets of equal size could be created.

10. Which subnet mask would be used if 5 host bits are available?

255.255.255.0
255.255.255.128
255.255.255.224
255.255.255.240

Explanation: The subnet mask of 255.255.255.0 has 8 host bits. The mask of 255.255.255.128 results in 7 host bits. The mask of 255.255.255.224 has 5 host bits. Finally, 255.255.255.240 represents 4 host bits.

11. How many valid host addresses are available on an IPv4 subnet that is configured with a /26 mask?

Explanation: When a /26 mask is used, 6 bits are used as host bits. With 6 bits, 64 addresses are possible, but one address is for the subnet number and one address is for a broadcast. This leaves 62 addresses that can be assigned to network devices.

12. How many usable IP addresses are available on the 192.168.1.0/27 network?

Explanation: A /27 mask is the same as 255.255.255.224. This leaves 5 host bits. With 5 host bits, 32 IP addresses are possible, but one address represents the subnet number and one address represents the broadcast address. Thus, 30 addresses can then be used to assign to network devices.