100-150 Addressing and Subnet Formats Practice Test 2 — 15 Questions

Question 1

Refer to the exhibit. An administrator is reviewing the interface configuration. Which statement regarding these subnets is true?

Accepted Answer

The subnets are contiguous and correctly separated by 16 addresses each.. The exhibit shows three interfaces configured with /28 masks. A /28 mask provides 16 IP addresses per block. The first subnet is 172.16.5.0, the second is 172.16.5.16, and the third is 172.16.5.32. Because each interface is assigned the first host address of its respective block, the configuration is valid and follows classless inter-domain routing principles for non-overlapping subnets.

Answer

The subnets overlap, causing a routing conflict.

Answer

The configuration will fail because the IP addresses are not on the same network.

Answer

The mask /28 is invalid for these specific IP addresses.

Question 2

What is the decimal equivalent of the subnet mask 255.255.255.224?

Accepted Answer

/27. The subnet mask 255.255.255.224 corresponds to a /27 CIDR notation. The first three octets are all ones, and the last octet consists of three ones followed by five zeros (11100000), which equals 224 in decimal. Identifying CIDR masks from decimal notation is a core competency for Cisco technicians, as it is required for rapid network design and troubleshooting in real-world infrastructure environments.

Answer

/25

Answer

/26

Answer

/28

Question 3

Which THREE of the following are valid private IPv4 address ranges as defined in RFC 1918?

Accepted Answer

10.0.0.0/8. RFC 1918 defines specific address blocks reserved for private networks. These addresses are not routable on the public internet and are used internally to conserve public IPv4 address space. Technicians must be able to identify these ranges to configure NAT, DHCP, and internal routing policies accurately, as misusing public addresses in private ranges can lead to connectivity failures or security issues.

Answer

127.0.0.0/8

Answer

224.0.0.0/4

Question 4

A network engineer needs to allocate a subnet for a link connecting two routers. Which prefix provides the most efficient addressing for a point-to-point connection?

Accepted Answer

/30. A /30 mask leaves 2 host bits, yielding exactly 2 usable addresses — one for each router interface on the point-to-point link. That is the minimum needed for a functional link, so /30 is the most efficient allocation without wasting addresses.

Answer

/24

Answer

/28

Answer

/29

Question 5

Which component of an IPv4 address does the subnet mask identify?

Accepted Answer

The network and host portions of the address.. The subnet mask is a 32-bit value that, when ANDed with an IPv4 address, separates the network portion (bits set to 1 in the mask) from the host portion (bits set to 0). It tells the device which part of the address identifies the network and which part identifies the specific host on that network.

Answer

The MAC address of the destination device.

Answer

The default gateway for the host.

Answer

The TCP port number for the application.

Question 6

Which TWO of the following statements are true regarding IPv4 and IPv6 coexistence?

Accepted Answer

Dual-stack enables a device to run IPv4 and IPv6 protocol stacks simultaneously.. As the industry transitions from IPv4 to IPv6, coexistence mechanisms are required. Dual-stack allows devices to run both protocols simultaneously, while tunneling encapsulates IPv6 packets within IPv4 headers. These methods ensure that legacy systems can still communicate while modern IPv6-enabled infrastructure is deployed, which is a critical skill for network administrators managing hybrid, multi-protocol corporate environments during the long-term industry shift.

Answer

IPv6 addresses are directly compatible with IPv4 routing tables.

Answer

IPv4 is natively supported by all IPv6-only devices.

Answer

Broadcast traffic is still required for IPv6 address resolution.

Question 7

What is the broadcast address for the network 172.16.20.0/24?

Accepted Answer

172.16.20.255. In a /24 subnet (255.255.255.0), the network occupies the first three octets, and the last octet is available for hosts. The broadcast address is the very last address in the subnet range, where all host bits are set to one. For the 172.16.20.0 network, the last address is 172.16.20.255. This calculation is essential for identifying network boundaries and verifying traffic scope in Cisco configurations.

Answer

172.16.20.0

Answer

172.16.20.1

Answer

172.16.20.254

Question 8

Which of the following is the correct representation of the IPv6 address 2001:0DB8:0000:0000:0008:0800:200C:417A in compressed format?

Accepted Answer

2001:DB8::8:800:200C:417A. The correct compressed format is 2001:DB8::8:800:200C:417A. IPv6 compression rules (RFC 5952) allow leading zeros in each group to be omitted and a single contiguous sequence of all-zero groups to be replaced with '::'. Here, the two consecutive zero groups (0000:0000) are replaced by '::', and leading zeros in other groups are dropped (0DB8→DB8, 0008→8, 0800→800).

Answer

2001:DB8:0:0:8:800:200C:417A

Answer

2001:DB8::0000::8:800:200C:417A

Answer

2001:DB8:0000:0000:8:800:200C:417A

Question 9

Refer to the exhibit. What is the maximum number of usable host IP addresses available on this subnet?

Accepted Answer

62. The subnet is defined as a /26 mask. A /26 mask uses 6 bits for hosts (32 - 26 = 6). The formula for usable hosts is 2^6 - 2. This equals 64 minus 2, which results in 62 usable host addresses. Correctly calculating host capacity is vital for capacity planning and ensuring that subnets are sized appropriately to avoid IP address exhaustion within the enterprise network.

Answer

30

Answer

64

Answer

126

Question 10

Which of the following is a Class C IP address?

Accepted Answer

192.168.1.1. Class C IP addresses have a first octet in the range 192–223, and 192.168.1.1 falls within that range. Class C addresses use a default /24 subnet mask (255.255.255.0) and were historically assigned to small networks. This makes 192.168.1.1 the correct answer.

Answer

10.5.5.5

Answer

172.16.1.1

Answer

224.1.1.1

Question 11

Which TWO of the following statements regarding IPv4 address types are true?

Accepted Answer

Public IP addresses are globally routable across the internet.. Understanding the distinction between private, public, and special-use IPv4 addresses is critical for network security and traffic routing. Private addresses allow internal segmentation without internet visibility, while special addresses like the loopback range are essential for local service testing. Mastering these types prevents common errors like NAT misconfiguration or routing traffic into non-existent or internal-only address blocks across the network infrastructure.

Answer

Private IP addresses can be routed directly across the public internet.

Answer

The 127.0.0.0/8 range is used for private internal communication.

Answer

All IPv4 addresses are assigned automatically by the ISP.

Question 12

A network technician is tasked with dividing the 192.168.10.0/24 network into four equal-sized subnets to accommodate different departments. Which subnet mask should be applied to achieve this requirement, and how many usable host addresses will be available in each subnet?

Accepted Answer

255.255.255.192 with 62 hosts. To divide a /24 network into four equal subnets, you must borrow two bits from the host portion, changing the prefix from /24 to /26. A /26 prefix corresponds to a subnet mask of 255.255.255.192. Each resulting subnet contains 64 total addresses, but subtracting the network ID and broadcast address leaves 62 usable host addresses for devices.

Answer

255.255.255.128 with 126 hosts

Answer

255.255.255.224 with 30 hosts

Answer

255.255.255.240 with 14 hosts

Question 13

Which TWO statements correctly describe valid rules for compressing or representing IPv6 addresses?

Accepted Answer

Leading zeros in a quartet can be omitted.. Option A is correct because RFC 4291 permits omitting leading zeros within any 16-bit hexadecimal quartet, so '0db8' can be written as 'db8' and '0001' as '1'. Option B is correct because the '::' shorthand may be used only once in an address; it represents one or more consecutive groups of zeros, and using it twice would make the address ambiguous. Option C is wrong because only leading zeros may be dropped, not trailing zeros, since removing trailing zeros would change the value of the quartet. Option D is wrong because compression is optional, not mandatory, and a single '0000' quartet may be written as '0' or left uncompressed. Option E is wrong because IPv6 uses colons to separate quartets, while dots appear only in mixed IPv4-embedded notation such as '::ffff:192.168.0.1'.

Answer

Trailing zeros in a quartet can be omitted to save space.

Answer

A single quartet of '0000' must always be compressed to '::'.

Answer

IPv6 addresses use dots to separate quartets for better readability.

Question 14

A network administrator is configuring a point-to-point link between two routers and wants to use the most efficient subnet mask that allows for only two usable host addresses. However, the administrator is told to use a /28 mask instead for future expansion. How many usable host addresses are provided by a /28 mask?

Accepted Answer

14 usable host addresses. Determining the number of usable hosts requires identifying the total number of bits remaining for the host portion after the subnet mask is applied. For a /28 prefix, 4 bits are available for hosts, resulting in 16 total addresses. Subtracting the network ID and the broadcast address leaves 14 addresses that can be assigned to devices.

Answer

2 usable host addresses

Answer

6 usable host addresses

Answer

30 usable host addresses

Question 15

What is the directed broadcast address for the subnet in which the host 172.16.50.131/29 resides?

Accepted Answer

172.16.50.135. For 172.16.50.131/29, the subnet mask is 255.255.255.248, meaning each subnet has 8 addresses (2^3). The subnet containing .131 starts at .128 (network address) and ends at .135 (broadcast address). The directed broadcast address is the last address in the subnet, which is 172.16.50.135.

Answer

172.16.50.159

Answer

172.16.50.255

Answer

172.16.50.133