CCNA Network Infrastructure and Connectivity Practice Question
This 200-301 practice question tests your understanding of network infrastructure and connectivity. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which statement best explains why a host with a correct IP address but incorrect subnet mask may still fail to communicate properly?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Because the host may misidentify local versus remote destinations and choose the wrong forwarding behavior.
An incorrect subnet mask breaks the host's ability to distinguish which destinations are local and which are remote. In practical terms, the host may try to ARP for remote destinations that should have gone to the gateway, or it may send local traffic toward the router unnecessarily. That makes normal forwarding decisions unreliable even if the IP address itself looks valid.
This is why correct addressing includes both the address and the mask, not just one of them.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Because the host may misidentify local versus remote destinations and choose the wrong forwarding behavior.
Why this is correct
This is correct because the subnet mask drives local-versus-remote decisions.
Clue confirmation
The clue word "best" in the question point toward this answer.
Because the subnet mask is used only by switches, not hosts.
Why it's wrong here
This is wrong because hosts absolutely use the subnet mask.
When this WOULD be correct
In a question that asks about the role of subnet masks in network devices, if it specifies that the focus is solely on switches and their operation, then this option could be correct. For example, if the question states that subnet masks are only relevant in the context of switch routing decisions, this would validate option B.
✗
Because the mask automatically provides DNS name resolution.
Why it's wrong here
This is wrong because DNS and subnet masks solve different problems.
When this WOULD be correct
In a different question setup, if the question asked about the functions of various network components, including DNS, and how they interact with IP addressing, option C could be correct if it stated that the subnet mask assists in name resolution by defining the network boundaries for DNS queries.
✗
Because the subnet mask replaces the need for a default gateway.
Why it's wrong here
This is wrong because the mask and gateway serve different purposes.
When this WOULD be correct
In a question asking about network configurations where a subnet mask is described as a substitute for routing mechanisms or default gateways, option D could be correct. For example, if the question states that a device is configured to operate without a default gateway due to a specific network design, then this option would be valid.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Because the host may misidentify local versus remote destinations and choose the wrong forwarding behavior.Correct answer▾
Why this is correct
This is correct because the subnet mask drives local-versus-remote decisions.
✗Because the subnet mask is used only by switches, not hosts.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because subnet masks are used by hosts to determine the network portion of an IP address, not exclusively by switches. Hosts rely on subnet masks to identify local networks for communication.
★ When this WOULD be the correct answer
In a question that asks about the role of subnet masks in network devices, if it specifies that the focus is solely on switches and their operation, then this option could be correct. For example, if the question states that subnet masks are only relevant in the context of switch routing decisions, this would validate option B.
Why candidates choose this
Candidates may find this option tempting due to a common misconception that subnet masks are primarily associated with switch functionality, leading them to overlook the critical role they play in host communication.
✗Because the mask automatically provides DNS name resolution.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because the subnet mask does not provide DNS name resolution; it is used to determine the network portion of an IP address. DNS resolution is handled by DNS servers, not the subnet mask.
★ When this WOULD be the correct answer
In a different question setup, if the question asked about the functions of various network components, including DNS, and how they interact with IP addressing, option C could be correct if it stated that the subnet mask assists in name resolution by defining the network boundaries for DNS queries.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of how IP addressing and DNS interact, mistakenly believing that the subnet mask plays a role in resolving domain names rather than just defining network segments.
✗Because the subnet mask replaces the need for a default gateway.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because the subnet mask is crucial for hosts to determine their local network and does not replace the need for a default gateway, which is essential for routing traffic outside the local subnet.
★ When this WOULD be the correct answer
In a question asking about network configurations where a subnet mask is described as a substitute for routing mechanisms or default gateways, option D could be correct. For example, if the question states that a device is configured to operate without a default gateway due to a specific network design, then this option would be valid.
Why candidates choose this
Candidates may find this option tempting because they might confuse the roles of subnet masks and default gateways, leading them to believe that a subnet mask could eliminate the need for a default gateway in certain scenarios.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 200-301 subnetting questions on CIDR, address ranges, and subnet selection.
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Because the host may misidentify local versus remote destinations and choose the wrong forwarding behavior. — An incorrect subnet mask breaks the host's ability to distinguish which destinations are local and which are remote. In practical terms, the host may try to ARP for remote destinations that should have gone to the gateway, or it may send local traffic toward the router unnecessarily. That makes normal forwarding decisions unreliable even if the IP address itself looks valid.
This is why correct addressing includes both the address and the mask, not just one of them.
What should I do if I get this 200-301 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 200-301 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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