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. A key principle to apply: a subnet mask defines the network and host portions of an IP address, determining the local subnet boundaries for routing decisions.. 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.
A host with address 172.16.5.10/23 wants to determine whether 172.16.6.20 is on the same local network. What is the correct conclusion?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It is on a different network, so the host should use the default gateway
A /23 prefix covers two consecutive /24 ranges. In plain language, that means the network boundaries move in blocks of 2 in the third octet. The address 172.16.5.10/23 belongs to the 172.16.4.0/23 network, which covers 172.16.4.x and 172.16.5.x. The destination 172.16.6.20 belongs to a different /23 block, so it is not on the same local network.
This question checks whether you can think beyond default /24 boundaries and understand how a broader prefix changes the local network range. The host would therefore need to use its default gateway to reach 172.16.6.20, because that destination is off-subnet relative to the /23 in use.
Key principle: A subnet mask defines the network and host portions of an IP address, determining the local subnet boundaries for routing decisions.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
It is on the same local network because both addresses begin with 172.16.
Why it's wrong here
This is wrong because sharing the first two octets is not enough to determine the subnet relationship.
When this WOULD be correct
If the question stated that both addresses were part of a larger subnet, such as 172.16.0.0/16, then this option would be correct, as both addresses would indeed be on the same local network.
✗
It is on the same local network because /23 covers all addresses in 172.16.5.x and 172.16.6.x
Why it's wrong here
This is wrong because 172.16.5.10/23 belongs to the 172.16.4.0/23 block, not a block covering 5.x and 6.x.
When this WOULD be correct
If the question stated that the subnet mask was /22 instead of /23, then option B would be correct, as a /22 subnet would encompass both 172.16.5.x and 172.16.6.x addresses, allowing them to be on the same local network.
✓
It is on a different network, so the host should use the default gateway
Why this is correct
This is correct because 172.16.6.20 is not in the same /23 network as 172.16.5.10.
Related concept
A subnet mask defines the network and host portions of an IP address, determining the local subnet boundaries for routing decisions.
✗
It is on a different network, so ARP will resolve it across the router automatically
Why it's wrong here
This is wrong because ARP is a local-link mechanism and does not resolve remote hosts across routers.
When this WOULD be correct
If the question stated that both addresses were on the same local network but required ARP to resolve a device's MAC address for communication, then option D would be correct. For example, if both addresses were within the same subnet and the question asked about resolving a MAC address, D would apply.
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.
✓It is on a different network, so the host should use the default gatewayCorrect answer▾
Why this is correct
This is correct because 172.16.6.20 is not in the same /23 network as 172.16.5.10.
✗It is on the same local network because both addresses begin with 172.16.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because the addresses 172.16.5.10 and 172.16.6.20 belong to different subnets; 172.16.6.20 is in the 172.16.6.0/23 subnet, while 172.16.5.10 is in the 172.16.5.0/23 subnet.
★ When this WOULD be the correct answer
If the question stated that both addresses were part of a larger subnet, such as 172.16.0.0/16, then this option would be correct, as both addresses would indeed be on the same local network.
Why candidates choose this
Candidates may be drawn to this option because it highlights a common misconception that addresses starting with the same octets are always in the same network, ignoring the significance of the subnet mask.
✗It is on the same local network because /23 covers all addresses in 172.16.5.x and 172.16.6.xWrong answer — click to see why▾
Why this is wrong here
This option is incorrect because a /23 subnet mask allows for addresses in the range of 172.16.4.0 to 172.16.5.255, meaning 172.16.6.20 is outside this range and not on the same local network.
★ When this WOULD be the correct answer
If the question stated that the subnet mask was /22 instead of /23, then option B would be correct, as a /22 subnet would encompass both 172.16.5.x and 172.16.6.x addresses, allowing them to be on the same local network.
Why candidates choose this
Candidates may be tempted by this option because they recognize that both addresses share the same initial octets, leading them to mistakenly assume they are in the same subnet without considering the subnet mask.
✗It is on a different network, so ARP will resolve it across the router automaticallyWrong answer — click to see why▾
Why this is wrong here
Option D is incorrect because ARP (Address Resolution Protocol) operates within the same local network and cannot resolve addresses across routers. Since 172.16.6.20 is on a different network than 172.16.5.10, ARP cannot automatically resolve it.
★ When this WOULD be the correct answer
If the question stated that both addresses were on the same local network but required ARP to resolve a device's MAC address for communication, then option D would be correct. For example, if both addresses were within the same subnet and the question asked about resolving a MAC address, D would apply.
Why candidates choose this
Candidates might choose this option due to a misunderstanding of ARP's functionality, believing it can resolve addresses across different networks, which is a common misconception among those with limited networking knowledge.
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: answer the scenario, not the keyword
Don't assume addresses with the same initial octets are in the same subnet; always calculate based on the subnet mask.
Detailed technical explanation
How to think about this question
Subnetting is a fundamental concept in IP networking that divides a larger network into smaller, manageable segments called subnets. Each subnet is defined by a subnet mask or prefix length, which determines the network and host portions of an IP address. In this question, the /23 prefix means the first 23 bits of the IP address define the network portion, allowing the subnet to cover two consecutive /24 networks. For example, a /23 subnet starting at 172.16.4.0 includes all addresses from 172.16.4.0 to 172.16.5.255.
To determine if two IP addresses are on the same local network, a host applies its subnet mask to both addresses and compares the resulting network addresses. If they match, the addresses are on the same subnet; if not, they are on different networks. Here, 172.16.5.10/23 belongs to the 172.16.4.0/23 subnet, while 172.16.6.20 falls outside this range, indicating it is on a different subnet. Consequently, the host must forward traffic destined for 172.16.6.20 to its default gateway (router) for proper routing.
A common exam trap is assuming that IP addresses sharing the first two octets or even adjacent third octet values are always on the same subnet. This mistake ignores the subnet mask's role in defining network boundaries. In practical Cisco networking, understanding subnet boundaries is critical for correct routing and ARP behavior. ARP only resolves addresses on the local subnet; for remote subnets, the host relies on the default gateway to forward packets, emphasizing the importance of accurate subnet calculations.
KKey Concepts to Remember
A subnet mask defines the network and host portions of an IP address, determining the local subnet boundaries for routing decisions.
A /23 subnet mask covers two consecutive /24 networks, effectively doubling the size of the local subnet compared to a /24 mask.
To verify if two IP addresses are on the same subnet, a host applies its subnet mask to both addresses and compares the resulting network addresses.
If the network addresses differ after masking, the destination is off-subnet, requiring the host to forward packets to its default gateway router.
ARP operates only within the local subnet and cannot resolve IP addresses that belong to different subnets across routers.
Hosts must use the default gateway to communicate with devices outside their local subnet, ensuring proper routing of traffic.
Assuming IP addresses are local based solely on matching initial octets without considering the subnet mask leads to incorrect routing behavior.
Cisco networking exams test understanding of subnetting beyond default classful boundaries, emphasizing precise subnet mask application.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
A subnet mask defines the network and host portions of an IP address, determining the local subnet boundaries for routing decisions.
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 a subnet mask defines the network and host portions of an IP address, determining the local subnet boundaries for routing decisions., then practise related 200-301 questions on the same topic to reinforce the concept.
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — A subnet mask defines the network and host portions of an IP address, determining the local subnet boundaries for routing decisions..
What is the correct answer to this question?
The correct answer is: It is on a different network, so the host should use the default gateway — A /23 prefix covers two consecutive /24 ranges. In plain language, that means the network boundaries move in blocks of 2 in the third octet. The address 172.16.5.10/23 belongs to the 172.16.4.0/23 network, which covers 172.16.4.x and 172.16.5.x. The destination 172.16.6.20 belongs to a different /23 block, so it is not on the same local network.
This question checks whether you can think beyond default /24 boundaries and understand how a broader prefix changes the local network range. The host would therefore need to use its default gateway to reach 172.16.6.20, because that destination is off-subnet relative to the /23 in use.
What should I do if I get this 200-301 question wrong?
Review a subnet mask defines the network and host portions of an IP address, determining the local subnet boundaries for routing decisions., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
A subnet mask defines the network and host portions of an IP address, determining the local subnet boundaries for routing decisions.
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