This 200-301 practice question tests your understanding of ip routing. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: a router selects the route with the longest prefix match when multiple routes match a destination IP address.. 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 packet is destined for 192.168.40.130. The routing table contains 192.168.40.0/24, 192.168.40.128/25, and 0.0.0.0/0. Which route is used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
192.168.40.128/25
The /25 route is used because it is the most specific matching prefix. In plain language, even though the /24 and the default route also technically match, the router prefers the entry that most precisely describes the destination range. Since 192.168.40.130 falls inside 192.168.40.128/25, that route wins under longest-prefix match.
This is a classic routing-table interpretation pattern. The router does not start with the default route when more specific routes exist, and it does not choose the /24 simply because it is familiar. Specificity comes first.
Key principle: A router selects the route with the longest prefix match when multiple routes match a destination IP address.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
192.168.40.0/24
Why it's wrong here
This is wrong because the /24 is less specific than the matching /25 route.
When this WOULD be correct
This option would be correct if the question specified that the destination IP was 192.168.40.200, which does not fall within the 192.168.40.128/25 range, making the broader 192.168.40.0/24 the best match.
✓
192.168.40.128/25
Why this is correct
This is correct because 192.168.40.130 falls within that more specific range.
Related concept
A router selects the route with the longest prefix match when multiple routes match a destination IP address.
✗
0.0.0.0/0
Why it's wrong here
This is wrong because the default route is used only when no more specific match exists.
When this WOULD be correct
If the question stated that the routing table only contained the default route 0.0.0.0/0 and no other specific routes for the destination IP, then this option would be correct as it would be the only available route for the packet.
✗
No route can be used because the entries overlap
Why it's wrong here
This is wrong because overlapping prefixes are normal and longest-prefix match resolves the choice.
When this WOULD be correct
In a different question setup where the routing table contains overlapping routes and the question explicitly states that the router cannot resolve which route to use due to ambiguity, this option would be correct, indicating that no definitive route can be selected.
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.
✓192.168.40.128/25Correct answer▾
Why this is correct
This is correct because 192.168.40.130 falls within that more specific range.
✗192.168.40.0/24Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because the more specific route 192.168.40.128/25 is actually the best match for the destination IP 192.168.40.130, which falls within that subnet range.
★ When this WOULD be the correct answer
This option would be correct if the question specified that the destination IP was 192.168.40.200, which does not fall within the 192.168.40.128/25 range, making the broader 192.168.40.0/24 the best match.
Why candidates choose this
Candidates may choose this option because it represents a broader subnet that includes the destination IP, leading to a common misconception that broader routes are always preferred over more specific ones.
✗0.0.0.0/0Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because the packet's destination IP address (192.168.40.130) matches the more specific route 192.168.40.128/25, which has a longer prefix length and thus takes precedence over the default route 0.0.0.0/0.
★ When this WOULD be the correct answer
If the question stated that the routing table only contained the default route 0.0.0.0/0 and no other specific routes for the destination IP, then this option would be correct as it would be the only available route for the packet.
Why candidates choose this
Candidates may choose this option due to the familiarity with the default route concept, mistakenly believing it serves all traffic when no specific routes are present, without considering the specific match of the destination IP.
✗No route can be used because the entries overlapWrong answer — click to see why▾
Why this is wrong here
This option is wrong because the routing table does not indicate that overlapping entries prevent routing; instead, the more specific route (192.168.40.128/25) is chosen for the packet destined for 192.168.40.130.
★ When this WOULD be the correct answer
In a different question setup where the routing table contains overlapping routes and the question explicitly states that the router cannot resolve which route to use due to ambiguity, this option would be correct, indicating that no definitive route can be selected.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of how overlapping routes are prioritized, mistakenly believing that overlaps inherently prevent routing rather than recognizing the specificity of the routes.
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
A common exam trap is assuming that the default route or a larger subnet like /24 will be chosen over a more specific subnet like /25. Candidates may incorrectly think the default route is preferred or that overlapping routes cause ambiguity. However, routers always use the longest prefix match rule, which means the route with the most specific subnet mask that includes the destination IP is selected. Misunderstanding subnet mask lengths or ignoring longest prefix match leads to wrong answers in routing questions.
Detailed technical explanation
How to think about this question
Routing tables use prefix matching to determine the best path for forwarding packets. Each route entry includes a network prefix and a subnet mask, defining a range of IP addresses. When a packet arrives, the router compares the destination IP against all prefixes in the routing table and selects the route with the longest matching prefix, also known as the most specific route. This process ensures that packets are forwarded along the most precise path available.
In this question, the destination IP 192.168.40.130 matches both 192.168.40.0/24 and 192.168.40.128/25 prefixes. The /25 subnet mask covers addresses from 192.168.40.128 to 192.168.40.255, which includes 192.168.40.130, while the /24 covers 192.168.40.0 to 192.168.40.255. Because /25 has a longer prefix length (more bits fixed), the router prefers this route over the /24. The default route 0.0.0.0/0 is only used if no more specific match exists.
A common exam trap is misunderstanding overlapping routes and default routes. Overlapping prefixes are normal in routing tables, and routers always choose the longest prefix match, not the first or the default route. Misreading the subnet mask length or assuming the default route is preferred can lead to incorrect answers. Practically, this behavior allows routers to implement hierarchical and summarized routing efficiently, forwarding packets to the most specific known network segment.
KKey Concepts to Remember
A router selects the route with the longest prefix match when multiple routes match a destination IP address.
Subnet masks define the specificity of a route; longer subnet masks represent more specific routes.
The default route 0.0.0.0/0 is used only when no other more specific route matches the destination IP.
Overlapping route entries in a routing table are normal and resolved by choosing the most specific prefix.
Routing decisions rely on prefix length before considering administrative distance or metrics.
A /25 subnet mask covers half of a /24 network, making it more specific for addresses within its range.
Routers do not prefer familiar or larger networks over more specific smaller subnets during route selection.
Longest prefix match routing ensures efficient and accurate packet forwarding in hierarchical IP networks.
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 router selects the route with the longest prefix match when multiple routes match a destination IP address.
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 router selects the route with the longest prefix match when multiple routes match a destination IP address., then practise related 200-301 questions on the same topic to reinforce the concept.
IP Routing — This question tests IP Routing — A router selects the route with the longest prefix match when multiple routes match a destination IP address..
What is the correct answer to this question?
The correct answer is: 192.168.40.128/25 — The /25 route is used because it is the most specific matching prefix. In plain language, even though the /24 and the default route also technically match, the router prefers the entry that most precisely describes the destination range. Since 192.168.40.130 falls inside 192.168.40.128/25, that route wins under longest-prefix match.
This is a classic routing-table interpretation pattern. The router does not start with the default route when more specific routes exist, and it does not choose the /24 simply because it is familiar. Specificity comes first.
What should I do if I get this 200-301 question wrong?
Review a router selects the route with the longest prefix match when multiple routes match a destination IP address., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
A router selects the route with the longest prefix match when multiple routes match a destination IP address.
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