CCNA IP Routing Practice Question
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?
⚠ Common exam trap
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.
Answer choices
Why each option matters
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.
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.
- ✗
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
Overlapping routes are permitted in a routing table, and the router selects the most specific match (longest prefix length) for 192.168.40.130, which is 192.168.40.128/25 (a /25 covers 192.168.40.128–.255). Overlap alone does not invalidate a route; the router uses the longest prefix match algorithm. This option is tempting because overlapping prefixes can cause confusion in static route configuration or redistribution, and in a scenario where overlapping routes were injected from different routing protocols without administrative-distance control, a routing loop or suboptimal path could occur—but here the router simply picks the most specific entry.
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?”
Visual reference
Quick reference
IPv4 Address Class Summary
| Class | First Octet Range | Default Mask | Networks | Hosts per Network |
|---|---|---|---|---|
| A | 1–126 | /8 (255.0.0.0) | 126 | 16,777,214 |
| B | 128–191 | /16 (255.255.0.0) | 16,384 | 65,534 |
| C | 192–223 | /24 (255.255.255.0) | 2,097,152 | 254 |
| D | 224–239 | N/A | Multicast groups | — |
| E | 240–255 | N/A | Reserved / experimental | — |
127.x.x.x is reserved for loopback. Modern networks use CIDR (classless) rather than classful addressing.
Go deeper
Related to this question
Learn chapter
OSPFv3 Single-Area Configuration for IPv6
Key term
Route
A route is a path that data takes through a network from one device or network to another, determined by routing protocols and configured rules.
Key term
Router
A router is a networking device that connects different networks together and directs data traffic between them by choosing the best path for data to travel.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.