CCNA IP Routing Practice Question
A router learns 10.0.0.0/8 from OSPF and 10.10.0.0/16 from a static route. Which route is used for traffic to 10.10.20.1?
⚠ Common exam trap
A frequent mistake is to assume that the OSPF route will be used simply because it is dynamically learned, or because it covers a larger network range. Candidates often overlook that the router applies longest-prefix match first, which means the more specific static route with a /16 mask takes precedence over the broader /8 OSPF route. This misunderstanding leads to incorrect answers, as the router does not ignore static routes in favor of OSPF when the static route is more specific. Remember, overlapping routes are common, and the router always chooses the route with the most specific subnet mask matching the destination.
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
✓
The static 10.10.0.0/16 route
The static /16 route is used because it is more specific than the OSPF /8 route. In practical terms, even though both routes match the destination, the router chooses the one that narrows the destination range more precisely. Since 10.10.20.1 belongs to 10.10.0.0/16, that entry wins. This question reinforces that longest-prefix match comes first. The broader OSPF route still matters for other destinations inside 10.0.0.0/8, but not for this one.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The OSPF 10.0.0.0/8 route
Why it's wrong here
This is wrong because the /8 is less specific than the matching /16.
When this WOULD be correct
In a different scenario where the OSPF route 10.0.0.0/8 is the only available route and no more specific routes exist for 10.10.20.1, the OSPF route would be used. For example, if a question stated that the static route was removed or invalidated, then the OSPF route would be the correct answer.
- ✓
The static 10.10.0.0/16 route
Why this is correct
This is correct because it is the more specific matching route.
- ✗
The default route if present
Why it's wrong here
This is wrong because more specific matching routes already exist.
When this WOULD be correct
If the question stated that the router has no specific routes for 10.10.20.1 and only a default route configured, then the default route would be used for traffic to that destination. This would occur in a scenario where the static and OSPF routes were not present.
- ✗
Neither route, because the networks overlap
Why it's wrong here
This is wrong because overlapping prefixes are normal and longest-prefix match resolves the decision.
When this WOULD be correct
In a different scenario, if the question stated that both routes were configured with conflicting subnet masks or if the OSPF route was incorrectly configured to include the 10.10.0.0/16 range, then this option could be correct, indicating that neither route is usable due to overlap.
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.
✓The static 10.10.0.0/16 routeCorrect answer▾
Why this is correct
This is correct because it is the more specific matching route.
✗The OSPF 10.0.0.0/8 routeWrong answer — click to see why▾
Why this is wrong here
The OSPF route 10.0.0.0/8 is less specific (longer prefix length /8) than the static route 10.10.0.0/16 for the destination 10.10.20.1. The longest prefix match rule dictates that the route with the longest matching prefix (most specific) is chosen, regardless of administrative distance or routing protocol.
★ When this WOULD be the correct answer
In a different scenario where the OSPF route 10.0.0.0/8 is the only available route and no more specific routes exist for 10.10.20.1, the OSPF route would be used. For example, if a question stated that the static route was removed or invalidated, then the OSPF route would be the correct answer.
Why candidates choose this
Students might think that OSPF, as a dynamic routing protocol, is preferred over a static route, or they might confuse administrative distance with prefix length. They may also incorrectly assume that a larger network range (like /8) automatically takes precedence.
✗The default route if presentWrong answer — click to see why▾
Why this is wrong here
A default route (0.0.0.0/0) is only used when no other more specific route matches the destination. Since there are matching routes (10.10.0.0/16 and 10.0.0.0/8) for 10.10.20.1, the default route is not considered. The longest prefix match rule selects the most specific route among those that match.
★ When this WOULD be the correct answer
If the question stated that the router has no specific routes for 10.10.20.1 and only a default route configured, then the default route would be used for traffic to that destination. This would occur in a scenario where the static and OSPF routes were not present.
Why candidates choose this
Students may think that a default route is always used as a last resort, but they might forget that it only applies when no other route matches. They might also confuse the concept of 'default' with 'most preferred' or assume it overrides other routes.
✗Neither route, because the networks overlapWrong answer — click to see why▾
Why this is wrong here
Overlapping prefixes are common in routing tables and do not prevent route selection. The router uses the longest prefix match algorithm to choose the most specific route. Both routes are valid and can coexist; the router simply picks the best match for each destination.
★ When this WOULD be the correct answer
In a different scenario, if the question stated that both routes were configured with conflicting subnet masks or if the OSPF route was incorrectly configured to include the 10.10.0.0/16 range, then this option could be correct, indicating that neither route is usable due to overlap.
Why candidates choose this
Students might think that overlapping routes cause a conflict or error, similar to overlapping IP addresses on interfaces. They may not understand that routing tables can have multiple overlapping entries and that the longest match resolves the ambiguity.
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
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
Learn chapter
OSPFv3 Single-Area Configuration for IPv6
Key term
OSPF
OSPF is a link-state routing protocol used to find the best path for data packets to travel across IP networks, like a smart GPS that recalculates routes when traffic changes.
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.
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JA
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.