CCNA IP Routing Practice Question
A router learns the same destination prefix from OSPF and from a static route configured with administrative distance 90. Which route is preferred by default?
⚠ Common exam trap
A frequent exam trap is believing that dynamic routing protocols like OSPF always take precedence over static routes. Many candidates mistakenly think that dynamic routes inherently override static routes regardless of administrative distance. However, Cisco routers use administrative distance as the primary factor in route selection, not the route source type. Since the static route in this question has an AD of 90, which is lower than OSPF’s default 110, the static route is preferred. Misunderstanding this can lead to incorrect answers and confusion about route installation in the routing table.
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 route with distance 90
The static route is preferred because its administrative distance of 90 is lower than OSPF’s default administrative distance of 110. In practical terms, when the prefix length is the same, the router compares route-source trust next. The lower administrative distance wins. This question is important because many learners remember that static routes are often strong choices but forget that administrative distance can be tuned. Here, that tuning explicitly makes the static route more preferred than OSPF.
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 static route with distance 90
Why this is correct
The static route with distance 90 is correct because administrative distance is the tiebreaker for routes to the same prefix from different sources. OSPF has a default administrative distance of 110, which represents a lower trustworthiness than the explicitly configured value of 90. Since lower administrative distance is preferred, the router installs the static route in the routing table. The source being static is not the reason; the configured distance value is what makes it win.
- ✗
The OSPF route, because dynamic routes always beat static routes
Why it's wrong here
Dynamic routes do not automatically outrank static routes; that belief ignores how administrative distance works. Route preference is determined solely by the numeric administrative distance, not by whether the route was learned dynamically or configured manually. In this scenario, the static route's distance of 90 is lower than OSPF's 110, so the static route is more trusted. Therefore, OSPF is not installed because dynamic learning does not confer an inherent advantage.
When this WOULD be correct
In a different question setup where OSPF is configured with a lower administrative distance than the static route (e.g., OSPF at 80 and static at 90), the OSPF route would be preferred, making this option correct. The question would need to specify that the OSPF route has a lower administrative distance.
- ✗
Both routes equally, because the prefix is identical
Why it's wrong here
Having the same prefix length does not mean both routes are equally preferred, because routes from different protocols are compared using administrative distance. OSPF's default administrative distance is 110, while this static route has a distance of 90. The router does not aggregate or load-balance across protocols; it installs only the route with the lower administrative distance. Thus the identical prefix length has no bearing on equality when the administrative distances differ.
When this WOULD be correct
In a different scenario, if a question stated that both routes had the same administrative distance and the router was configured to load balance between equal-cost paths, then this option could be correct as both routes would be considered equally valid for forwarding traffic.
- ✗
Neither route, because duplicate information is dropped
Why it's wrong here
Routers do not simply drop duplicate routing information; they perform a route-selection process. For the same destination prefix, the router compares administrative distances across different sources and installs the winning route in the forwarding table. The losing route remains in the originating protocol's database, not in the routing table. Therefore, duplicate information is not dropped; it is evaluated and only the best route is chosen.
When this WOULD be correct
In a scenario where a router is configured to drop duplicate routes due to a specific policy or configuration, such as using route filtering or specific routing protocol settings, this option could be correct. For example, if the question states that the router is configured to ignore duplicate routes from OSPF, then neither route would be preferred.
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 route with distance 90Correct answer▾
Why this is correct
The static route with distance 90 is correct because administrative distance is the tiebreaker for routes to the same prefix from different sources. OSPF has a default administrative distance of 110, which represents a lower trustworthiness than the explicitly configured value of 90. Since lower administrative distance is preferred, the router installs the static route in the routing table. The source being static is not the reason; the configured distance value is what makes it win.
✗The OSPF route, because dynamic routes always beat static routesWrong answer — click to see why▾
Why this is wrong here
Route preference is determined by administrative distance, not by whether the route is learned dynamically or statically. A static route with a lower AD is preferred over a dynamic route with a higher AD.
★ When this WOULD be the correct answer
In a different question setup where OSPF is configured with a lower administrative distance than the static route (e.g., OSPF at 80 and static at 90), the OSPF route would be preferred, making this option correct. The question would need to specify that the OSPF route has a lower administrative distance.
Why candidates choose this
Students may mistakenly believe that dynamic routing protocols are always superior to static routes because they adapt to network changes, but administrative distance overrides this general notion.
✗Both routes equally, because the prefix is identicalWrong answer — click to see why▾
Why this is wrong here
When two routes have the same prefix length but different administrative distances, the route with the lower AD is installed in the routing table. Equal prefix length does not imply equal preference.
★ When this WOULD be the correct answer
In a different scenario, if a question stated that both routes had the same administrative distance and the router was configured to load balance between equal-cost paths, then this option could be correct as both routes would be considered equally valid for forwarding traffic.
Why candidates choose this
Test-takers might confuse administrative distance with metric or think that identical prefixes lead to load balancing, but AD is the primary tiebreaker for route selection.
✗Neither route, because duplicate information is droppedWrong answer — click to see why▾
Why this is wrong here
Routers do not drop duplicate prefixes; they select the best route based on administrative distance and install it in the routing table. The other route is kept in the routing information source but not used.
★ When this WOULD be the correct answer
In a scenario where a router is configured to drop duplicate routes due to a specific policy or configuration, such as using route filtering or specific routing protocol settings, this option could be correct. For example, if the question states that the router is configured to ignore duplicate routes from OSPF, then neither route would be preferred.
Why candidates choose this
Some may think that duplicate information causes confusion or is discarded, but routers are designed to handle multiple sources for the same prefix and choose the most trustworthy one.
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
CAN
A CAN (Controller Area Network) is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other without a host computer.
Key term
OSPF
OSPF is a link-state routing protocol that uses the SPF algorithm to compute the shortest path to each destination within a single autonomous system.
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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.