CCNA IP Routing Practice Question
An OSPF router learns a route with metric 20 and another OSPF route to the same destination with metric 30. The prefix length is the same. Which path is preferred?
⚠ Common exam trap
A common exam trap is confusing administrative distance with metric when comparing routes from the same protocol. Candidates might incorrectly think that a higher metric route is rejected or that administrative distance plays a role in choosing between two OSPF routes. In reality, OSPF always prefers the route with the lowest metric, and both routes remain valid candidates. Misunderstanding this can lead to incorrect answers about route selection or route rejection, especially when multiple OSPF routes to the same prefix exist with different metrics.
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 route with metric 20
The OSPF path with metric 20 is preferred because, within the same routing protocol and for the same prefix length, the metric is used to compare candidate paths. In practical terms, the router is not comparing source trust here because both routes come from OSPF. It is comparing OSPF’s own internal path-cost values, and the lower metric wins. This question is about separating administrative distance from metric. Since both routes come from the same protocol, metric is the deciding factor.
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 route with metric 20
Why this is correct
OSPF uses a cost metric based on interface bandwidth, and lower cost indicates a more efficient path. When a router receives multiple OSPF routes to the same destination, it installs the route with the lowest metric into its routing table. Thus, the route with metric 20 is preferred because it offers a shorter or faster path than metric 30. This is standard OSPF path selection behavior, so the correct choice is the 20-metric route.
- ✗
The route with metric 30
Why it's wrong here
The metric of 30 is higher than 20, meaning the path has a higher cumulative cost, typically due to slower links or multiple hops. In OSPF, higher cost is less preferred, so the router would not select this route for forwarding. While it could be stored as a backup or used for equal-cost load balancing if the metrics were equal, that is not the case here. Thus, the route with metric 30 is not the correct answer.
When this WOULD be correct
In a different scenario where OSPF is configured to prefer higher metrics due to specific policy routing or administrative decisions, a question might ask which route is preferred when the metrics are intentionally inverted, making 30 the preferred choice.
- ✗
Both routes are rejected because the metrics differ
Why it's wrong here
This option misunderstands OSPF's metric handling: differing metrics are normal and are the very basis for selecting the best path. The router does not reject routes because the costs differ; instead, it uses the SPF algorithm to calculate the cost to each destination and then selects the lowest-cost route. Both routes remain in the LSDB, but only the best one is placed in the routing table. Therefore, the statement 'both routes are rejected' is false because the router simply chooses one over the other.
When this WOULD be correct
In a scenario where a question specifies that OSPF routes are only accepted if they have the same metric, and both routes have different metrics, it could state that the router rejects all routes that do not meet this criterion, making this option correct.
- ✗
The default route is preferred
Why it's wrong here
A default route is only used when there is no more specific route in the routing table that matches the destination address. Since the router has learned an OSPF route with metric 20 to the specific destination, that route takes precedence based on the longest-prefix match (most specific match) rule. The default route has a prefix length of /0, which is the least specific, so it would only be considered if the specific route were absent. Consequently, the default route is not preferred in this scenario.
When this WOULD be correct
In a different scenario where the question specifies that the OSPF router has no other routes to the destination and the default route is configured, the default route would be preferred over any other routes, including those with higher metrics.
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 route with metric 20Correct answer▾
Why this is correct
OSPF uses a cost metric based on interface bandwidth, and lower cost indicates a more efficient path. When a router receives multiple OSPF routes to the same destination, it installs the route with the lowest metric into its routing table. Thus, the route with metric 20 is preferred because it offers a shorter or faster path than metric 30. This is standard OSPF path selection behavior, so the correct choice is the 20-metric route.
✗The route with metric 30Wrong answer — click to see why▾
Why this is wrong here
OSPF always prefers the route with the lowest metric. A metric of 30 is higher than 20, so it is less preferred and will not be installed in the routing table unless the lower metric route fails.
★ When this WOULD be the correct answer
In a different scenario where OSPF is configured to prefer higher metrics due to specific policy routing or administrative decisions, a question might ask which route is preferred when the metrics are intentionally inverted, making 30 the preferred choice.
Why candidates choose this
Students may mistakenly think that a higher metric indicates a more reliable or recently learned route, but OSPF uses lower metric as the primary tie-breaker for equal prefix lengths.
✗Both routes are rejected because the metrics differWrong answer — click to see why▾
Why this is wrong here
OSPF does not reject routes with differing metrics; instead, it uses the metric to select the best path. Both routes are valid, but only the one with the lowest metric is installed in the routing table.
★ When this WOULD be the correct answer
In a scenario where a question specifies that OSPF routes are only accepted if they have the same metric, and both routes have different metrics, it could state that the router rejects all routes that do not meet this criterion, making this option correct.
Why candidates choose this
Some might confuse OSPF with protocols that require equal metrics for load balancing, but OSPF only load-balances when metrics are equal; differing metrics simply result in a single best path.
✗The default route is preferredWrong answer — click to see why▾
Why this is wrong here
A default route is only used when no specific route to the destination exists. Since the router has two specific OSPF routes to the destination, it will use the best one, not the default.
★ When this WOULD be the correct answer
In a different scenario where the question specifies that the OSPF router has no other routes to the destination and the default route is configured, the default route would be preferred over any other routes, including those with higher metrics.
Why candidates choose this
Students may think that a default route is always preferred as a catch-all, but specific routes always take precedence over default routes in the routing table.
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
Interpreting HSRP and VRRP Operational Status
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.
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.
About these practice questions
One of 1,389 original 200-301 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
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.