CCNA IP Routing Practice Question
A router learns 172.16.40.0/24 from OSPF with AD 110 and metric 20. It also learns the same prefix from EIGRP with AD 90 and feasible distance 30720. Which route is installed?
⚠ Common exam trap
A frequent exam trap is assuming that the route with the lower metric value is always preferred, regardless of the routing protocol. In this question, the OSPF route has a metric of 20, which seems better than EIGRP's feasible distance of 30720. However, Cisco routers do not compare metrics across different protocols. Instead, they rely on administrative distance to choose the best route. Mistaking metric comparison for cross-protocol route selection can lead to choosing the wrong answer and misunderstanding how Cisco routing decisions work.
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 EIGRP route because its administrative distance is lower
When the same prefix is learned from different routing protocols, the router compares administrative distance first. EIGRP internal routes have AD 90, which beats OSPF AD 110, so the EIGRP path goes into the table.
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 route because metric 20 is lower than 30720
Why it's wrong here
Comparing OSPF's metric of 20 to EIGRP's feasible distance of 30720 is invalid because each routing protocol uses a completely different metric calculation. OSPF calculates cost from interface bandwidth, whereas EIGRP uses a composite formula based on bandwidth and delay, so these numbers are not directly comparable. The router does not attempt to compare metrics across protocols; it first selects the route with the lowest administrative distance. Since EIGRP's AD of 90 is lower than OSPF's 110, the metric values are irrelevant to the final decision.
When this WOULD be correct
In a different scenario where the router has a configuration that prioritizes metrics over administrative distances, such as a custom route selection policy that favors lower metrics for specific protocols, this option could be correct. For example, if both routes had the same AD and the question specified that the metric should be the deciding factor, then the OSPF route would be chosen.
- ✓
The EIGRP route because its administrative distance is lower
Why this is correct
The EIGRP route is installed because Cisco routers compare administrative distance (AD) before any metric when two different routing protocols advertise the same prefix. OSPF has a default AD of 110, while EIGRP's default AD is 90, making EIGRP more trustworthy. Since the router selects the route with the lowest AD, the EIGRP route wins regardless of its metric value. Metrics are only compared among routes from the same protocol.
- ✗
Both routes because ECMP is automatic across different protocols
Why it's wrong here
Equal-cost multipath (ECMP) only applies when multiple routes have the same metric and are learned from the same routing protocol. Here, OSPF and EIGRP are different protocols with different administrative distances, so the router will not consider them for load balancing. Only the single route with the lowest AD is installed in the routing table, and traffic is forwarded along that one path. ECMP cannot occur across different protocols because they are not evaluated on an equal footing.
When this WOULD be correct
In a scenario where a question specifies that both OSPF and EIGRP routes are configured to support ECMP and have the same administrative distance and metric, the exam could correctly state that both routes would be installed for load balancing.
- ✗
Neither route until one is redistributed into the other protocol
Why it's wrong here
Redistribution is not required for a router to install a route learned via OSPF or EIGRP; each protocol independently builds its IP routing table and selects its best route. Redistribution is only used when injecting routes from one routing protocol into another for downstream routers, but it has no bearing on which of the two current routes is chosen for this router. The router simply compares the administrative distance of the two protocols and installs the one with the lower AD. Therefore, route installation and redistribution are separate processes.
When this WOULD be correct
In a question where the routing protocols are configured to not install routes until they are redistributed into the other protocol, or if there are specific constraints preventing the installation of routes from different protocols, this option would be correct.
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 EIGRP route because its administrative distance is lowerCorrect answer▾
Why this is correct
The EIGRP route is installed because Cisco routers compare administrative distance (AD) before any metric when two different routing protocols advertise the same prefix. OSPF has a default AD of 110, while EIGRP's default AD is 90, making EIGRP more trustworthy. Since the router selects the route with the lowest AD, the EIGRP route wins regardless of its metric value. Metrics are only compared among routes from the same protocol.
✗The OSPF route because metric 20 is lower than 30720Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because the route selection process prioritizes administrative distance (AD) over metric values. EIGRP's AD of 90 is lower than OSPF's AD of 110, making the EIGRP route the preferred choice regardless of the metric.
★ When this WOULD be the correct answer
In a different scenario where the router has a configuration that prioritizes metrics over administrative distances, such as a custom route selection policy that favors lower metrics for specific protocols, this option could be correct. For example, if both routes had the same AD and the question specified that the metric should be the deciding factor, then the OSPF route would be chosen.
Why candidates choose this
Candidates may be tempted by this option due to a common misunderstanding of the route selection process, where they focus on the metric without fully considering the impact of administrative distance on route preference.
✗Both routes because ECMP is automatic across different protocolsWrong answer — click to see why▾
Why this is wrong here
This option is wrong because Equal-Cost Multi-Path (ECMP) routing only applies to routes learned from the same routing protocol, not across different protocols like OSPF and EIGRP.
★ When this WOULD be the correct answer
In a scenario where a question specifies that both OSPF and EIGRP routes are configured to support ECMP and have the same administrative distance and metric, the exam could correctly state that both routes would be installed for load balancing.
Why candidates choose this
Candidates might choose this option due to a misunderstanding of ECMP, believing that it applies universally across different routing protocols rather than just within the same protocol.
✗Neither route until one is redistributed into the other protocolWrong answer — click to see why▾
Why this is wrong here
This option is wrong because both routes can be installed in the routing table based on their administrative distance, and redistribution is not a requirement for route installation in this scenario.
★ When this WOULD be the correct answer
In a question where the routing protocols are configured to not install routes until they are redistributed into the other protocol, or if there are specific constraints preventing the installation of routes from different protocols, this option would be correct.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of how routing protocols interact, believing that routes must be redistributed to be considered valid, which can lead to confusion in mixed protocol environments.
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
Metric
A metric is a quantifiable measurement used to assess the performance, health, or status of IT systems, networks, or applications.
Key term
EIGRP
EIGRP is an advanced distance-vector routing protocol that uses bandwidth and delay by default to find the best path for data packets across a computer network.
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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.