CCNA IP Routing Practice Question
Exhibit
R1# show ip route D 10.10.10.0/24 [90/30720] via 192.0.2.2 O 10.10.10.0/24 [110/20] via 192.0.2.6 Destination being tested: 10.10.10.200
Why is traffic to 10.10.10.200 using the EIGRP route instead of the OSPF route, given that both routes have the same prefix length?
⚠ Common exam trap
A common mistake is to assume that OSPF routes always have a lower administrative distance than EIGRP routes.
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
✓
Because EIGRP has a lower administrative distance than OSPF for the same prefix length.
When two routes have the same prefix length, the router uses administrative distance to choose the route with the lowest value. EIGRP has a default administrative distance of 90, while OSPF uses 110. Therefore, the EIGRP route is preferred.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Because EIGRP has a lower administrative distance than OSPF for the same prefix length.
Why this is correct
Both EIGRP and OSPF have learned routes to 10.10.10.0/24, so the prefix lengths are identical, meaning longest-match selection does not break the tie. Cisco's default administrative distance for internal EIGRP is 90, while OSPF's is 110; since lower AD is preferred, the EIGRP route is installed in the routing table. This is the correct explanation of why traffic to 10.10.10.200 uses the EIGRP path.
- ✗
Because OSPF routes are never installed when EIGRP is present.
Why it's wrong here
OSPF routes can absolutely be installed in the routing table when EIGRP is running, provided the OSPF path is the best route (e.g., if EIGRP is not advertising that prefix or has a higher AD). In this scenario, the OSPF route exists as a candidate but is not selected because EIGRP's AD is lower; however, it is still present in the RIB or topology table. The statement falsely claims an absolute prohibition, which is not how multi-protocol routing works; different protocols can coexist and the best route is chosen per prefix.
When this WOULD be correct
In a scenario where the question specifies that OSPF is configured to not participate in routing due to a specific configuration, such as a route map or filtering, this option could be correct. For example, if the question stated that OSPF was disabled or not operational, then EIGRP would be the only routing protocol providing routes.
- ✗
Because OSPF can be used only for IPv6 routes.
Why it's wrong here
OSPFv2 is specifically designed for IPv4, while OSPFv3 handles IPv6; the claim that OSPF is only for IPv6 is factually incorrect. The destination 10.10.10.200 is an IPv4 address, so OSPF is absolutely a valid routing protocol for this traffic. This option fails because it misrepresents OSPF's protocol capabilities, not because of any routing decision logic.
When this WOULD be correct
In a different scenario where the question specifies that only IPv6 routing protocols are being considered, and the traffic is directed to an IPv6 address, this option could be correct if the question implies that OSPF is not configured for IPv6 routes.
- ✗
Because EIGRP routes always have a smaller subnet mask than OSPF routes.
Why it's wrong here
The subnet mask length advertised by a routing protocol is not an inherent property of the protocol itself; both EIGRP and OSPF can carry any valid IPv4 prefix length, from /8 to /32. In this exhibit, both routes are for 10.10.10.0/24, so the mask lengths are equal, not smaller for EIGRP. Routing preference is determined by administrative distance and metric, never by the protocol's typical mask length, making this option both false and irrelevant.
When this WOULD be correct
In a different scenario where the question specifies that EIGRP routes are always configured with a smaller subnet mask than OSPF routes, and the routing decision is based solely on the mask size, this option could be correct. For example, if the question asked why a specific route was preferred due to subnet mask comparison, then this option would apply.
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.
✓Because EIGRP has a lower administrative distance than OSPF for the same prefix length.Correct answer▾
Why this is correct
Both EIGRP and OSPF have learned routes to 10.10.10.0/24, so the prefix lengths are identical, meaning longest-match selection does not break the tie. Cisco's default administrative distance for internal EIGRP is 90, while OSPF's is 110; since lower AD is preferred, the EIGRP route is installed in the routing table. This is the correct explanation of why traffic to 10.10.10.200 uses the EIGRP path.
✗Because OSPF routes are never installed when EIGRP is present.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because OSPF can coexist with EIGRP on the same network, and routes from both protocols can be installed in the routing table based on their administrative distances.
★ When this WOULD be the correct answer
In a scenario where the question specifies that OSPF is configured to not participate in routing due to a specific configuration, such as a route map or filtering, this option could be correct. For example, if the question stated that OSPF was disabled or not operational, then EIGRP would be the only routing protocol providing routes.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of how routing protocols interact, mistakenly believing that the presence of one protocol inherently prevents the installation of routes from another.
✗Because OSPF can be used only for IPv6 routes.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because OSPF can be utilized for both IPv4 and IPv6 routes, making it irrelevant to the question about traffic routing to an IPv4 address (10.10.10.200).
★ When this WOULD be the correct answer
In a different scenario where the question specifies that only IPv6 routing protocols are being considered, and the traffic is directed to an IPv6 address, this option could be correct if the question implies that OSPF is not configured for IPv6 routes.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of OSPF's capabilities, mistakenly believing that it is limited to IPv6, especially if they have encountered questions focused solely on IPv6 routing.
✗Because EIGRP routes always have a smaller subnet mask than OSPF routes.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because EIGRP and OSPF can operate simultaneously with different subnet masks; the route selection is based on administrative distance, not subnet mask size.
★ When this WOULD be the correct answer
In a different scenario where the question specifies that EIGRP routes are always configured with a smaller subnet mask than OSPF routes, and the routing decision is based solely on the mask size, this option could be correct. For example, if the question asked why a specific route was preferred due to subnet mask comparison, then this option would apply.
Why candidates choose this
Candidates may choose this option due to a common misconception that EIGRP's efficiency is tied to its subnet mask size, leading them to overlook the fundamental routing decision factor of administrative distance.
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
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.
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.