mediumMultiple Choice
300-410 Practice Question: Is troubleshooting a route redistribution issue…
A network engineer is troubleshooting a route redistribution issue between EIGRP and OSPF. Routers R1 (EIGRP) and R2 (OSPF) are redistributing routes. The engineer notices that some EIGRP external routes (redistributed into EIGRP from another protocol) are not appearing in the OSPF database on R2. The show ip ospf database external command on R2 does not list these prefixes. What is the most likely cause?
⚠ Common exam trap
300-410 often tests the subnets keyword omission as the classic cause of missing subnetted routes in OSPF, tricking candidates who look for more exotic causes like distribute-lists or administrative distance instead of the simple default classful behavior.
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 redistribute eigrp command under OSPF is missing the subnets keyword.
The most likely cause is that the redistribute eigrp command under OSPF is missing the subnets keyword. Without subnets, OSPF only redistributes classful network routes and drops subnetted prefixes, so EIGRP external routes that are subnetted never appear in the OSPF database as external LSAs.
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 redistribute eigrp command under OSPF is missing the subnets keyword.
Why this is correct
Without the subnets keyword, OSPF redistributes only classful major networks, so external EIGRP prefixes with non-classful masks are omitted from the OSPF database. Adding subnets allows those external routes to be advertised and appear in show ip ospf database external.
- ✗
The redistribute eigrp command under OSPF is missing the match external keyword.
Why it's wrong here
Incorrect. The 'match external' keyword is not a valid option for the 'redistribute eigrp' command under OSPF. The correct command does not have such a keyword.
- ✗
EIGRP has a higher administrative distance than OSPF, causing route suppression.
Why it's wrong here
Incorrect. Administrative distance does not affect redistribution; it is used for route selection when multiple routes exist.
- ✗
The OSPF process on R2 has a distribute-list blocking these routes.
Why it's wrong here
Incorrect. While a distribute-list could block routes, it is less likely than the missing 'subnets' keyword, especially given the symptom of external routes not appearing.
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
VRF-Lite and Multi-Protocol BGP
Key term
Route Redistribution Between Protocols
Route redistribution between protocols is the process of taking routes learned from one routing protocol and injecting them into another routing protocol so that networks using different protocols can communicate.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 300-410 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 300-410 exam.