mediumMultiple ChoiceObjective-mapped
300-410 Practice Question: Is troubleshooting a route redistribution issue…
A network engineer is troubleshooting a route redistribution issue between OSPF and EIGRP. Routers R1 (OSPF) and R2 (EIGRP) are redistributing routes into each other. The engineer notices that some OSPF external routes are not appearing in the EIGRP topology table on R2, although the redistribution is configured. The show ip eigrp topology command on R2 does not list the missing prefixes. What is the most likely cause?
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 ospf command under EIGRP is missing the match external keyword.
When redistributing from OSPF into EIGRP, by default only OSPF internal routes are redistributed; external OSPF routes (type 5 or 7) are not included unless the match external keyword is specified. This explains why some routes are missing.
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 ospf command under EIGRP is missing the match internal keyword.
Why it's wrong here
The match internal keyword is the default and includes OSPF internal routes, but external routes require match external.
- ✓
The redistribute ospf command under EIGRP is missing the match external keyword.
Why this is correct
Correct: Without match external, OSPF external routes are not redistributed into EIGRP.
- ✗
The OSPF process on R1 has a route filter blocking external routes.
Why it's wrong here
The issue is on the redistributing router (R2), not on R1.
- ✗
EIGRP has a lower administrative distance than OSPF, causing route suppression.
Why it's wrong here
Administrative distance affects route selection, not redistribution of specific route types.
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
Introduction to ENARSI Exam and Network Fundamentals
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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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