hardMultiple Choice
300-410 Practice Question: An engineer configures mutual redistribution…
An engineer configures mutual redistribution between OSPF and EIGRP. After a few minutes, the network becomes unstable with routing loops. The engineer checks the routing tables and notices that the same prefix is being learned from both protocols with different administrative distances. Which is the most likely explanation?
⚠ Common exam trap
The trap is blaming administrative distance or missing metrics; the exam expects you to recognize that mutual redistribution without loop prevention (tags/filters) is the root cause of instability.
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
✓
Routes are redistributed back and forth between OSPF and EIGRP without any filtering or tagging
Mutual redistribution without route filtering or tagging causes routes to be fed from OSPF into EIGRP and then back from EIGRP into OSPF (and vice versa), creating a feedback loop. This results in inconsistent routing information, flapping, and potential loops. The fix is to use route maps with tags or distribute-lists to prevent re-advertisement of routes learned from the other protocol.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Routes are redistributed back and forth between OSPF and EIGRP without any filtering or tagging
Why this is correct
Mutual redistribution without route tagging or filtering lets each protocol re-advertise prefixes learned from the other, so OSPF and EIGRP keep feeding routes back and forth. Administrative distance only breaks ties between protocols; it cannot stop the feedback loop, which is why the network destabilises and loops.
- ✗
The seed metric for OSPF redistribution into EIGRP is not configured
Why it's wrong here
An unset seed metric causes EIGRP to reject redistributed OSPF routes entirely, so they would be absent rather than looping. It is tempting because seed metrics are a genuine redistribution requirement, but the stem describes the same prefix learned via both protocols, which points to a tagging or filtering omission.
- ✗
The administrative distance of OSPF is lower than EIGRP, causing OSPF routes to be preferred
Why it's wrong here
Administrative distance only governs which route enters the routing table; it does not cause the same prefix to be redistributed back and forth. It is tempting because AD values are visible in the routing table, but the loop arises from routes being fed back into their source protocol without route tags or filters.
- ✗
The redistribute command is missing the subnets keyword under OSPF
Why it's wrong here
The subnets keyword affects which OSPF routes are redistributed into EIGRP, not the mutual feedback that creates loops. It is tempting because missing subnets does cause incomplete redistribution, but that yields missing routes rather than the same prefix oscillating between protocols with differing administrative distances.
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.
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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.