hardMultiple Choice
300-410 Practice Question: An engineer configures mutual redistribution…
An engineer configures mutual redistribution between OSPF and EIGRP on a router. After a few minutes, the router's CPU spikes and routing loops occur. Which is the most likely explanation?
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 redistributed from OSPF into EIGRP are then redistributed back into OSPF, creating a feedback loop.
Mutual redistribution without route tagging or filtering can cause a routing loop. A route redistributed from OSPF into EIGRP can be redistributed back into OSPF, creating a feedback loop. This is a classic redistribution loop.
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 seed metric for EIGRP was not configured, causing the route to be redistributed with an infinite metric.
Why it's wrong here
EIGRP does require a seed metric, but omitting it causes routes to be rejected rather than redistributed with an infinite metric, so no loops or CPU spikes would follow. It is tempting because seed metrics are a genuine redistribution requirement, yet the described symptoms point to feedback between the two routing domains.
- ✗
The administrative distance of the redistributed routes is lower than the original, causing them to be preferred.
Why it's wrong here
Redistributed routes carry the receiving protocol's default administrative distance, not a lowered one, so this mechanism does not explain the loops. It is tempting because administrative distance does govern route preference, but the actual cause is routes being fed back between OSPF and EIGRP without filtering or tagging.
- ✓
Routes redistributed from OSPF into EIGRP are then redistributed back into OSPF, creating a feedback loop.
Why this is correct
Mutual redistribution without filtering or tag-based deny causes prefixes learned from OSPF to re-enter OSPF via EIGRP, so each protocol treats the other's routes as external and re-advertises them endlessly, inflating the topology table and CPU.
- ✗
The OSPF process ID must match on all routers; otherwise, redistribution fails.
Why it's wrong here
OSPF process IDs are locally significant and need not match between routers, so this cannot cause CPU spikes or loops. It is tempting because OSPF areas must match on adjacent interfaces, but redistribution failures stem from missing seed metrics or administrative distance conflicts, not process ID mismatches.
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
About these practice questions
This 300-410 question is part of Courseiva's 1,401-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.