hardMultiple ChoiceObjective-mapped
300-410 Practice Question: An experienced network engineer configures mutual…
An experienced network engineer configures mutual redistribution between OSPF and EIGRP on a router. Both protocols have routes to the same prefix, but after redistribution, a routing loop occurs. The engineer did not use route tagging. 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
✓
The redistribute command without route-map or tag allows routes to be re-advertised back into the source protocol, creating a loop.
Without route tagging, redistributed routes are re-injected back into the original protocol, causing a feedback loop. Administrative distance comparison (OSPF 110 vs EIGRP 90/170) can cause suboptimal path selection, but the loop is primarily due to lack of tagging and filtering.
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 routes to be rejected.
Why it's wrong here
Missing seed metric prevents redistribution, not loops.
- ✓
The redistribute command without route-map or tag allows routes to be re-advertised back into the source protocol, creating a loop.
Why this is correct
Mutual redistribution without tagging and filtering causes a feedback loop.
- ✗
OSPF has a lower administrative distance than EIGRP, so OSPF routes are always preferred.
Why it's wrong here
AD affects path selection but does not directly cause redistribution loops.
- ✗
EIGRP stub configuration on the redistributing router prevents routes from being advertised.
Why it's wrong here
Stub restricts query propagation, not redistribution loops.
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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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