hardMultiple Choice
300-410 Practice Question: An engineer configures mutual redistribution…
An engineer configures mutual redistribution between EIGRP and OSPF on a router. EIGRP routes are redistributed into OSPF with a route-map that sets metric-type type-1, and OSPF routes are redistributed into EIGRP with default metric 10000 100 255 1 1500. Unexpectedly, the router starts flapping routes between the two protocols, causing instability. Which is the most likely explanation?
⚠ Common exam trap
300-410 often tests the misconception that mutual redistribution works without loop prevention; candidates may blame metric incompatibility or missing parameters instead of recognizing the need for route tags to break the redistribution feedback loop.
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 redistribution is not using route tags, so routes are being re-redistributed back and forth, causing route flapping.
Mutual redistribution without route tagging causes routes to be redistributed back and forth between EIGRP and OSPF, creating a feedback loop. A route learned from OSPF is redistributed into EIGRP, then learned back from EIGRP into OSPF, and so on, causing the route to flap as metrics and path attributes change. Route tags are the standard mechanism to prevent this by marking routes with a tag on redistribution and denying routes with that tag on the reverse redistribution.
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 redistribution is not using route tags, so routes are being re-redistributed back and forth, causing route flapping.
Why this is correct
Without route tags, each protocol re-advertises the other's routes back, creating a mutual redistribution loop. The stem's flapping stems from this feedback: EIGRP-learned routes return via OSPF and vice versa. Tagging redistributed routes and denying tagged routes on the reciprocal redistribution breaks the cycle.
- ✗
The OSPF metric-type type-1 is incompatible with EIGRP, causing the route to be rejected.
Why it's wrong here
EIGRP accepts OSPF type-1 metrics without rejection; the metric-type value is irrelevant to EIGRP's own metric calculation. Type-1 is chosen when external OSPF cost should accumulate internal cost, but here the loop arises from routes being fed back and forth between the two domains.
- ✗
The EIGRP default metric is missing the reliability and load values, so redistribution fails.
Why it's wrong here
EIGRP's fifth K-value (MTU) is not used in metric calculation, and reliability/load default to 0 when omitted, so redistribution still succeeds. The flapping stems from the mutual redistribution loop, not a malformed metric tuple. The five-value syntax is genuinely required for EIGRP redistribution, making this plausible.
- ✗
The router must have `redistribute connected` under both protocols to avoid flapping.
Why it's wrong here
Redistributing connected networks does nothing to break the mutual redistribution feedback loop between EIGRP and OSPF; it merely injects additional prefixes. The instability arises from routes learned from one protocol being fed back into the other. Connected redistribution is relevant when advertising directly attached subnets into a routing domain.
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.