hardMultiple ChoiceObjective-mapped
300-410 Practice Question: Redistributes OSPF routes into EIGRP on Router R1
A network engineer redistributes OSPF routes into EIGRP on Router R1. After redistribution, Router R3, which is an EIGRP neighbor of R1, starts experiencing routing loops for the 192.168.1.0/24 network. R1 configuration: router eigrp 100, redistribute ospf 1 metric 10000 100 255 1 1500, route-map RM-OSPF-to-EIGRP. The route-map sets tag 100. R3 shows: 'show ip route 192.168.1.0' points to R1, but traceroute shows packets looping between R1 and R3. What is the root cause?
⚠ Common exam trap
Cisco often tests the misconception that a low metric or incorrect metric values cause routing loops, when the real issue is the absence of loop-prevention mechanisms like route tagging and filtering in a multi-protocol redistribution scenario.
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 metric is too low, causing the route to be preferred over the OSPF path, but the loop is due to missing route tagging and filtering on redistribution.
The root cause is that the redistributed OSPF routes into EIGRP lack proper route tagging and filtering, causing R3 to re-advertise the 192.168.1.0/24 route back to R1, creating a routing loop. The route-map sets a tag of 100, but without an inbound filter on R1 (e.g., a distribute-list or route-map denying tagged routes), R1 will accept the route from R3, leading to a loop. Option A correctly identifies that the metric is sufficient for the route to be preferred, but the missing loop-prevention mechanism is the core issue.
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 metric is too low, causing the route to be preferred over the OSPF path, but the loop is due to missing route tagging and filtering on redistribution.
Why this is correct
The route-map sets a tag, but without a corresponding filter on the OSPF side (e.g., deny routes with tag 100), the route can be redistributed back into OSPF, creating a loop.
- ✗
The EIGRP metric values are incorrect; the delay value of 100 is too high, causing the route to be considered unreachable.
Why it's wrong here
The metric values are valid; a delay of 100 microseconds is acceptable and does not cause loops.
- ✗
The route-map is applied in the wrong direction; it should be applied to the redistribute command under OSPF instead of EIGRP.
Why it's wrong here
The route-map is correctly applied to the redistribution from OSPF into EIGRP.
- ✗
R3 has a static route for 192.168.1.0/24 pointing to R1, overriding the dynamic route.
Why it's wrong here
No static route is mentioned; the loop is due to redistribution dynamics.
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 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.