hardMultiple ChoiceObjective-mapped
300-410 Practice Question: Notices that after redistributing EIGRP into…
A network engineer notices that after redistributing EIGRP into OSPF, a routing loop occurs between two routers. Router R1 config:
router ospf 1
redistribute eigrp 100 subnets !
router eigrp 100
redistribute ospf 1 metric 10000 100 255 1 1500
R1# show ip route 192.168.1.0
Routing entry for 192.168.1.0/24 Known via "eigrp 100", distance 90, metric 128256 Redistributing via eigrp 100 Last update from 10.1.1.2 on GigabitEthernet0/0
R2# show ip route 192.168.1.0
Routing entry for 192.168.1.0/24 Known via "ospf 1", distance 110, metric 20 Redistributing via ospf 1 Last update from 10.1.1.1 on GigabitEthernet0/0
What is the root cause?
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 commands are missing route-map filters, causing mutual redistribution and a loop.
Mutual redistribution between EIGRP and OSPF without route filtering causes a routing loop. R1 learns the route via EIGRP and redistributes into OSPF; R2 learns via OSPF and redistributes back into EIGRP, creating a loop. The fix is to use route-maps to filter redistributed routes or set administrative distance to prefer one source.
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 redistribute commands are missing route-map filters, causing mutual redistribution and a loop.
Why this is correct
Without filtering, routes learned from one protocol are redistributed back, creating a loop.
- ✗
The EIGRP metric is too low, causing OSPF to prefer the redistributed route.
Why it's wrong here
The metric is fine; the loop is due to mutual redistribution, not metric.
- ✗
The OSPF administrative distance is higher than EIGRP, causing suboptimal path selection.
Why it's wrong here
Distance difference is normal; the loop is due to redistribution without filters.
- ✗
The subnets keyword under OSPF redistribution is causing classful behavior.
Why it's wrong here
The subnets keyword allows classless routes; it does not cause 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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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.