- A
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 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.
- B
The EIGRP metric values are incorrect; the delay value of 100 is too high, causing the route to be considered unreachable.
Why wrong: The metric values are valid; a delay of 100 microseconds is acceptable and does not cause loops.
- C
The route-map is applied in the wrong direction; it should be applied to the redistribute command under OSPF instead of EIGRP.
Why wrong: The route-map is correctly applied to the redistribution from OSPF into EIGRP.
- D
R3 has a static route for 192.168.1.0/24 pointing to R1, overriding the dynamic route.
Why wrong: No static route is mentioned; the loop is due to redistribution dynamics.
OSPF to EIGRP Redistribution Loop Prevention
This 300-410 practice question tests your understanding of device management. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
Quick Answer
The root cause is missing route tagging and filtering to prevent the redistributed OSPF routes from being re-advertised back into OSPF, creating a feedback loop. When R1 redistributes OSPF into EIGRP with a route-map that sets tag 100, the tag alone does nothing unless inbound filtering is applied on the EIGRP side or on any mutual redistribution point. Without a distribute-list or a route-map that denies tagged routes on re-redistribution, Router R3—if it also runs OSPF—can learn the EIGRP route and redistribute it back into OSPF, causing R1 to see a better metric for 192.168.1.0/24 via OSPF from R3, thus looping traffic between R1 and R3. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of redistribution loop prevention using administrative distance manipulation or, more reliably, route tagging with filtering. A common trap is assuming a low metric alone causes the loop, but the real issue is the absence of a filter that blocks tagged routes from re-entering OSPF. Memory tip: “Tag it, then block it—if you tag without a lock, the loop will mock.”
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
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.
- ✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
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.
Detailed technical explanation
How to think about this question
In EIGRP, route tagging is a common mechanism to prevent redistribution loops; when a route is redistributed from OSPF into EIGRP with a tag, other EIGRP routers should be configured to not re-advertise that tagged route back to the source. Without a distribute-list or route-map filtering inbound updates based on the tag, the route can be learned back via EIGRP from a neighbor, creating a feedback loop. In real-world deployments, this is often mitigated by setting a tag on redistributed routes and then applying a distribute-list with a deny statement for that tag on the inbound EIGRP interface.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Device Management — study guide chapter
Learn the concepts, then practise the questions
- →
Device Management practice questions
Targeted practice on this topic area only
- →
All 300-410 questions
2,152 questions across all exam domains
- →
Cisco CCNP ENARSI 300-410 study guide
Full concept coverage aligned to exam objectives
- →
300-410 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 300-410 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Layer 3 Technologies practice questions
Practise 300-410 questions linked to Layer 3 Technologies.
EIGRP Troubleshooting practice questions
Practise 300-410 questions linked to EIGRP Troubleshooting.
OSPF Troubleshooting (v2/v3) practice questions
Practise 300-410 questions linked to OSPF Troubleshooting (v2/v3).
BGP Troubleshooting practice questions
Practise 300-410 questions linked to BGP Troubleshooting.
Route Redistribution practice questions
Practise 300-410 questions linked to Route Redistribution.
Policy-Based Routing (PBR) practice questions
Practise 300-410 questions linked to Policy-Based Routing (PBR).
VRF-Lite practice questions
Practise 300-410 questions linked to VRF-Lite.
Route Maps and Route Filtering practice questions
Practise 300-410 questions linked to Route Maps and Route Filtering.
Administrative Distance practice questions
Practise 300-410 questions linked to Administrative Distance.
Route Summarization practice questions
Practise 300-410 questions linked to Route Summarization.
Bidirectional Forwarding Detection (BFD) practice questions
Practise 300-410 questions linked to Bidirectional Forwarding Detection (BFD).
VPN Technologies practice questions
Practise 300-410 questions linked to VPN Technologies.
Practice this exam
Start a free 300-410 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this 300-410 question test?
Device Management — This question tests Device Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this 300-410 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Keep practising
More 300-410 practice questions
- Drag and drop the steps to negotiate an IKEv2 IPsec site-to-site tunnel into the correct order, from first to last.
- Drag and drop the steps to troubleshoot an IPsec site-to-site VPN adjacency failure into the correct order, from first t…
- Drag and drop the steps to verify and validate the operational state of an IPsec site-to-site VPN into the correct order…
- Consider the following configuration snippet: ip cef ! interface GigabitEthernet0/0 ip address 10.0.0.1 255.255.255.25…
- A router is configured with 'logging host 10.1.1.100' and 'logging trap informational'. The engineer notices that syslog…
- Drag and drop the steps to configure a GRE tunnel for IPv6 over IPv4 into the correct order, from first to last.
Last reviewed: Jul 4, 2026
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.