hardMultiple ChoiceObjective-mapped
300-410 Practice Question: In an MPLS network, Router R1 is a provider edge…
In an MPLS network, Router R1 is a provider edge (PE) router that redistributes BGP routes into OSPF. The network experiences intermittent loss of reachability to a specific prefix 10.10.10.0/24. R1 configuration includes: 'router ospf 1 redistribute bgp 65000 subnets metric-type 1' and 'router bgp 65000 neighbor 10.0.0.2 route-map SET-METRIC in' with a route-map that sets metric 100. R2, a P router, shows 'show ip route 10.10.10.0' output: 'O E1 10.10.10.0/24 [110/20] via 10.0.0.1, 00:00:15' but traffic fails. 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 OSPF redistribute command lacks the 'metric' keyword to use the BGP metric; default metric 20 is used, causing inconsistency.
The route-map applied to BGP inbound sets metric 100, but redistribution into OSPF uses the BGP metric as the OSPF cost. However, OSPF external route cost is calculated as metric-type 1 cost plus internal cost to the ASBR. The OSPF cost of 20 indicates the BGP metric is not being used correctly; instead, the default metric of 20 is applied because the 'metric' keyword is missing in the redistribute command, causing suboptimal path and potential blackholing due to metric mismatch.
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 route-map SET-METRIC is not applied to the correct neighbor direction; it should be outbound.
Why it's wrong here
Incorrect direction; inbound sets metric on received routes, which is correct for redistribution.
- ✓
The OSPF redistribute command lacks the 'metric' keyword to use the BGP metric; default metric 20 is used, causing inconsistency.
Why this is correct
Without 'metric' in redistribute, OSPF uses default metric 20, ignoring the BGP metric set by route-map, leading to incorrect cost and potential routing loops.
- ✗
The OSPF network type mismatch on the link between R1 and R2 causes adjacency issues.
Why it's wrong here
No evidence of adjacency issues; the route is present.
- ✗
The BGP neighbor 10.0.0.2 is not reachable due to ACL blocking.
Why it's wrong here
No ACL mentioned; BGP session is up if routes are received.
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.
Go deeper
Related to this question
Learn chapter
Introduction to ENARSI Exam and Network Fundamentals
Key term
LDP Protocol
LDP, or Label Distribution Protocol, is a protocol that routers use to automatically exchange labels that enable MPLS (Multiprotocol Label Switching) to create fast, efficient paths for data packets across a network.
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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.