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300-410 Practice Question: Is troubleshooting MPLS traffic engineering (TE)…
A network engineer is troubleshooting MPLS traffic engineering (TE) tunnels. A TE tunnel from Router A to Router B is configured but remains down. The engineer runs show mpls traffic-eng tunnels and sees that the tunnel is in 'down' state with the error 'Path computation failed'. The IGP is OSPF with MPLS TE enabled, and the network is fully meshed. What is the most likely 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
✓
MPLS TE is not enabled on all interfaces along the path.
The 'Path computation failed' error indicates that the headend router cannot find a path meeting the constraints. Since OSPF TE is enabled, the issue is likely that the traffic engineering database (TED) is incomplete because MPLS TE is not enabled on all intermediate interfaces, preventing the headend from learning link attributes.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
MPLS TE is not enabled on all interfaces along the path.
Why this is correct
Correct because MPLS TE must be enabled on each interface to advertise link attributes into the TED; otherwise, the headend cannot compute a constraint-based path.
- ✗
The tunnel destination is not reachable via the IGP.
Why it's wrong here
Incorrect because the tunnel destination is a TE tunnel headend; reachability is not required for TE path computation, only the TED.
- ✗
RSVP is not configured on the tunnel interface.
Why it's wrong here
Incorrect because RSVP is used for signaling, but the path computation fails before signaling; RSVP configuration is not the cause of computation failure.
- ✗
The tunnel bandwidth is set too high, exceeding available bandwidth.
Why it's wrong here
Incorrect because while bandwidth constraints can cause path computation failure, the error message 'Path computation failed' without specific bandwidth details suggests a more fundamental issue like missing TE configuration.
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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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.