350-501 Architecture Practice Question
A service provider operates an MPLS-TE network using RSVP-TE with a full mesh of tunnels between core routers. The network uses OSPF as IGP with traffic engineering extensions. Recently, a new headend router PE-New was added and configured with several TE tunnels to remote destinations. However, some tunnels repeatedly go down after a few minutes and show in the 'down' state with the error 'Tunnel path option 0: no path to destination (TEDB lookup failed)'. The TE tunnels that remain up are those to destinations that are directly connected to the same OSPF area. The network has multiple OSPF areas (area 0, 1, 2) with inter-area routes redistributed. The operator suspects the issue is related to the TEDB (Traffic Engineering Database) not having complete information. Which action is MOST likely to resolve the issue?
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
✓
Change the IGP to IS-IS with wide metrics and enable MPLS-TE on all IS-IS levels
The issue is that OSPF does not flood traffic engineering (TE) information across area boundaries by default. The TEDB on PE-New lacks topology data for inter-area destinations, so tunnel path computation fails. IS-IS, when configured with wide metrics and MPLS-TE enabled on all levels, floods TE link-state information throughout the entire routing domain (both Level-1 and Level-2), ensuring the TEDB is complete. This resolves the problem. Option D (static routes) does not populate the TEDB. Option B does not help because adding loopbacks to OSPF does not provide TE information. Option A (priorities) only affects tunnel setup and preemption, not TEDB completeness.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Increase the tunnel hold-priority and setup-priority values
Why it's wrong here
Priorities affect preemption, not path computation due to missing TEDB.
- ✗
Add the remote loopbacks to OSPF using network statements in area 0
Why it's wrong here
Adding to area 0 helps reachability but not TE; TEDB still limited to area.
- ✓
Change the IGP to IS-IS with wide metrics and enable MPLS-TE on all IS-IS levels
Why this is correct
IS-IS natively propagates TE information across all levels, ensuring TEDB completeness for inter-area tunnels.
- ✗
Configure static routes for the remote destinations on PE-New
Why it's wrong here
Static routes do not add TE information to the TEDB.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-501 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 350-501 exam.