350-501 Services Practice Question
A service provider is troubleshooting BGP route advertisement for a VPNv4 prefix. The PE router receives the prefix from the route reflector but does not install it in the VRF routing table. The BGP table shows the prefix as valid but not best. What is the most likely cause?
⚠ Common exam trap
Cisco often tests the distinction between a route being valid (accepted into BGP table) versus best (eligible for installation into the VRF), and the trap here is that candidates assume a valid route should automatically be installed, overlooking the next-hop reachability with label requirement for MPLS VPNs.
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 next-hop is not reachable via the IGP with an MPLS label.
For a VPNv4 prefix to be installed in the VRF routing table, BGP must select it as the best path. A key requirement for best-path selection is that the next-hop address must be reachable via the IGP with an associated MPLS label (via LDP or other label distribution protocol). If the next-hop is not reachable with a label, the route remains valid but not best, and thus is not installed in the VRF.
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 VRF does not have the correct route-target import.
Why it's wrong here
If route-target import were missing, the route would not be valid in BGP.
- ✓
The next-hop is not reachable via the IGP with an MPLS label.
Why this is correct
Next-hop unreachability causes the route to be not best.
- ✗
The BGP table is full and cannot accept more prefixes.
Why it's wrong here
The route is already in the BGP table.
- ✗
The MPLS label is missing in the BGP update.
Why it's wrong here
The route is valid, so label is present.
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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.