The answer is that the next-hop is not reachable via the IGP with an MPLS label. For a BGP VPNv4 route to be selected as best and installed in the VRF routing table, the next-hop must be reachable through the underlying IGP with a valid MPLS label, typically distributed via LDP. If the label is missing or the next-hop is unreachable, BGP marks the route as valid but not best, preventing VRF installation. On the Cisco SPCOR 350-501 exam, this scenario tests your understanding of the BGP best-path selection process for MPLS L3VPNs, where the next-hop reachability check includes both an IGP route and an associated label. A common trap is assuming a valid BGP prefix alone guarantees installation, but the label binding is a separate requirement. Memory tip: think “no label, no table”—if the next-hop lacks an MPLS label, the VPNv4 route stays valid but not best.
350-501 Services Practice Question
This 350-501 practice question tests your understanding of services. 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 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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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.
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 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.
Clue confirmation
The clue words "best", "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The BGP table is full and cannot accept more prefixes.
Common exam trap: answer the scenario, not the keyword
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.
Detailed technical explanation
How to think about this question
In MPLS L3VPN, BGP carries the VPN label in the NLRI, but the transport label (IGP label) must be present for the next-hop to be reachable via LDP or Segment Routing. The 'show bgp vpnv4 unicast vrf <name> <prefix>' output will show 'not best' with a reason such as 'next-hop not reachable via IGP with label'. This often occurs when the route reflector does not have an LDP session to the PE, or when the IGP does not advertise a label for the next-hop address.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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.
Services — This question tests Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this 350-501 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best", "most likely". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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 →
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.
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.
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.