The answer is that BGP-LS uses BGP as the transport protocol, operating with a separate address family (AFI 16388 / SAFI 71) distinct from VPNv4 (AFI 1 / SAFI 128). This separation is critical because it allows BGP-LS to carry link-state information from IGPs like OSPF or IS-IS without interfering with MPLS VPN signaling, enabling controllers and applications to collect network topology data independently. On the Cisco SPCOR / CCNP Service Provider Core 350-501 exam, this question tests your understanding of how BGP-LS extends BGP to distribute IGP topology, often appearing as a multi-select item where a common trap is confusing its address family with VPNv4 or assuming it replaces the IGP entirely. A reliable memory tip is to think of BGP-LS as a "topology taxi" that uses BGP as the vehicle but runs on its own dedicated lane (AFI 16388 / SAFI 71), separate from the VPNv4 highway.
350-501 Services Practice Question
This 350-501 practice question tests your understanding of services. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Which THREE characteristics apply to the BGP-LS (BGP Link State) protocol?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It uses a separate address family from VPNv4.
BGP-LS uses a separate address family (AFI 16388 / SAFI 71) from VPNv4 (AFI 1 / SAFI 128) to carry link-state information. This separation allows BGP-LS to operate independently from VPNv4 routes, enabling the collection and distribution of IGP topology data without interfering with MPLS VPN signaling.
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.
Read the scenario before looking for a memorised answer.
✗
It carries traffic-engineering parameters in the NLRI.
Why it's wrong here
TE parameters are carried in the BGP-LS attribute, not NLRI.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that BGP-LS only supports IS-IS (Option A) or that TE parameters are carried in the NLRI (Option E), when in fact BGP-LS supports both OSPF and IS-IS, and TE attributes are carried as sub-TLVs within the BGP-LS path attribute, not directly in the NLRI.
Detailed technical explanation
How to think about this question
BGP-LS (RFC 7752) uses BGP as a transport protocol to collect link-state information from IGPs (OSPF and IS-IS) and distribute it to controllers or applications like Path Computation Element (PCE). The protocol encodes IGP topology into BGP NLRI with three types: Node NLRI, Link NLRI, and Prefix NLRI, each carrying specific descriptors and optional sub-TLVs for TE metrics. In real-world SDN deployments, BGP-LS enables a centralized controller to build a complete view of the network topology without running an IGP on the controller itself.
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 network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
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: It uses a separate address family from VPNv4. — BGP-LS uses a separate address family (AFI 16388 / SAFI 71) from VPNv4 (AFI 1 / SAFI 128) to carry link-state information. This separation allows BGP-LS to operate independently from VPNv4 routes, enabling the collection and distribution of IGP topology data without interfering with MPLS VPN signaling.
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.
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.