- A
Upgrade OSPF to OSPFv3 to support IPv6 and improve performance
Why wrong: OSPFv3 is for IPv6 and does not inherently reduce LSDB size or improve convergence.
- B
Implement Segment Routing (SR-MPLS) to replace LDP and reduce IGP overhead
SR-MPLS eliminates LDP and reduces IGP LSDB size because SIDs are advertised as TLV extensions, reducing the number of LSA types.
- C
Introduce IS-IS as a second IGP to offload traffic from OSPF, and use route redistribution between the two protocols
Why wrong: Running two IGPs increases complexity and does not reduce the LSDB size; redistribution can cause loops.
- D
Replace OSPF with BGP as the core IGP to reduce link-state overhead
Why wrong: BGP is not designed as an IGP; it would require a full mesh or route reflectors and would not improve convergence.
Quick Answer
The correct approach is to implement Segment Routing (SR-MPLS) to replace LDP and reduce IGP overhead. This works because SR-MPLS encodes MPLS labels directly into OSPF or IS-IS extensions, eliminating the need for a separate label distribution protocol like LDP. By doing so, it slashes control-plane signaling, shrinks the OSPF link-state database, and accelerates convergence—directly solving the large LSDB and slow LDP session establishment described in the scenario. On the Cisco SPCOR 350-501 exam, this question tests your understanding of how SR-MPLS addresses IGP scalability issues in large service provider networks, often appearing as a scenario where you must choose between maintaining LDP, migrating to IS-IS, or deploying SR-MPLS. A common trap is assuming that simply splitting the OSPF area or upgrading hardware is sufficient, but the key insight is that SR-MPLS removes the LDP dependency entirely, reducing protocol overhead without hardware changes. Memory tip: “SR kills LDP” — think of Segment Routing as a direct label-to-IGP mapping that cuts out the middleman protocol.
350-501 Architecture Practice Question
This 350-501 practice question tests your understanding of architecture. 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.
You are a network architect for a large service provider. The network consists of multiple core routers (P routers) and edge routers (PE routers) supporting both L3VPN and L2VPN services. The network currently uses LDP for label distribution and has a flat IGP (OSPF) design. Recently, there have been scalability issues: the IGP convergence time has increased significantly, and the OSPF link-state database (LSDB) has grown large, causing high CPU utilization on core routers. Additionally, the LDP sessions are taking longer to establish after a router reboot. You are tasked with redesigning the network to improve scalability and convergence. The budget allows for significant changes but cannot replace all hardware. Which approach best addresses the scalability issues while minimizing disruption?
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.
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
Implement Segment Routing (SR-MPLS) to replace LDP and reduce IGP overhead
Segment Routing (SR-MPLS) eliminates the need for LDP by encoding MPLS labels directly in the IGP (OSPF or IS-IS) using extensions, which reduces control-plane overhead and speeds up convergence. This directly addresses the large OSPF LSDB and slow LDP session establishment because SR-MPLS does not require a separate label distribution protocol and can leverage a single IGP for both routing and label information, improving scalability without hardware replacement.
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.
- ✗
Upgrade OSPF to OSPFv3 to support IPv6 and improve performance
Why it's wrong here
OSPFv3 is for IPv6 and does not inherently reduce LSDB size or improve convergence.
- ✓
Implement Segment Routing (SR-MPLS) to replace LDP and reduce IGP overhead
Why this is correct
SR-MPLS eliminates LDP and reduces IGP LSDB size because SIDs are advertised as TLV extensions, reducing the number of LSA types.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Introduce IS-IS as a second IGP to offload traffic from OSPF, and use route redistribution between the two protocols
Why it's wrong here
Running two IGPs increases complexity and does not reduce the LSDB size; redistribution can cause loops.
- ✗
Replace OSPF with BGP as the core IGP to reduce link-state overhead
Why it's wrong here
BGP is not designed as an IGP; it would require a full mesh or route reflectors and would not improve convergence.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that adding a second IGP or upgrading to OSPFv3 will improve scalability, when in fact the real issue is the overhead of a separate label distribution protocol (LDP) and the LSDB size, which Segment Routing directly addresses by integrating label distribution into the IGP.
Detailed technical explanation
How to think about this question
SR-MPLS uses IGP extensions (e.g., OSPF extensions per RFC 8665 or IS-IS extensions per RFC 8667) to advertise prefix-SIDs and adjacency-SIDs, allowing label-switched paths to be computed from the IGP alone. This removes the need for LDP session establishment and maintenance, which is particularly beneficial after a router reboot because the IGP converges first and labels are immediately available. In real-world service provider networks, SR-MPLS also enables TI-LFA (Topology-Independent Loop-Free Alternate) for sub-50ms fast reroute, further improving convergence without additional protocols.
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.
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FAQ
Questions learners often ask
What does this 350-501 question test?
Architecture — This question tests Architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Implement Segment Routing (SR-MPLS) to replace LDP and reduce IGP overhead — Segment Routing (SR-MPLS) eliminates the need for LDP by encoding MPLS labels directly in the IGP (OSPF or IS-IS) using extensions, which reduces control-plane overhead and speeds up convergence. This directly addresses the large OSPF LSDB and slow LDP session establishment because SR-MPLS does not require a separate label distribution protocol and can leverage a single IGP for both routing and label information, improving scalability without hardware replacement.
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". 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.
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Last reviewed: Jun 11, 2026
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.
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