The answer is to check interface errors and discards on the CE router first. This is correct because intermittent connectivity during peak hours in an MPLS network is a classic symptom of congestion at the edge, where CE router interfaces become saturated, leading to CRC errors, runts, and discards as buffers overflow. On the Cisco SPCOR / CCNP Service Provider Core 350-501 exam, this scenario tests your ability to apply the OSI model’s bottom-up troubleshooting methodology, specifically ruling out Layer 1/2 issues before blaming MPLS labels or routing protocols. A common trap is to immediately suspect BGP or LDP problems, but the time-dependent nature—occurring only during peak hours—points squarely to bandwidth exhaustion or physical-layer degradation. Memory tip: “Peak hours, peek at the CE ports” — always start with the customer edge interface counters when the symptom is tied to traffic load.
350-501 Networking Practice Question
This 350-501 practice question tests your understanding of networking. 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 client reports intermittent connectivity issues when accessing a server across a provider MPLS network. The issue occurs only during peak hours. Which component should be checked first?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Interface errors and discards on the CE router.
Intermittent connectivity during peak hours strongly suggests a bandwidth or queuing issue at the edge of the MPLS network. Interface errors (e.g., CRC, runts) and discards on the CE router indicate congestion or Layer 1/2 problems, which are the most common cause of such time-dependent symptoms. Checking this first aligns with the standard troubleshooting methodology of verifying the physical and data-link layers before moving to higher-layer protocols.
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.
✗
BGP peering status between CE and PE.
Why it's wrong here
BGP sessions are usually stable; intermittent issues are more likely due to interface errors.
✗
CPU utilization of the server.
Why it's wrong here
Server CPU is a host issue, not a network root cause.
✓
Interface errors and discards on the CE router.
Why this is correct
Peak traffic can cause output discards or CRC errors, leading to connectivity drops.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
MPLS labels in the core.
Why it's wrong here
MPLS labels are static and do not cause intermittent issues.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the principle that intermittent issues during peak hours are almost always due to congestion or interface errors at the edge, not control-plane or core problems, leading candidates to incorrectly focus on BGP or MPLS labels.
Detailed technical explanation
How to think about this question
Interface discards occur when the output queue is full due to congestion, causing packets to be dropped before transmission. In an MPLS environment, the CE router's egress interface to the PE is a common bottleneck; monitoring 'show interface' for output discards and 'show queueing' for tail drops can pinpoint the issue. Real-world scenarios often involve oversubscribed circuits where traffic shaping or policing on the CE is misconfigured, leading to peak-hour drops that mimic intermittent connectivity.
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 practitioner preparing for the 350-501 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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.
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Interface errors and discards on the CE router. — Intermittent connectivity during peak hours strongly suggests a bandwidth or queuing issue at the edge of the MPLS network. Interface errors (e.g., CRC, runts) and discards on the CE router indicate congestion or Layer 1/2 problems, which are the most common cause of such time-dependent symptoms. Checking this first aligns with the standard troubleshooting methodology of verifying the physical and data-link layers before moving to higher-layer protocols.
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: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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