The answer is misconfigured CoS-to-queue mapping on the IPN switches. In a Cisco ACI multi-pod design, the IPN switches act as Layer 3 transit devices that must trust and preserve the CoS markings applied by the ACI fabric to maintain low latency between pods. When these CoS values are not correctly mapped to the appropriate egress queues, application traffic can suffer buffer drops and latency spikes even when the underlay has sufficient bandwidth and APIC health scores remain high. This scenario tests your understanding of ACI multi-pod latency and QoS on IPN switches, a common trap on the Cisco DCCOR / CCNP Data Center Core 350-601 exam where candidates often overlook that IPN switches require explicit QoS policies to honor the fabric’s priority handling. Remember: the IPN is the handoff—if CoS isn’t mapped, latency gets unmapped.
350-601 Network Practice Question
This 350-601 practice question tests your understanding of network. 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 large enterprise data center is deploying a new application using Cisco ACI with a multi-pod design. The application requires low-latency communication between servers in different pods. The network team has configured the ACI fabric with two pods, each connected via inter-pod network (IPN) switches. After deployment, the application experiences intermittent latency spikes and packet loss. The APIC health scores remain high but the latency issue persists. The team has verified the underlay IP connectivity and MTU settings. What is the most likely cause of the latency issues?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
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 CoS settings for the application traffic are not properly mapped to the appropriate queue on the IPN switches.
In a Cisco ACI multi-pod design, the IPN switches must properly trust and map the CoS values from the ACI fabric to the appropriate egress queues. If the CoS markings are not correctly configured on the IPN switches, application traffic can experience buffer drops and latency spikes even when the underlay has sufficient bandwidth and the APIC health scores are high. This is a common misconfiguration because the IPN switches are Layer 3 devices that require explicit QoS policies to preserve the ACI fabric's priority handling.
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 application servers are using different VLANs that are not stretched between pods.
The inter-pod network is not configured with enough bandwidth due to oversubscription.
Why it's wrong here
Oversubscription would cause sustained packet loss.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that underlay connectivity and MTU settings are sufficient for multi-pod performance, when in fact the IPN switches require explicit QoS configuration to preserve ACI's priority handling across pods.
Detailed technical explanation
How to think about this question
ACI uses a differentiated services code point (DSCP) to CoS mapping within the fabric, and the IPN switches must be configured with a QoS policy that maps these CoS values to the correct hardware queues (e.g., strict priority queue for latency-sensitive traffic). Without this mapping, all traffic may be placed into a single best-effort queue, causing delay and jitter for time-sensitive flows. In real-world deployments, this is often verified by checking the IPN switch's 'show mls qos' or 'show policy-map interface' output to ensure the ACI-generated CoS values are being honored.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
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.
Network — This question tests Network — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The CoS settings for the application traffic are not properly mapped to the appropriate queue on the IPN switches. — In a Cisco ACI multi-pod design, the IPN switches must properly trust and map the CoS values from the ACI fabric to the appropriate egress queues. If the CoS markings are not correctly configured on the IPN switches, application traffic can experience buffer drops and latency spikes even when the underlay has sufficient bandwidth and the APIC health scores are high. This is a common misconfiguration because the IPN switches are Layer 3 devices that require explicit QoS policies to preserve the ACI fabric's priority handling.
What should I do if I get this 350-601 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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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