This KCNA practice question tests your understanding of container orchestration. 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 Kubernetes cluster is experiencing network latency. The team suspects that the number of services and endpoints is causing iptables performance degradation. Which CNI plugin or network policy approach is most likely to improve performance?
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
✓
Use an eBPF-based CNI plugin like Cilium
C is correct because eBPF-based CNI plugins like Cilium bypass the traditional iptables chains entirely, using a kernel-level BPF (Berkeley Packet Filter) program to handle service load balancing and network policy enforcement. This eliminates the O(n) scaling issue of iptables rules with the number of services and endpoints, significantly reducing latency in large clusters.
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.
✗
Switch to Flannel with host-gw backend
Why it's wrong here
Flannel still uses iptables for policy enforcement, not addressing the issue.
✗
Use Calico with iptables mode
Why it's wrong here
Calico with iptables mode would not alleviate iptables performance issues.
✓
Use an eBPF-based CNI plugin like Cilium
Why this is correct
eBPF bypasses iptables, reducing latency and improving scalability.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Apply a default-deny NetworkPolicy
Why it's wrong here
NetworkPolicy does not affect the performance of iptables-based service routing.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume any CNI change or network policy adjustment can fix iptables performance, but only eBPF-based solutions fundamentally change the data path to avoid iptables scaling limitations.
Detailed technical explanation
How to think about this question
Under the hood, iptables rules are evaluated sequentially in a linear chain, so with thousands of services and endpoints, the kernel spends excessive time traversing rules for every packet. Cilium’s eBPF approach uses a hash table-based lookup in the BPF map, achieving O(1) complexity for service translation, and it can also offload packet processing to the XDP layer for even lower latency. In real-world scenarios, clusters with over 1,000 services often see 50-80% latency reduction when switching from iptables to eBPF-based CNI.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this KCNA question in full detail.
Container Orchestration — This question tests Container Orchestration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use an eBPF-based CNI plugin like Cilium — C is correct because eBPF-based CNI plugins like Cilium bypass the traditional iptables chains entirely, using a kernel-level BPF (Berkeley Packet Filter) program to handle service load balancing and network policy enforcement. This eliminates the O(n) scaling issue of iptables rules with the number of services and endpoints, significantly reducing latency in large clusters.
What should I do if I get this KCNA 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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