200-901 Application Deployment and Security Practice Question
This 200-901 practice question tests your understanding of application deployment and security. 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 team is deploying a new microservice on Cisco Container Platform. The microservice needs to access a database hosted on a separate VM. The security policy requires that only the microservice can communicate with the database, and all traffic must be encrypted. The team is using Kubernetes network policies and mutual TLS. During testing, the microservice cannot reach the database. The database team reports that the database is reachable from other services. What is the most likely cause?
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
✓
A Kubernetes NetworkPolicy is blocking egress from the microservice pod to the database IP
The most likely cause is that a Kubernetes NetworkPolicy is blocking egress from the microservice pod to the database IP. Since the database is reachable from other services, the issue is specific to the microservice pod's network access. A NetworkPolicy that does not explicitly allow egress traffic to the database IP will default to denying that traffic, preventing the microservice from reaching the database even though the database itself is operational.
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.
✓
A Kubernetes NetworkPolicy is blocking egress from the microservice pod to the database IP
Why this is correct
Network policies can restrict traffic; a default deny or misconfigured policy could block the connection.
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.
✗
The database server is not listening on the expected port
Why it's wrong here
Since other services can reach the database, the listener is working.
✗
The mutual TLS certificates are expired or not trusted
Why it's wrong here
If mTLS were the issue, other services attempting to connect would also likely fail.
✗
The Istio sidecar proxy is misconfigured and rejecting traffic due to a missing ServiceEntry
Why it's wrong here
Without a ServiceEntry, traffic might be blocked by mutual TLS, but the symptom is unreachability, and other services work.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the default-deny behavior of Kubernetes NetworkPolicy, where candidates mistakenly assume that no policy means all traffic is allowed, but the trap is that once a policy selects a pod, all unallowed traffic is implicitly denied, including egress to external IPs.
Detailed technical explanation
How to think about this question
Kubernetes NetworkPolicy operates at the network layer (L3/L4) using iptables or eBPF rules to control ingress and egress traffic. By default, if any NetworkPolicy selects a pod, all traffic not explicitly allowed is denied. In this scenario, the microservice pod is likely selected by a NetworkPolicy that only allows ingress traffic or specific egress destinations, but not the database IP. This is a common pitfall when deploying microservices with strict network segmentation, as egress rules must be explicitly defined for external endpoints like VMs outside the cluster.
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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
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.
Application Deployment and Security — This question tests Application Deployment and Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: A Kubernetes NetworkPolicy is blocking egress from the microservice pod to the database IP — The most likely cause is that a Kubernetes NetworkPolicy is blocking egress from the microservice pod to the database IP. Since the database is reachable from other services, the issue is specific to the microservice pod's network access. A NetworkPolicy that does not explicitly allow egress traffic to the database IP will default to denying that traffic, preventing the microservice from reaching the database even though the database itself is operational.
What should I do if I get this 200-901 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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