- A
DestinationRule with trafficPolicy.tls.mode set to ISTIO_MUTUAL
Configures client-side mTLS for traffic to a specific host.
- B
PeerAuthentication with mTLS mode set to STRICT
Enforces mTLS for workloads in the namespace.
- C
ServiceEntry with mTLS enabled for external services
ServiceEntry can define mTLS settings for external services.
- D
AuthorizationPolicy with deny rules for non-mTLS traffic
Why wrong: AuthorizationPolicy controls access based on identities, but does not enforce mTLS itself.
- E
NetworkPolicy with ingress rules to allow only TLS traffic
Why wrong: NetworkPolicy does not understand TLS; it operates at network layer.
Question 498 of 997
Enforce mTLS in Istio Service Mesh
This CKS practice question tests your understanding of minimize microservice vulnerabilities. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Which THREE of the following are valid ways to enforce mTLS in an Istio service mesh? (Select 3)
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
✓
DestinationRule with trafficPolicy.tls.mode set to ISTIO_MUTUAL
Option A is correct because a DestinationRule with `trafficPolicy.tls.mode` set to `ISTIO_MUTUAL` explicitly enforces mutual TLS for traffic to a specific host or subset, overriding the mesh-wide default. This ensures that both the client and server present certificates, providing strong identity-based authentication and encryption.
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.
- ✓
DestinationRule with trafficPolicy.tls.mode set to ISTIO_MUTUAL
Why this is correct
Configures client-side mTLS for traffic to a specific host.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
PeerAuthentication with mTLS mode set to STRICT
Why this is correct
Enforces mTLS for workloads in the namespace.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
ServiceEntry with mTLS enabled for external services
Why this is correct
ServiceEntry can define mTLS settings for external services.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
AuthorizationPolicy with deny rules for non-mTLS traffic
Why it's wrong here
AuthorizationPolicy controls access based on identities, but does not enforce mTLS itself.
- ✗
NetworkPolicy with ingress rules to allow only TLS traffic
Why it's wrong here
NetworkPolicy does not understand TLS; it operates at network layer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the distinction between mTLS enforcement (which requires proxy-level TLS configuration) and reactive policies (like AuthorizationPolicy) that only filter based on mTLS metadata, leading candidates to mistakenly select options that merely check for mTLS rather than enforce it.
Detailed technical explanation
How to think about this question
Under the hood, Istio’s mTLS enforcement relies on Envoy proxies performing TLS handshakes using SPIFFE-compliant certificates issued by the mesh CA. The `ISTIO_MUTUAL` mode in DestinationRule configures the client proxy to use mTLS, while PeerAuthentication with `STRICT` mode enforces that the server proxy rejects plaintext connections. A real-world scenario is a multi-cluster mesh where DestinationRules are needed to selectively enforce mTLS for cross-cluster services without affecting internal traffic.
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.
- →
Minimize Microservice Vulnerabilities — study guide chapter
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FAQ
Questions learners often ask
What does this CKS question test?
Minimize Microservice Vulnerabilities — This question tests Minimize Microservice Vulnerabilities — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: DestinationRule with trafficPolicy.tls.mode set to ISTIO_MUTUAL — Option A is correct because a DestinationRule with `trafficPolicy.tls.mode` set to `ISTIO_MUTUAL` explicitly enforces mutual TLS for traffic to a specific host or subset, overriding the mesh-wide default. This ensures that both the client and server present certificates, providing strong identity-based authentication and encryption.
What should I do if I get this CKS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
2 more ways this is tested on CKS
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which TWO of the following are valid methods to enforce mTLS in an Istio service mesh? (Select 2)
hard- A.Create a ServiceEntry for internal services
- B.Create a VirtualService with tls termination
- ✓ C.Create a PeerAuthentication resource with mtls.mode: STRICT
- D.Set global.mtls.enabled: true in IstioConfigMap
- ✓ E.Create a DestinationRule with tls.mode: ISTIO_MUTUAL
Why C: Option C is correct because a PeerAuthentication resource with `mtls.mode: STRICT` enforces mutual TLS at the service-to-service communication level within the Istio mesh. This setting ensures that all traffic between sidecar proxies uses mTLS, rejecting any plaintext connections, which directly minimizes the risk of unauthorized access or eavesdropping.
Variation 2. Which Istio resource is used to enforce mutual TLS (mTLS) for all services in a namespace, ensuring that traffic between services is encrypted?
hard- A.DestinationRule
- ✓ B.PeerAuthentication
- C.ServiceEntry
- D.VirtualService
Why B: PeerAuthentication is the correct Istio resource for enforcing mutual TLS (mTLS) at the namespace level. It defines the TLS mode for traffic between services, and when set to `STRICT`, it requires that all traffic within the namespace uses mTLS, encrypting both the request and response. This is part of Istio's security features under the `security.istio.io/v1beta1` API group.
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Last reviewed: Jul 4, 2026
This CKS practice question is part of Courseiva's free CNCF 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 CKS exam.
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