- A
DestinationRule with trafficPolicy.tls.mode: ISTIO_MUTUAL
Why wrong: DestinationRule defines traffic policies for destination services, including TLS settings, but the mesh-wide mTLS is typically set via PeerAuthentication.
- B
PeerAuthentication with mTLS mode set to STRICT
PeerAuthentication defines the mTLS mode for workloads. Setting mode: STRICT enforces mTLS.
- C
VirtualService with tls configuration
Why wrong: VirtualService is for traffic routing, not TLS settings.
- D
ServiceEntry with mTLS enabled
Why wrong: ServiceEntry is for external services, not mesh-wide mTLS.
Question 215 of 997
Enforcing mTLS in Istio with PeerAuthentication
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.
A security engineer wants to enable mutual TLS (mTLS) between services in an Istio service mesh. Which Istio resource should be used to define the mTLS mode for the entire mesh?
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
✓
PeerAuthentication with mTLS mode set to STRICT
PeerAuthentication is the Istio resource specifically designed to define the authentication policy for workloads, including the mTLS mode. Setting `mTLS.mode: STRICT` in a PeerAuthentication policy enforces mutual TLS for all traffic within the mesh, ensuring that every service-to-service connection requires a valid client certificate. This is the correct resource for mesh-wide mTLS enforcement, as it operates at the authentication layer rather than the traffic routing layer.
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: ISTIO_MUTUAL
Why it's wrong here
DestinationRule defines traffic policies for destination services, including TLS settings, but the mesh-wide mTLS is typically set via PeerAuthentication.
- ✓
PeerAuthentication with mTLS mode set to STRICT
Why this is correct
PeerAuthentication defines the mTLS mode for workloads. Setting mode: STRICT enforces mTLS.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
VirtualService with tls configuration
Why it's wrong here
VirtualService is for traffic routing, not TLS settings.
- ✗
ServiceEntry with mTLS enabled
Why it's wrong here
ServiceEntry is for external services, not mesh-wide mTLS.
Common exam traps
Common exam trap: answer the scenario, not the keyword
A common pitfall in the CKS exam is confusing DestinationRule (which handles traffic routing and connection pool settings) with PeerAuthentication (which handles mTLS enforcement). Candidates often choose DestinationRule because it has a tls field, but for mesh-wide mTLS, PeerAuthentication with mode: STRICT is the correct resource.
Detailed technical explanation
How to think about this question
Under the hood, PeerAuthentication leverages the Istio Citadel component to issue SPIFFE-compliant certificates to each workload, and the STRICT mode configures the Envoy sidecar proxies to reject any incoming connection that does not present a valid client certificate. This is enforced at the proxy level via the `envoy.filters.network.rbac` filter and TLS context, ensuring that even if a workload is compromised, it cannot impersonate another service without the correct certificate. In a real-world scenario, a mesh-wide PeerAuthentication with STRICT mode is often combined with a DestinationRule for TLS settings to ensure consistent encryption, but the authentication policy alone governs the mTLS requirement.
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 CKS 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.
- →
Minimize Microservice Vulnerabilities — study guide chapter
Learn the concepts, then practise the questions
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Minimize Microservice Vulnerabilities practice questions
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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: PeerAuthentication with mTLS mode set to STRICT — PeerAuthentication is the Istio resource specifically designed to define the authentication policy for workloads, including the mTLS mode. Setting `mTLS.mode: STRICT` in a PeerAuthentication policy enforces mutual TLS for all traffic within the mesh, ensuring that every service-to-service connection requires a valid client certificate. This is the correct resource for mesh-wide mTLS enforcement, as it operates at the authentication layer rather than the traffic routing layer.
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
5 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. You are configuring an Istio service mesh for mTLS between services. Which resource defines the TLS mode for traffic between services in a namespace?
medium- ✓ A.PeerAuthentication
- B.ServiceEntry
- C.VirtualService
- D.DestinationRule
Why A: PeerAuthentication is the correct resource because it defines the TLS mode (e.g., STRICT, PERMISSIVE, DISABLE) for mTLS between services within a namespace in Istio. It enforces the authentication policy for workloads, ensuring that all traffic between them uses mutual TLS as specified. This directly controls the TLS mode for inter-service communication at the namespace or mesh level.
Variation 2. Which TWO of the following are valid ways to enable mTLS between services in a service mesh (e.g., Istio)?
medium- ✓ A.Creating a DestinationRule with a trafficPolicy that sets tls mode to ISTIO_MUTUAL
- B.Creating a ServiceEntry for the destination service
- C.Creating a NetworkPolicy that allows ingress on port 443
- ✓ D.Creating a PeerAuthentication resource with mTLS mode set to STRICT
- E.Creating an AuthorizationPolicy with DENY action
Why A: Option A is correct because a DestinationRule with `trafficPolicy.tls.mode: ISTIO_MUTUAL` explicitly configures the client-side proxy (Envoy) to use mutual TLS when sending requests to the destination service. This is the standard Istio mechanism to enforce mTLS at the service-to-service communication level, ensuring both client and server certificates are exchanged and verified.
Variation 3. You want to enable mutual TLS (mTLS) between services in a namespace using Istio. Which custom resource should you configure to enforce STRICT mTLS for all workloads in the namespace?
medium- A.DestinationRule with trafficPolicy.tls.mode: ISTIO_MUTUAL
- B.VirtualService with tls.mode: SIMPLE
- ✓ C.PeerAuthentication with mtls.mode: STRICT
- D.ServiceEntry with resolution: NONE
Why C: Option C is correct because PeerAuthentication is the Istio custom resource specifically designed to define traffic authentication policies between workloads. Setting `mtls.mode: STRICT` enforces that all traffic in the namespace must use mutual TLS (mTLS), rejecting any plain-text or non-mTLS connections. This is the standard way to enforce STRICT mTLS at the namespace level in Istio.
Variation 4. In an Istio service mesh, you want to enforce mutual TLS (mTLS) between services in a specific namespace. Which resource should you create to set the default mTLS mode to STRICT for all workloads in that namespace?
medium- ✓ A.PeerAuthentication
- B.VirtualService
- C.ServiceEntry
- D.DestinationRule
Why A: A PeerAuthentication resource in Istio defines the mutual TLS (mTLS) mode for workloads within a namespace. By setting the `mtls.mode` to `STRICT`, you enforce that all service-to-service communication in that namespace must use mTLS, rejecting any plain-text HTTP traffic. This is the correct resource for setting a namespace-wide default mTLS policy.
Variation 5. In an Istio service mesh, you want to enforce mutual TLS (mTLS) between all services in the 'default' namespace. Which resource should you create?
medium- ✓ A.PeerAuthentication with mTLS mode STRICT
- B.Sidecar resource with outboundTrafficPolicy REGISTRY_ONLY
- C.ServiceEntry with resolution NONE
- D.DestinationRule with trafficPolicy tls mode ISTIO_MUTUAL
Why A: To enforce mutual TLS (mTLS) between all services in the 'default' namespace, you create a PeerAuthentication resource with mTLS mode set to STRICT. This policy enforces that all traffic within the namespace must use mTLS, rejecting any plaintext connections. PeerAuthentication is the Istio resource specifically designed to define mTLS enforcement at the namespace or mesh level.
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Last reviewed: Jul 4, 2026
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