The correct answer is to implement Kubernetes network policies and enable mTLS using a service mesh like Istio or Linkerd. This combination works because network policies act as a pod-level firewall, defining which pods can communicate with specific back-end services, while mutual TLS (mTLS) within a service mesh encrypts all pod-to-pod traffic, ensuring both authorization and confidentiality. On the Microsoft Cybersecurity Architect exam, this question tests your understanding of securing east-west traffic inside AKS clusters, a common scenario where candidates mistakenly choose Azure Firewall or NSGs—traps that control network boundaries but lack pod-level granularity and encryption. A key memory tip is to remember that network policies handle "who talks to whom," while mTLS handles "how they talk securely," and only a service mesh provides both together for pod-to-pod encryption.
SC-100 Design security solutions for infrastructure Practice Question
This SC-100 practice question tests your understanding of design security solutions for infrastructure. 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.
You are designing a secure solution for an Azure Kubernetes Service (AKS) cluster that hosts a critical application. You need to ensure that pods can only communicate with specific back-end services and that traffic is encrypted. What should you implement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Implement Kubernetes network policies and enable mTLS using a service mesh like Istio or Linkerd.
Option C is correct because network policies in AKS control pod-to-pod communication, and mutual TLS (mTLS) with a service mesh encrypts traffic. Option A is wrong because Azure Firewall controls ingress/egress, not pod-to-pod. Option B is wrong because NSGs are for subnet-level, not pod-level. Option D is wrong because App Gateway is for ingress.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Implement Kubernetes network policies and enable mTLS using a service mesh like Istio or Linkerd.
Why this is correct
Network policies restrict communication; mTLS encrypts it.
This handles external traffic, not internal pod communication.
✗
Deploy Azure Firewall and configure application rules.
Why it's wrong here
Azure Firewall does not enforce pod-level network policies.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this SC-100 question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SC-100 subnetting questions on CIDR, address ranges, and subnet selection.
Design security solutions for infrastructure — This question tests Design security solutions for infrastructure — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Implement Kubernetes network policies and enable mTLS using a service mesh like Istio or Linkerd. — Option C is correct because network policies in AKS control pod-to-pod communication, and mutual TLS (mTLS) with a service mesh encrypts traffic. Option A is wrong because Azure Firewall controls ingress/egress, not pod-to-pod. Option B is wrong because NSGs are for subnet-level, not pod-level. Option D is wrong because App Gateway is for ingress.
What should I do if I get this SC-100 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SC-100 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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