The answer is to use X.509 certificates with Azure Device Provisioning Service (DPS) for automatic enrollment and certificate rotation. This design is correct because X.509 certificates provide strong, mutual TLS authentication for device-to-cloud communication, while DPS enables automatic enrollment and streamlined certificate rotation without manual intervention—critical for devices on a private network with limited internet access. On the Microsoft Cybersecurity Architect exam, this scenario tests your understanding of IoT device authentication and credential lifecycle management, often appearing as a trap where candidates confuse network security tools like Azure Firewall with authentication mechanisms. A common mistake is choosing SAS tokens, which require manual rotation and are less secure, or managed identities, which are designed for Azure resources, not IoT devices. Remember the key distinction: DPS handles the provisioning and rotation of X.509 certificates automatically, ensuring both authentication and encryption are maintained over TLS. Memory tip: “X marks the spot for DPS rotation”—X.509 certificates plus DPS automate the secure handshake and credential refresh.
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 access solution for a manufacturing company's IoT devices that send telemetry to Azure IoT Hub. The devices run on a private network with no internet access except through a firewall. You need to ensure that device-to-cloud communication is authenticated and encrypted, and that device credentials are rotated regularly. What should you include in the design?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use X.509 certificates with Azure Device Provisioning Service (DPS) for automatic enrollment and certificate rotation.
Option A is correct because X.509 certificates with auto-enrollment via DPS provide strong authentication, encryption (TLS), and automated certificate rotation. Option B is incorrect because SAS tokens require manual rotation and are less secure. Option C is incorrect because managed identities are for Azure resources, not IoT devices. Option D is incorrect because Azure Firewall is a network security component, not an authentication mechanism.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Configure Azure Firewall to authenticate and encrypt device traffic.
Use X.509 certificates with Azure Device Provisioning Service (DPS) for automatic enrollment and certificate rotation.
Why this is correct
X.509 certificates meet authentication, encryption, and rotation requirements.
Related concept
Static NAT maps one inside address to one outside address.
✗
Use shared access signature (SAS) tokens with a central key management system.
Why it's wrong here
SAS tokens require manual management and rotation.
✗
Assign managed identities to each IoT device.
Why it's wrong here
Managed identities are not supported for IoT devices.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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 the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SC-100 NAT questions on configuration and troubleshooting.
Design security solutions for infrastructure — This question tests Design security solutions for infrastructure — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Use X.509 certificates with Azure Device Provisioning Service (DPS) for automatic enrollment and certificate rotation. — Option A is correct because X.509 certificates with auto-enrollment via DPS provide strong authentication, encryption (TLS), and automated certificate rotation. Option B is incorrect because SAS tokens require manual rotation and are less secure. Option C is incorrect because managed identities are for Azure resources, not IoT devices. Option D is incorrect because Azure Firewall is a network security component, not an authentication mechanism.
What should I do if I get this SC-100 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SC-100 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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