The answer is to deploy ExpressRoute with a site-to-site VPN as a failover. This solution satisfies the requirement for an encrypted hybrid network with high availability by combining a private, dedicated ExpressRoute circuit for primary traffic with an IPSec VPN gateway tunnel that activates automatically if the ExpressRoute link fails. On the Microsoft Cybersecurity Architect exam, this scenario tests your understanding of layered resilience and encryption—specifically that ExpressRoute alone does not encrypt data by default, so the VPN failover provides both encryption and redundancy, eliminating any single point of failure. A common trap is choosing ExpressRoute only, forgetting its lack of native encryption, or selecting a site-to-site VPN alone, which lacks the private dedicated connection. For a memory tip, think “ExpressRoute for speed, VPN for safety”—the dedicated line handles performance, while the encrypted VPN backup ensures continuity and security.
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 hybrid network for a multinational company. They require encrypted communication between on-premises data centers and Azure, with high availability and no single point of failure. Which solution should you recommend?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deploy ExpressRoute with a site-to-site VPN as a failover.
Option B is correct because ExpressRoute with a VPNgateway failover provides a private dedicated connection with encrypted site-to-site VPN as backup, meeting high availability and encryption. Option A is wrong because site-to-site VPN alone lacks the private dedicated connection. Option C is wrong because Azure Virtual WAN is a networking service, not a specific connectivity solution, and point-to-site VPN is for remote users. Option D is wrong because ExpressRoute does not encrypt traffic by default; encryption must be added separately.
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.
✓
Deploy ExpressRoute with a site-to-site VPN as a failover.
Why this is correct
ExpressRoute provides a private, dedicated connection; VPN failover ensures high availability and encryption.
Related concept
Static NAT maps one inside address to one outside address.
✗
Deploy a site-to-site VPN over the internet with two active VPN devices.
Why it's wrong here
VPN over the internet may have latency and reliability issues compared to a private connection.
✗
Deploy Azure Virtual WAN with point-to-site VPN for each data center.
Why it's wrong here
Point-to-site VPN is for individual clients, not data center connections.
✗
Deploy ExpressRoute without encryption and rely on Microsoft backbone security.
Why it's wrong here
ExpressRoute traffic is not encrypted by default; encryption is required for compliance.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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: Deploy ExpressRoute with a site-to-site VPN as a failover. — Option B is correct because ExpressRoute with a VPN gateway failover provides a private dedicated connection with encrypted site-to-site VPN as backup, meeting high availability and encryption. Option A is wrong because site-to-site VPN alone lacks the private dedicated connection. Option C is wrong because Azure Virtual WAN is a networking service, not a specific connectivity solution, and point-to-site VPN is for remote users. Option D is wrong because ExpressRoute does not encrypt traffic by default; encryption must be added separately.
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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