The answer is a route-based VPN gateway, a local network gateway, and a virtual network gateway. A route-based VPN gateway is required for Azure site-to-site VPN in hybrid networks because it uses dynamic routing with BGP and supports IKEv2, enabling automatic failover and policy-based traffic selectors without static route limitations. The local network gateway defines the on-premises VPN device’s public IP and address space, while the virtual network gateway sits in Azure to terminate the encrypted tunnel. On the Microsoft Cybersecurity Architect exam, this question tests your understanding of the core components needed for a secure hybrid network—common traps include confusing policy-based gateways (which lack BGP and failover) with route-based ones. A helpful memory tip: think “three gateways for three connections”—the on-premises device, the local network gateway definition, and the Azure virtual network gateway form the essential triad for a resilient site-to-site VPN.
SC-100 Design security for infrastructure Practice Question
This SC-100 practice question tests your understanding of design security 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.
Which THREE components are required to implement a secure hybrid network with Azure using a site-to-site VPN?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
VPN gateway (route-based)
A route-based VPNgateway (option C) is required for site-to-site VPN connections because it uses dynamic routing (BGP) and supports IKEv2, enabling automatic failover and policy-based traffic selectors. This is essential for secure hybrid networking as it allows Azure to route traffic to on-premises networks via the VPN tunnel without static route limitations.
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.
✗
Public IP address for the VPN device
Why it's wrong here
While a public IP is needed for the on-premises device, it's not a component in Azure; the local network gateway represents it.
✗
ExpressRoute circuit
Why it's wrong here
ExpressRoute is a dedicated private connection, not a VPN component.
✓
VPN gateway (route-based)
Why this is correct
Required for the Azure side of the VPN connection.
Related concept
Read the scenario before looking for a memorised answer.
Read the scenario before looking for a memorised answer.
✓
Local network gateway
Why this is correct
Represents the on-premises VPN device and its public IP.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse the VPNgateway (the Azure resource) with the Virtual Network Gateway (the parent resource type), or mistakenly think a public IP is a separate component when it is actually a property of the VPN gateway, leading them to select option A instead of recognizing that the three required components are the VPN gateway, Virtual Network Gateway, and Local Network Gateway.
Detailed technical explanation
How to think about this question
A route-based VPNgateway uses Virtual Network Gateway (option D) as the Azure-side endpoint, which must be deployed in a dedicated gateway subnet with a /27 or larger CIDR. The Local Network Gateway (option E) represents the on-premises VPN device's public IP and address space, enabling the VPN gateway to establish IPsec tunnels with IKEv2 and BGP for dynamic route exchange. In production, this setup supports active-active mode for high availability, where two instances of the gateway handle failover transparently.
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 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.
Design security for infrastructure — This question tests Design security for infrastructure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: VPN gateway (route-based) — A route-based VPN gateway (option C) is required for site-to-site VPN connections because it uses dynamic routing (BGP) and supports IKEv2, enabling automatic failover and policy-based traffic selectors. This is essential for secure hybrid networking as it allows Azure to route traffic to on-premises networks via the VPN tunnel without static route limitations.
What should I do if I get this SC-100 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.
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Question Discussion
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