The correct minimal configuration is to deploy Azure Bastion in the hub VNet and ensure the spoke VNet is peered to the hub VNet. This works because Azure Bastion connects to VMs using private IPs over the Microsoft backbone, so it does not need to traverse the Azure Firewall or require public IPs on the spoke VMs; the VNet peering provides direct private IP connectivity between the Bastion host in the hub and the target VMs in the spoke. On the Microsoft Cybersecurity Architect exam, this scenario tests your understanding that Bastion is a platform-as-a-service (PaaS) resource that operates within its own subnet and relies on peering for cross-VNet access, not on firewall routing or public endpoints—a common trap is assuming the firewall must inspect Bastion traffic. Memory tip: “Bastion bypasses the firewall; peering provides the pathway.”
SC-100 Design security solutions for infrastructure Practice Question
This SC-100 practice question tests your understanding of design security solutions for infrastructure. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Your organization is planning to use Azure Bastion for secure RDP/SSH access to Azure VMs. You need to ensure that Bastion can reach the VMs in a spoke virtual network that is connected to a hub via VNet peering. The hub has an Azure Firewall. What is the minimal configuration required?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deploy Azure Bastion in the hub VNet. Ensure the spoke VNet is peered to the hub VNet.
Option D is correct because Azure Bastion does not require public IPs on VMs nor does it need to traverse the firewall; it uses private IPs and the Bastion host in the same or peered VNet. Option A is wrong because VMs do not need public IPs with Bastion. Option B is wrong because Bastion does not need to go through the firewall; it uses direct private IP connectivity. Option C is wrong because Bastion does not need a public IP on the VM.
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.
✗
Assign a public IP address to each VM. Deploy Azure Bastion in the hub VNet.
Deploy Azure Bastion in the spoke VNet. Configure Azure Firewall to allow traffic from Bastion to the VMs.
Why it's wrong here
Bastion can be in the spoke, but firewall rules are not needed because Bastion connects directly via private IP.
✗
Deploy Azure Bastion in the hub VNet. Ensure the spoke VNet has a route to the Bastion subnet.
Why it's wrong here
Bastion can be in the hub, but the spoke VNet needs to be peered, not a route. Bastion uses private IPs.
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 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 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: Deploy Azure Bastion in the hub VNet. Ensure the spoke VNet is peered to the hub VNet. — Option D is correct because Azure Bastion does not require public IPs on VMs nor does it need to traverse the firewall; it uses private IPs and the Bastion host in the same or peered VNet. Option A is wrong because VMs do not need public IPs with Bastion. Option B is wrong because Bastion does not need to go through the firewall; it uses direct private IP connectivity. Option C is wrong because Bastion does not need a public IP on the VM.
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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