The answer is security group rules allowing SSH from the bastion to private instances, along with deploying the bastion host in a public subnet with an Internet Gateway. This design works because the bastion host acts as a controlled entry point: administrators connect from the internet to the bastion’s public IP, and the bastion then initiates SSH sessions to private instances using its private IP. The critical security layer is that private instances must have an inbound security group rule that explicitly permits TCP port 22 only from the bastion host’s security group or private IP, preventing any direct internet access to the private subnet. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of network segmentation and least-privilege access—a common trap is assuming a NAT Gateway or VPN is required, but the bastion itself handles forwarding. Memory tip: think of the bastion as a “guarded door”—the IGW opens the outer door, but the security group is the inner lock that only the bastion’s key can open.
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. 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.
A company has a VPC with public and private subnets. They want to implement a bastion host to allow secure SSH access to instances in private subnets. Which TWO components are required for this design?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A bastion host deployed in a public subnet
A bastion host must be deployed in a public subnet because it needs direct internet access via an Internet Gateway (IGW) to allow administrators to initiate SSH connections from the internet. The bastion then acts as a jump box, forwarding SSH traffic to private instances. Security group rules on the private instances must explicitly allow inbound SSH (TCP port 22) from the bastion host's private IP or security group, ensuring that only the bastion can reach them, not the internet directly.
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.
✓
A bastion host deployed in a public subnet
Why this is correct
Bastion must be publicly accessible.
Related concept
Read the scenario before looking for a memorised answer.
Already needed for public subnet, but not a specific component for bastion design.
✓
Security group rules allowing SSH from the bastion to private instances
Why this is correct
Controls access to private instances.
Related concept
Read the scenario before looking for a memorised answer.
✗
A Site-to-Site VPN connection to the VPC
Why it's wrong here
Not required; bastion provides secure access.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the misconception that a NATgateway is required for inbound SSH access to private instances, when in fact it only provides outbound internet access and cannot initiate inbound connections from the internet.
Detailed technical explanation
How to think about this question
Under the hood, the bastion host typically uses SSH agent forwarding or SSH tunneling to reach private instances, and its security group must allow inbound TCP 22 from trusted IP ranges (e.g., corporate VPNCIDR). The private instances' security group should reference the bastion's security group ID as the source, not a CIDR, to prevent any other host from initiating SSH. In real-world scenarios, organizations often harden the bastion by using a minimal AMI, disabling password authentication, and enabling detailed logging via AWS CloudTrail or VPC Flow Logs to audit all SSH sessions.
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 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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: A bastion host deployed in a public subnet — A bastion host must be deployed in a public subnet because it needs direct internet access via an Internet Gateway (IGW) to allow administrators to initiate SSH connections from the internet. The bastion then acts as a jump box, forwarding SSH traffic to private instances. Security group rules on the private instances must explicitly allow inbound SSH (TCP port 22) from the bastion host's private IP or security group, ensuring that only the bastion can reach them, not the internet directly.
What should I do if I get this ANS-C01 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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