Quick Answer
The answer is to restrict inbound SSH access to a specific IP range using a security group. This is correct because a bastion host serves as a single, hardened entry point to a private network, so it must expose only the minimal necessary port—typically TCP 22 for SSH—while using a security group to enforce network-layer least privilege. By limiting source IPs to a trusted range, you prevent brute-force attacks and unauthorized lateral movement from the internet. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this concept tests your understanding of bastion host security best practices within a layered defense strategy; a common trap is assuming a network ACL alone suffices, but security groups are stateful and easier to manage for host-level restrictions. Remember the mnemonic “Bastion = Block All, Trust Only SSH” to recall that the security group should deny all inbound traffic except SSH from a specific IP range.
This ANS-C01 practice question tests your understanding of network security, compliance and governance. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 TWO actions should be taken to secure an EC2 instance that is used as a bastion host? (Choose 2)
Use a security group that only allows necessary inbound ports
Minimize attack surface.
Use HTTPS instead of SSH for administration
Why wrong: HTTPS not for shell access.
Place the bastion host in a private subnet
Why wrong: Bastion host needs public access.
Restrict inbound SSH access to a specific IP range using security group
Limits exposure.
Allow all inbound traffic on port 22 in the network ACL
Why wrong: NACL is less secure than SG.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Use a security group that only allows necessary inbound ports
Option A is correct because a bastion host should only expose necessary inbound ports (typically TCP 22 for SSH) to minimize the attack surface. By using a security group that restricts inbound traffic to only required ports, you enforce the principle of least privilege at the network layer, preventing unauthorized access to other services that might be running on the instance.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Use a security group that only allows necessary inbound ports
Why this is correct
Minimize attack surface.
Related concept
Read the scenario before looking for a memorised answer.
Use HTTPS instead of SSH for administration
Why it's wrong here
HTTPS not for shell access.
Place the bastion host in a private subnet
Why it's wrong here
Bastion host needs public access.
Restrict inbound SSH access to a specific IP range using security group
Why this is correct
Limits exposure.
Related concept
Read the scenario before looking for a memorised answer.
Allow all inbound traffic on port 22 in the network ACL
Why it's wrong here
NACL is less secure than SG.
Common exam traps
AWS often tests the misconception that a bastion host should be placed in a private subnet for security, but the correct design requires it to be in a public subnet to serve as an entry point, with security group restrictions providing the necessary protection.
Detailed technical explanation
Security groups act as a stateful virtual firewall at the instance level, automatically allowing return traffic for permitted inbound rules, whereas NACLs are stateless and require explicit inbound and outbound rules. In practice, a bastion host is often placed in a public subnet with an Elastic IP, and its security group is configured to allow SSH only from trusted administrative IP ranges (e.g., your corporate VPN CIDR). This setup ensures that even if the instance has other services running, they remain inaccessible from the internet.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Network Security, Compliance and Governance — This question tests Network Security, Compliance and Governance — Read the scenario before looking for a memorised answer..
The correct answer is: Use a security group that only allows necessary inbound ports — Option A is correct because a bastion host should only expose necessary inbound ports (typically TCP 22 for SSH) to minimize the attack surface. By using a security group that restricts inbound traffic to only required ports, you enforce the principle of least privilege at the network layer, preventing unauthorized access to other services that might be running on the instance.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This ANS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the ANS-C01 exam.
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